WO2005077405A1

WO2005077405A1 - Compositions and methods for the treatment of cancer by systemic elevation of lactate and consequent depletion of arginine

Info

Publication number: WO2005077405A1
Application number: PCT/US2005/003468
Authority: WO
Inventors: Slobadan Tepic
Original assignee: Cancer Treatment International; Robert, Lev
Priority date: 2004-02-06
Filing date: 2005-02-07
Publication date: 2005-08-25

Abstract

Compositions and methods for the treatment of cancer by systemic depletion of arginine, a semi-essential amino acid, whereby the depletion is effected by, and only by, restriction of all sources of arginine, as well as by concurrent control over circulating ornithine and citrulline. Acute treatment sessions include maximal reduction of nutritional intake of arginine, inhibition of net arginine inflow from protein turnover, and elimination of arginine production by intestinal bacteria by sterilization of the gut with suitable antibiotics. Disturbances of blood clotting mechanisms and of hemodynamics are minimized by the administration of a nitric oxide donor and a vasoconstricting peptide.

Description

COMPOSITIONS AND METHODS FOR THE TREATMENT OF CANCER BY SYSTEMIC ELEVATION OF LACTATE AND CONSEQUENT DEPLETION OF ARGININE

FIELD OF THE INVENTION The present invention relates to compositions and methods for the treatment of cancer. The present invention is more particularly related to compositions and methods for the treatment of cancer through the systemic elevation of lactate, thus enabling systemic depletion of arginine, a semi-essential amino acid, whereby the depletion is effected by, and only by, restriction of all sources of arginine. The invention further relates to compositions and methods for the treatment of cancer by the systemic depletion of free arginine in a patient's body from extracellular pools down into micromolar range, thus bringing about the conditions needed for an effective attack on cancer. Concurrent control over circulating ornithine and citrulline may be equally important and achievable with the same measures.

DEFINITION OF TERMS

Acute lymphocytic leukemia (ALL) - a type of childhood leukemia, which responds well to asparaginase treatment.

Arginase (ARG) - converts L-arginine and H₂O to L-ornithine and urea; found at high concentrations in the liver; other isoforms widely distributed in basically all tissues of all animals, but also in plants and bacteria.

Arginine - an essential amino acid (L-arginine); by some accounts considered semi- essential, since it can be produced from for example citrulline, which in turn can be produced from praline or glutamine. All amino acids have optical (or stereo) isomers, D and L, and so does arginine. Proteins consist exclusively of L-amino acids, and in this text, if not specified, L-form is implied.

Arginine decarboxylase (ADC) - converts L-arginine to agmatine and CO .

Arginine deiminase (ADI) - converts L-arginine and H₂O to L-citrulline and NH₃. Arginine kinase (AK) - converts L-arginine and ATP to N^ω-phosphor-arginine and ADP.

Asparaginase - converts L-asparagine and H 0 to aspartate and NH₃ (drug approved for the treatment of ALL).

Asparagine - L-asparagine, a non-essential amino acid.

Catch-22 - a 1961 book by Joseph Heller, which also became a widely excepted English expression defining a problem with no solution, a difficulty defying an exit strategy.

cAMP - cyclic adenosine monophosphate; plays an important role in prevention of calcium influx into thrombocytes; its production is stimulated by prostacyclin.

cGMP - cyclic guanosine monophosphate; plays an important role in prevention of calcium influx into thrombocytes; its production is stimulated by NO.

Desmopressin - an analog of vasopressin (approved drug).

Disseminated intravascular coagulation (DIC) - an extreme form of pathological coagulation, leading to massive clot formation, and, subsequently to platelet depletion and to increased risk of (internal) bleeding.

Hepatocellular carcinoma - a predo inant type (about 90% of all cases) of primary liver cancer. Hepatitis B and C are considered main causative factors. Endemic in many Asian and African countries, accounting for perhaps as many as 1.3 million annual cancer deaths worldwide (according to WHO, 25 '000 in Europe; 5 '000 in the US;

30O00 in Japan). Hepatocellular carcinomas are very responsive to arginine depletion.

Iloprost - an analog of prostacyclin (approved drug).

Insulin / glucose-clamp - a therapeutic composition, most frequently used as a diagnostic tool for determining insulin resistance in diabetes; a dose of insulin (usually administered as a primed, fixed-rate continuous infusion) is balanced by a variable dose of glucose required to maintain its normal plasma concentration (by feedback control); hence the name: glucose-clamp (also euglycemic insulin clamp).

Intestinal-renal axis - a biochemical pathway for endogenous production of arginine, whereby citrulline is produced in the small intestine from non essential amino acids proline, glutamine or glutamate via ornithine and then converted to arginine by mostly kidneys.

Melanoma - a highly invasive cancer, usually of cutaneous origin. Excessive exposure to sunlight is a major risk, and the most important factor in the rapidly rising incidence of melanoma. Early surgical treatment is very effective; overall 5-year survival rate is about 80%. Melanomas are very sensitive to arginine depletion, and generally unable to substitute citrulline for arginine because they fail to produce the required enzymes (ASS and ASL).

Nitric oxide (NO) - a ubiquitous signaling molecule with different physiological functions, including vasodilation and inhibition of platelet activation.

Nitric oxide synthase (NOS) - converts L-arginine and oxygen to citrulline and NO (the stoichiometry not clear), found in different forms and in different cell types.

Nitric oxide donor - compounds which release NO, either directly, or via metabolic conversions of certain substrates.

Nitroglycerin - an indirect NO donor; a drug approved for treatment of heart disease, particularly angina pectoris.

Ornipressin - an analog of vasopressin with ornithine substituted for arginine, vasoconstrictor (approved drug).

Pegylation - process of covalent attachment of PEG molecules to selected amino acid side chains of a protein, which leads to increased circulation time and reduced immunogenicity.

Polyethyleneglycol (PEG) - polymer of ethyleneglycol, characterized by high affinity for water. Prostacyclin - prostaglandin I₂, potent inhibitor of platelet aggregation.

Sodium nitroprusside (SNP) - decomposes to NO and cyanide; a direct NO donor; a drug approved for treatment of hypertension.

Terlipressin - an analog of vasopressin (approved drug).

Therapeutic composition - a multi-component drug, whereby single components

(active ingredients) are either mixed together by the producer, or by the physician prior to application, or kept and delivered separate to the patient during a given treatment session.

Urea cycle - a set of enzymes, residing in liver, which convert arginine to ornithine to citrulline back to arginine via arginino-succinate; its physiological function is conversion of excess nitrogen to urea, which is then excreted by kidneys.

Vasopressin - posterior pituitary hormone, anti-diuretic hormone, an arginine- containing peptide, also an approved drug.

BACKGROUND Treatment of cancer by limiting the supply of an amino acid has been known and practiced in clinical oncology since the seventies, following the discovery of the unusual sensitivity of the acute lymphocytic (lymphoblastic) childhood leukemia (ALL) to restriction of asparagine. The sensitivity is due to suppressed asparagine synthesis in ALL cells. However, usefulness of asparaginase remained limited to ALL, which also was found to become resistant to repeated treatments. Leukemia cells surviving the initial period of depletion eventually activate their own, normally latent, synthesis of asparagine, a non-essential amino acid. Asparaginase is thus usually used for induction in a multi-drug chemotherapy regimen for ALL, which at approximately 75% cure rate is one of the best treatments for any disseminated cancer. Depletion of an essential amino acid would make it impossible for cells to become resistant, and a number of in vitro experiments performed over the last three decades have shown that withdrawal of an essential amino acid can in fact kill cancer cells more readily than healthy ones. Depletion of arginine, of all essential amino acids, is most effective and most selective in eliminating cancer cells versus their healthy counterparts. While this unusual effectiveness of arginine depletion is not fully understood, it almost certainly is a consequence of the many different metabolic roles which arginine plays, on both systemic and cellular levels. Arginine is a substrate for a number of enzymes, widely distributed in different tissue and cell types.

Polyamine synthesis, present in all cells, and increased in proliferation, relies on conversion of arginine to ornithine by arginase (ARG) of so-called type II. The same reaction is catalyzed by arginase of type I within the urea cycle, localized in the liver. The urea cycle is responsible for conversion of ammonia into urea, the dominant path for elimination of excess nitrogen.

Arginine is also a substrate for nitric oxide synthase (NOS), which converts arginine into citrulline and nitric oxide (NO). There are several types of NOS, reflecting the wide-ranging and very important roles of nitric oxide (NO). One of these roles is maintenance of platelet inactive state, mostly by NO produced by the vascular endothelium. NO stimulates production of cyclic guanosine monophosphate (cGMP) in platelets in their inactive state. Removal of NO signal leads to depletion of cGMP, and then, through a number of molecular events, to influx of calcium and platelet activation. Prostacyclin has a similar, synergistic, role of platelet inactivity maintenance by stimulation of cyclic adenosine monophosphate (cAMP) production. The main source of prostacyclin is also vascular endothelium. Half-lifes of both NO and prostacyclin are extremely short, measured in seconds, explaining why even a brief exposure of platelets to an environment lacking constant production of these two molecules, leads to platelet activation and rapid clot formation. NO is also a potent vasodilator. Blood vessel lumen is under constant control by agonist / antagonist actions of NO and so-called pressor peptides all of which contain arginine (vasopressin, angiotensins). Normal function of the heart, and its impact on the circulation of blood, referred to as hemodynamics, depends on the appropriate volume of the blood and the peripheral resistance of the complete vascular system. The heart's own feedback control will respond to a potential drop in pressure, due to either reduced blood volume, or reduced peripheral resistance, increasing the pulse rate, even before a measurable pressure drop is registered at the periphery. The early workers on essential amino acid depletion for cancer could have not understood multiple dependencies of hemodynamic stability on the substances, which either contain arginine, or are produced from it. NO is a "modern" molecule, perhaps the most intensely studied one in the last decade.

Arginine is also a substrate for arginine decarboxylase (ADC), which converts arginine to agmatine. ADC is present in the brain and kidneys of mammals, but the metabolic role of agmatine remains rather poorly understood. Three additional enzymes are known which utilize arginine as a substrate: arginine kinase, arginine 2-monooxigenase and glycine amidinotransferase.

In view of the amounts of these different enzymes and their activity in transformed cells, the most likely culprit for the high rate of arginine consumption by cancer cells in comparison to normal cells is arginase type II . The rate at which arginine is used for production of polyamines in cancer cells appears to lead to local, intracellular depletion of arginine, which then affects overall protein synthesis and thus cells' viability. This may explain why the cancer-killing window for arginine depletion opens at between 10 and 1 micromolar (extracellular concentration), while other essential amino acids need many-fold lower concentrations and longer depletion times for a similar effect.

Effectiveness of arginine depletion in selective killing of cancer cells in vitro seems thus to be the result of the unique position which arginine occupies in the metabolic processes on cellular and systemic level. Transfer of arginine depletion from in vitro to in vivo conditions has required solving a number of puzzles and problems posed by arginine metabolic functions.

The first problem is caused by homeostatic responses at the systemic level, initiating a, potentially, massive protein breakdown, mostly of muscle tissue, in order to replenish arginine to its base-line level (of about 80 to 100 micromolar in plasma). Attempting to overcome this response by higher rates of arginine removal via enzymatic degradation, would lead to a life-threatening condition with ammonia accumulation. Since protein breakdown leads to influx of all of the amino acids, and only arginine is targeted for removal, concentrations of other amino acids tend to increase. In fact, the non-essential ones are allowed to increase, but most of the essential ones are catabolized to their respective base-line concentrations. This floods the body with ammonia, which is the final form in which nitrogen is released from each of the amino acid molecules degraded. Removal of ammonia so generated, however, requires an increased conversion rate by the urea cycle, which, for that, unfortunately, needs an elevated concentration of arginine. Whilst enzymes of the urea cycle hold pretty tight onto the cycle intermediaries (arginine, ornithine, citrulline, and arginino succinate), the cycle activity still depends on the general availability of these substrates. Hence Catch-22 of arginine depletion: reduction of arginine concentration leads to increased generation of ammonia, which needs higher concentration of arginine to be effectively cleared from the body. The solution to the problem, ultimately enabling arginine depletion, was found in inhibiting this homeostatic response of the protein breakdown by, for example, insulin (Tepic, S., Pyk, P., "Arginine decomposing enzyme therapeutic composition", USP 6,261,557, 2001).

However, depletion of arginine suppresses NO production. Ensuing platelet activation leads to clot formation, loss of platelets and subsequently, to internal bleeding. In experimental dogs, the bleeding usually starts by the second or third day of depletion. There is also an increased risk of generalized, rapid platelet activation; potentially leading to disseminated intravascular coagulation (DIC), a difficult-to-treat, and life-threatening condition. Transfusion of platelet-enriched plasma is only a temporary measure, leading to a new round of clotting and further damage to vital organs. Kidneys, lungs and the liver are the primary sites of clot entrapment ~ their failure a common cause of death. Systemic levels of NO can be restored by continuous delivery of one of the known NO donors. However, restoring NO supply, in an arginine depleted state, leads to excessive vasodilatation for the lack of normal pressor counterbalance (since all of pressor peptides contain arginine and thus cannot be produced at normal rates). This difficulty can be resolved by supplying a pressor peptide, for example vasopressin, or one of its more stable analogs, such as ornipressin, terlipressin or desmopressin.

However, after a day or two of strict arginine depletion, lack of another important molecule becomes a limiting factor in the maintenance of normal blood circulation. While arginine is not directly involved in synthesis of prostacyclin, arginine depletion suppresses prostacyclin production in an indirect way. In fact, it is generally expected that in such a metabolic stress, all cells will gradually revert to their own survival, dismantling production of all, but the most crucial "export" substances. Shortage of circulating prostacyclin also leads to platelet activation and all of the sequelae. The problem is solved by administration of prostacyclin, or one of its more stable analogs, such as iloprost (Tepic, S., "Therapeutic composition for treatment of cancer by arginine depletion", WO 03/063780, based on USPO application 60/350,971, filed 2002, pending).

Arginine is a semi-essential amino acid, i.e. the body is capable of producing some, but usually not all of the required arginine from non-essential amino acids as the precursors, namely from proline and glutamine / glutamate. The relative need for endogenous sources of arginine varies with age and animal species. For example, milk of many mammals, including humans, is a poor source of arginine and neonates are very much dependent on endogenous production of arginine via so-called intestinal-renal axis, whereby citrulline is produced by mostly small intestine and then converted to arginine by mostly kidneys. Use of glutamine / glutamate as a substrate for production of citrulline decreases progressively in neonatal period, leaving proline as the dominant precursor for citrulline synthesis in adults.

Tight control of circulating arginine is subject to restriction of all possible sources: (1) exogenous through food intake; (2) endogenous through protein breakdown; and (3) endogenous through conversion of mostly proline to arginine via pyrroline-5-carboxylate, ornithine and citrulline (in the intestine), and argininosuccinate (in the kidneys). SUMMARY The invention discloses compositions and methods for the treatment of cancer by systemic depletion of arginine, a semi-essential amino acid, whereby the depletion is effected by, and only by, restriction of all sources of arginine. The surprising discovery by this inventor, which is the basis of this patent application, is that the body, by itself, will deplete free arginine from extracellular pools down into micromolar range, and hence bring about the conditions needed for an effective attack on cancer. Concurrent control over circulating ornithine and citrulline is just as important and is achievable with the same measures.

During an acute treatment session, lasting up to a week, but for certain cancers as short as two to three days, nutritional intake of arginine is maximally reduced; net arginine inflow from the turnover of dispensable body proteins is inhibited by stimulation of endogenous production of insulin through consumption of carbohydrates and/or by pharmacological intervention with insulin, insulin-glucose clamp, or insulin like growth factor one (IGF-I); while the intestinal-renal axis is inhibited by, preferably, elevation of lactate, preferably, via oral intake of L-lactic acid / L-lactate(s). Further, yet, production of arginine by intestinal bacteria is eliminated by sterilization of the guts with suitable antibiotics.

Even such a transient state of arginine depletion can lead to serious side effects, particularly to disturbances of blood clotting mechanisms and of hemodynamics. Remedies have been discovered by this inventor and disclosed in other patent pending applications, all of which are hereby incorporated by reference. As a minimum, a nitric oxide donor and a vasoconstricting peptide should be used during the session of arginine depletion.

DETAILED DESCRIPTION OF THE INVENTION The surprising discovery by this inventor, which is the basis of this patent application, is that if sufficient control is exercised over arginine inflow from these three sources, the body, by itself, will deplete free arginine from extracellular pools down into micromolar range, and hence bring about the conditions needed for an effective attack on cancer. Concurrent control over circulating ornithine and citrulline is just as important and is achievable with the same measures.

A case report by Byrd et al. (Byrd D J, Krohn H -P, Winkler L, Steinborn C, Hada M, Brodehl J, and Hunneman D H, "Neonatal pyruvate dehydrogenase deficiency with lipoate responsive lactic acidaemia and hyperammonaemia", European Journal of Pediatrics, Vol.148:543-547, 1989) described physiological abnormalities due to an enzymatic deficiency in the metabolism of lactate: lactic acidosis (ultimately due to reduced production of bicarbonate from lactate); severe deficiency of citrulline and arginine (at below detection in plasma); and hyperammonaemia (due to lack of arginine and thus ineffective, if intact urea cycle enzymes). Use of emergency measures, including dialysis to remove ammonia, in the first days of the baby's life kept her alive in spite of complete depletion of arginine. Supplementing other medications with arginine, initiated at day nine, led to normalization of ammonia and she lived for a year and a half.

Biochemical explanations for the observations of this case report followed ten years later, published in the paper by Dillon et al. (Dillon E L, D. Knabe A, and Wu G, "Lactate inhibits citrulline and arginine synthesis from proline in pig enterocytes", American Journal of Physiology -Gastrointestinal and Liver Physiology, Vol. 276, Issue 5, G1079-G1086, May 1999): increased concentration of lactate inhibited proline oxidase, an enzyme upstream in the endogenous production of arginine via so-called intestinal-renal axis, whereby citrulline is produced in the small intestine from non- essential amino acids and converted to semi-essential arginine by mostly kidneys.

Milk diet, relatively poor on arginine, coupled with inhibition of the endogenous production of arginine and a high demand on protein synthesis in a newborn, had conspired to throw this baby into a state of near total systemic depletion of arginine and citrulline, its intermediary in the urea cycle.

This inventor and researcher, as well as many others involved in development of cancer treatments by arginine depletion in the past several decades have been motivated by in vitro experiments, which had demonstrated that a number of cancer cell lines will not survive past several days of deep (into micromolar) depletion of arginine. The difficulty is in attaining such a state of depletion in vivo.

The prevailing approach has been systemic deployment of an arginine degrading enzyme, which should effectively remove arginine released into circulation from any one of the potential sources (Tepic, S., Pyk, P., "Arginine decomposing enzyme therapeutic composition", USP 6,261,557, 2001; Clark, M. , "Modified arginine deiminase", USP 6,737,259; Takaku, K., et al., "Arginine deiminase from a mycoplasma arginini strain", USP 5,474,928). The surprising discovery of this inventor, arrived at in the course of experimental work on animals, inspired by the above cited case report of Byrd et al., is that arginine depletion can be achieved without any intervention aiming at direct arginine removal, such as chemical-enzymatic or physical, via e.g. dialysis.

Effective restriction of arginine inflow from all major sources, coupled with stimulated, but normal, physiological use of arginine can in fact lead to its thorough (into micromolar) elimination from circulation.

Hence the cancer treatment of this invention, constituting the following therapeutic interventions: (A) inhibition of endogenous arginine production from the intestinal-renal axis by elevation of systemic lactate to several times the normal level, preferably to 5 to 15 millimolar in blood; (B) inhibition of protein breakdown and stimulation of protein synthesis by, for example, insulin or insulin-like growth factors, specifically IGF-I; (C) elimination of intestinal bacteria, an effective source of arginine; (D) restriction of arginine supply via nutrition; (E) provision of nitric oxide from a nitric oxide donor, preferably percutaneously; (F) provision of a pressor peptide, preferably via nasal route; (G) provision of prostacycline, or an analog of prostacycline, e.g. iloprost;

RATIONALE / EXECUTION Interventions (A) through (D) are enabling; (E) through (G) are controlling side effects of arginine depletion.

Inhibition of endogenous production of citrulline / arginine via intestinal-renal axis, (A), by elevated lactate is preferred over, but does not exclude other known means, such as by glycylglycine derivative of delta-N-(phosphonacetyl)-L-ornithine (Gly-Gly- PALO), a powerful and specific inhibitor of ornithine transcarbamylase. Lactate- mediated inhibition can be accomplished with simple substances and using the simplest mode of delivery, frequent oral intake of L-lactic acid / L-lactate(s) (potassium, magnesium, sodium or calcium). This will make delivery of this treatment feasible even under the prevailing conditions in the undeveloped world regions where, for example, hepatocellular carcinoma, worldwide number one cancer killer (1.3 million per year) and the best responder to arginine depletion, is endemic - the Far East of Asia and Sub- Saharan Africa.

Normal concentration of lactate in the blood is 1 to 2 millimolar. The work of Dillon et al. referenced above, and my own experiments in dogs, have shown that concentrations of 5 to 15 millimolar are effective in suppressing intestinal-renal axis and consequently lowering concentration of arginine. A mixture of L-lactic acid and (potassium, magnesium, sodium or calcium) L-lactate can also be delivered i.v., adjusting the ratio of the two so as to keep the blood pH within normal limits. However, oral intake is the preferred mode of delivery. Alternatively, a gastric feeding tube and a pump, can be used to guarantee continuous delivery of the desired dose.

There are a number of natural sources of L-lactic acid, preferable to the synthetic compound, for example, milk whey. Even though relatively low on protein, which also contains a relatively small percentage of arginine, milk whey should preferably be cleared of any protein. Addition of a buffer, e.g. calcium lactate or bicarbonate may be of a benefit.

Another form of lactic acid useful for the purpose, is oligomeric, or a low molecular weight, e.g. approx. 1500 Dalton, polylactic acid. In this form, it is not water soluble, hence not acidic, yet by hydrolysis in the gastric tract it becomes available for uptake by the small intestine where its function is to be exerted.

Deployment of insulin, (B), was one of the crucial achievements of this inventor in his efforts to achieve systemic, deep and sustained arginine depletion in vivo. Insulin stimulates production of proteins and inhibits their breakdown, the net effect leading to intended reduction of free arginine. Use of insulin calls for an increased intake of sugar in order to maintain normal levels of blood glucose. IGF-I is an even more potent growth factor than insulin, but at this time, it is not a registered drug. In vitro, we have shown that addition of IGF-I to leukemia cell cultures placed in arginine-free medium has led to complete elimination within three days of even the most tenacious, rare survivors of arginine depletion alone.

Intestinal bacteria are a significant source of arginine and prior to increasing lactate for arginine depletion, the guts should be sterilized by antibiotics, (C), preferably non-absorbing, i.e. by those which remain in the intestinal lumen after oral delivery, e.g. gentamicin and/or vancomycin. It is self-evident that intake of protein should be maximally reduced, as suggested, (D), at least of protein rich in arginine.

Depletion of arginine, enabled by interventions (A) through (D), suppresses production of nitric oxide (NO). Ensuing platelet activation leads to clot formation, loss of platelets and subsequently, to internal bleeding. Systemic levels of NO can be restored during the period of arginine depletion by continuous delivery of one of the NO donors, preferably percutaneously, (E). Nitroglycerine is the most common of all NO donors, but in this application, isosorbide dinitrate (ISDN) is preferred. ISDN formulations for percutaneous delivery are commonly available and prefered over other delivery modalities.

Restoring NO supply, in arginine depleted state, leads to excessive vasodilatation for the lack of normal pressor counterbalance, since all of pressor peptides contain arginine and thus cannot be produced at normal rates. This difficulty can be resolved by administering a pressor peptide, (F), preferably vasopressin, or one of its analogs, and preferably via nasal route.

In shorter sessions of up to three days, prostacycline may not be needed, but should the type of cancer call for a longer session of up to seven days, prostacycline or its stable analog, iloprost, should be administered to prevent activation and loss of thrombocytes, (G).

Hepatocellular carcinoma (HCC) is most sensitive and, perhaps not unrelated to its sensitivity, rich in arginase, an enzyme, which converts arginine to ornithine. First rounds of cancer cells dying within a tumor lesion will release arginase and cause a further local depletion of arginine, making it even more difficult for the remaining cells to survive - a snow-ball effect of a sort. Another aspect of this unusual sensitivity of HCC to arginine depletion is its reduced ability to substitute citrulline for arginine due to its generally low expression of argininosuccinate synthase, an enzyme required for conversion of citrulline into arginine. There is now solid evidence that arginine depletion is an effective treatment for HCC (S.A.Curley, et al., "Regression of Hepatocellular Cancer in a Patient Treated with Arginine Deiminase", Hepato- Gastroenterology 2003, 50:1208-1211). Arginine deiminase greatly increases systemic concentration of citrulline and even in the case of HCC, there will likely be a sub- population capable of converting citrulline to arginine and thus leading to resistance to further treatment. The advantage of the approach disclosed here, in addition to its relying on simple, common substances, is that not only arginine, but also ornithine and citrulline are suppressed and it thus offers a possibility of treating a wide range of cancers - current estimates suggest as many as eight in ten cancer types are susceptible to arginine depletion. Furthermore, our own in vitro work has suggested that deployment of IGF-I in arginine depleted state can eliminate even the most tenacious survivors of, in this case, a leukemia line.

Claims

1. A composition for the treatment of cancer comprising a lactate elevating composition.

2. The composition of claim 20 wherein the lactate elevating composition is selected from the group consisting of lactic acid, lactates, nitric oxide donors, vasoconstricting composistions, antibiotics, arginine free nutrition (amino acid mixtures contaning no arginine), and mixtures thereof.

3. The composition of claim 2 wherein the lactate elevating composition further comprises L-lactic acid.

4. The composition of claim 2 wherein the lactate elevating composition further comprises an L-lactate.

5. The composition of claim 4, wherein the L-lactate is selected from the group comprising potassium L-lactate ,calcium L-lactate, sodium L-lactate, magnesium L-lactate, and mixtures thereof.

6. The composition of claim 2 wherein the lactate elevating composition further comprises a nitric oxide donor selected from the group consisting of sodium nitroprusside, isosorbide dinitrate, and mixtures thereof.

7. The composition of claim 2 wherein the lactate elevating composition further comprises a vasoconstricting substances selected from the group consisting of vasopressin, vasopressin analogs, and mixtures thereof.

8. The composition of claim 2 wherein the lactate elevating composition comprises a mixture of lactic acid and lactates of either potassium, calcium, sodium or magnesium.

9. The composition of claim 8 wherein the lactic acid and the lactate are predominately of the L form.

10. The composition of claim 2, wherein the lactate elevating composition is adapted to be administered via the gastro-intestinal tract, i.e. per os or via a gastric feeding tube.

1 1. The composition of claim 2, wherein the lactate elevating composition is adapted to be administered via i.v. infusion.

12. A cancer treatment method comprising restricting arginine sources, particularly of endogenous production of arginine via intestinal-renal axis.

13. The cancer treatment method of claim 12 further comprising restriction of endogenous arginine source from protein turnover.

14. The cancer treatment method of claims 12 or 13 further comprising restriction of endogenous source of arginine from gut bacteria.

15. The cancer treatment method of claims 12, 13 or 14 further comprising restriction of exogenous souce of arginine from food.

16. The cancer treatment method of claims 12, 13, 14 or 15, whereby intestinal-renal axis is restricted by elevation of lactate.

17. The cancer treatment method of claim 16, whereby elevation of lactate is effected by delivery of lactate via gastro-intestinal tract, i.e. per os or via a gastric feeding tube.

18. The cancer treatment method of claim 16, whereby elevation of lactate is effected by delivery of lactate via i.v. infusion.

19. The cancer treatment method of claims 17 or 18, whereby lactate is delivered as a mixture of lactic acid and lactates of either potassium, calcium, sodium or magnesium.

20. The cancer treatment method of claims 17, 18 or 19 whereby the lactic acid and lactates are mostly of L form.

21. The cancer treatment method of claims 12, 13, 14 or 15, whereby intestinal-renal axis is restricted by PALO.

22. The cancer treatment method of claims 13, 14 or 15, whereby restriction of arginine source from protein turnover is effected by insulin.

23. The cancer treatment method of claim 22, whereby endogenous release of insulin is stimulated by elevation of blood glucose.

24. The cancer treatment method of claim 22, whereby insulin source is exogenous, injected i.v., i.m. or s.c.

25. The cancer treatment method of claims 13. 14 or 15, whereby restriction of arginine source from protein turnover is effected by insulin like growth factor one,

IGF-I.

26. The cancer treatment method of claims 13, 14 or 15, whereby restriction of arginine source from protein turnover is effected by insulin and insulin like growth factor one, IGF-I.

27. The cancer treatment method of claims 14 or 15, whereby restriction of endogenous source of arginine from gut bacteria is effected by antibiotics, preferably by those which are not absorbed, i.e. which do not cross into the blood circulation.

28. The cancer treatment method of claims 12, 13, 14 or 15, further comprising administering a nitric oxide donor during the period of low arginine, preferably percutaneously.

29. The cancer treatment method of claim 28, further comprising administering a vasoconstrictive substance, preferably vasopressin or one of its analogs.

30. The cancer treatment method of claims 28 or 29, whereby the patient is administered prostacycline or one of its analogs.

31. A cancer treatment method of claim 5, whereby elevation of lactate is effected by delivery of polylactic acid via gastro-intestinal tract, i.e. per os or via a gastric feeding tube.

32. A cancer treatment method of claim 31 , whereby polylactic acid molecular weight is in the range of 1000 to 3000 Dalton, preferably approximately 1500 Daltons.