PHARMACEUllC INGREDIENT FOR MEDICAL TREATMENT AND PREVENTION OF CANCER
TECHNICAL FIELD
The present invention is generally related to pharmaceutical ingredients for treatment and prevention of cancer, and more particularly, a pharmaceutical preparation for treating and preventing cancer, comprising killed tumor cells and a material capable of inducing production of co-stimulatory molecules in antigen presenting cells and thus stimulating natural killer T cells.
PRIOR ART
Cancer is still a representative disease threatening the health and lives of humans, especially in industrialized countries, and as such is a major cause of death in humans. The exact cause of cancer remains unclear, but cancer is generally attributed to diverse factors, including internal factors such as genetic elements as well as external factors such as carcinogens, radiation, ultra violet, cosmic ray, chronic inflammation and injuries lasting for a long period of time, and oncogenic viruses. The potential involvement of genetic factors in cancer development is demonstrated in experimental animal models. However, there is insufficient knowledge of the role of genetic factors in induction of human cancer, except some cancers including retinoblastoma and familial adenomatous polyposis. Furthermore, it is not clear whether human cancer is caused by the genetic factors or environmental factors.
Cancer is not absolutely incurable, and moreover, can be fully overcome with aggressive treatment, especially when being found at an early stage. Therefore, it is important to detect cancer at an early stage, thus enhancing effectiveness of medical treatments. Also, even in case of
progressed cancer, if diverse and aggressive treatments are used, the fatal disease can be conquered, or patients' lives can be prolonged with reduced the pain. Further, it is most preferable that cancer progress is prevented. Therefore, there is an urgent need for development of therapeutic agents, such as vaccines to treat or prevent cancer. Cancer vaccines for effective prevention and treatment of cancer are generally developed based on immunotherapy.
Immune response is initiated by recognition of antigen by T cells. T cells recognize an antigen presented by antigen presenting cells (APC) such as dendritic cells or macrophages. In detail, after being processed, the antigen forms a complex with antigen presenting molecules such as major histocompatibility complex (MHC) on APC, and T cells recognize the antigen-MHC molecule complex through the antigen-specific receptor, which exists on T cells, thus activating T cells and consequently triggering immune response.
However, the immune system recognizes cancer cells as "self. Therefore, to obtain protective effects of cancer vaccines in cancer immunotheraphy, priority should be given to recognition of cancer cells as "non-self.
To achieve this goal, immunological tolerance/ignorance against self antigens presented by cancer cells should be overcome. Even though B cells or T cells recognizing specific antigens on cancer cells exist, they are typically killed, inhibited or inactivated as a result of immunological tolerance. Taking a detailed look at T cells, T cells are fully activated when recognizing antigens through T cell Receptor (TCR), as well as the co-stimulatory molecule, B7-1 or B7-2 molecule expressed on the surface of antigen presenting cells such as dendritic cells (DC) or macrophages, which act as a co-stimulatory signal. Upon recognizing only tumor-derived antigens with no recognition of the co-stimulating molecules, T cells are typically deleted, inhibited or inactivated. When cancer develops, typically, only tumor-specific antigens from tumor cells are produced, while the co-stimulatory molecules are not expressed, and immune cells capable of recognizing
and attacking the tumor cells are thus continuously removed or inactivated, resulting in the proliferation of the tumor cells with no of inteπuption of immune system. Therefore, in therapy and prevention of tumor, it is of essential importance for the immune system to recognize tumor- specific antigens simultaneously with recognition of the co-stimulatory molecules.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a pharmaceutical preparation for treating and preventing cancer, which can induce immune response against tumor cells by recognizing tumor cells as tumor-specific antigens, not "self, and augmenting expression of a co-stimulating molecule required for maximal T cell activation.
It is another object of the present invention to provide a pharmaceutical preparation for treating and preventing cancer using natural killer T cells (NKT cells) in order to increase expression of a co- stimulatory molecule to induce activation of T cells. To achieve the objects described above, in accordance with an aspect of the present invention, there is provided a pharmaceutical preparation for treating and preventing cancer, comprising a biologically effective amount of killed tumor cells, which act as antigens, and a biologically effective amount of a material to increase expression of a co-stimulatory molecule required for maximal T cell activation as an effective ingredient. In accordance with the present invention, the killed tumor cells are characterized by being dead by undergoing necrosis.
In accordance with the present invention, the co-stimulatory molecule is a B7-1 or B7-2 molecule. In accordance with the present invention, the material to increase expression of the B7-1 or B7-2 molecule as the co-stimulating molecule is characterized by having ability to stimulate NKT cells, which activate antigen presenting cells (APC) expressing the B7- 1 or B7-2 molecule.
In accordance with the present invention, the material to activate NKT cells is glycolipid or Hpid acting as a ligand for CD Id on APC that present antigen to NKT cells.
In accordance with the present invention, the glycolipid is alpha-galactosylceramide (alpha-
GalCer).
In accordance with the present invention, the material to activate NKT cells is an antibody selectively recognizing and activating NKT cells. i addition, in accordance with the present invention, the material to activate NKT cells is characterized by having ability to stimulate T-cell receptor (TCR) on NKT cells and thus activate
NKT cells.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a graph showing the effect of cancer vaccine prepared in Experimental Example 1 on viability of cancer-induced mice;
FIG.2 is a graph showing the effect of cancer vaccine over a prolonged period of time;
FIG. 3 shows an expression pattern of B7.2 molecule after stimulation of NKT cells by alpha- GalCer injection in mice;
FIG.4 is a graph showing pretreatment effect of alpha-GalCer at various times;
FIG. 5 is a graph in which viability of each group of Experimental Example 4 is plotted against time (days);
FIG. 6 is a graph in which viability of each group of Experimental Example 5 is plotted against time;
FIG. 7 is a photograph showing change in frequency of NKT cells in mouse liver at 16 hours after being treated with alpha-GalCer, which is one ingredient of an active vaccine of Experimental
Example 6;
FIG. 8 is a graph showing a result of a cytotoxicity test of spleen cells (effector cells) against male mice-derived cells (target cells), which are derived from female mice immunized with spleen cells from male mice, along with treatment with alpha-GalCer; and
FIG. 9 is a graph showing a result of a cytotoxicity test of spleen cells (effector cells) against live tumor cells (target cells), which are derived from female mice immunized with an active vaccine or an inactive vaccine according to the present invention.
BEST MODES FOR CARRYTNG OUT THE INVENTION
In accordance with an embodiment of the present invention, necrotic tumor cells function as antigens, alpha-GalCer, which is a potent activating ligand presented by CD Id acting as an antigen presenting molecule on APC that presents antigen NKT cells, is employed to increase production of a co-stimulatory molecule required for maximal T cell activation.
The CD Id molecule, which is a sort of antigen presenting molecule, belongs to group 2 of the
CD 1 d family, and exists in both humans and mice. Mouse CD 1 d molecule is mainly expressed in APC such as dendritic cells, B cells or macrophages (Brossay, L., et al. Mouse CD1 is mainly expressed on hemopoietic-derived cells. J. Immunol. 159:1216-1224 (1997); and Jessica H.
Roark, Se-Ho Park, Jayanthi Jayawardena, Uma Kavita, Mchele Shannon, and Albert Bendelac.
CD 1.1 expression by mouse antigen presenting cells and marginal zone B cells. J. Immunol.
160:3121-3127 (1998)).
Natural killer T cells (NKT cells), which is a novel T-cell lineage selected by the CD Id molecule, especially in mouse, semi-permanently express T cell Receptor (TCR), are activated by CD Id,
and express cell surface antigens similar to those on natural killer cells (NK cells). NKT cells are highly conserved in humans as well as mice, and represent 1-30 % of total T cells depending on tissues.
Lipid or glycolipid is predominantly considered to be a ligand for the CD Id molecule. It is reported that glycolipid phosphatidylinositol associates with CD 1 d (Joyce, S., et al. Natura ligand of mouse CDldl: cellular glycosylphosphatidylinositol. Science 279:1541-1544 (1998); and Gumperz, J. E., et al. Murine CD Id-restricted T cell recognition of cellular lipids. Immunity 12:211-221 (2000)), and glycolipid isolated from poriferans, alph-galactosylceramide (alpha- GalCer) also associates with CDld (Kawano, T, et al. CD Id-restricted and TCR mediated activation of Valphal4 NKT cells by glycosylceramides. Science 278:1626-1629 (1997); Benlagha, K, et al. In vivo identification of glycolipid antigen specific T cells using fluorescent CDld tetramers. J. Exp. Med. 191:1895-1903 (2000); and Spada, F.M., Koezuka, Y, and Porcelli, S. A. CD Id-restricted recognition of synthetic glycolipid antigens by human natural killer T cells. J. Exp. Med. 18.8:1529-1534 (1998)). Alpha-GalCer stimulates V alpha 14 TCR even in an infinitesimal amount in both humans and mice by associating with CD 1 d.
When the pharmaceutical preparation for treating and preventing cancer according to an embodiment of the present invention is administered to mice or humans, APC process necrotic tumor cells, and alpha-GalCer is presented by CDld to NKT cells, thus activating NKT cells. The activated NKT cells secrete a variety of cytokines including IL-4 and IFN-gamma (Bendelac, Albert, Mguel N. Rivera, Se-Ho Park, and Jessica H. Roark. Mouse CD 1 -specific NKl T cells. Development, Specificity, and Function. Annu. Rev. hnmunol. Vol. 15:535-562 (1997); and Yoshimoto, T, and Paul, W. E. CD4+NK1.1(+) T cells promptly produce IL-4 in response to in vivo challenge with anti-CD3. J. Exp. Med. 179:1285 (1994)), and these cytokines activate professional APCs such as macrophages or dendritic cells (DC), which present tumor antigens, as well as increase expression of the co-stimulatory molecules including B7-1 and B7-2
molecules, required for maximal T cell activation. T cells recognize antigens presented by CDld as well as the co-stimulatory molecule such as B7-2 through a receptor for CDld and CD 28 receptor for the co-stimulatory molecules. As described above, when the immune cells recognize tumor-specific antigens presented on APCs, the co-stimulatory molecules help to overcome immunological tolerance induced by tumors, with no deletion or inactivation of T cells, resulting in activation of T cells to memory T cells.
In addition, because of stimulating secretion of cytokines such as IL-4, IFN-gamma or IL-12, simultaneously with a series of activation of NKT cells, dendritic cells, B cells and T cells, the pharmaceutical preparation according to the present invention may be effective for therapy and prevention of infectious diseases and autoimmune diseases as well as cancer.
The pharmaceutical preparation according to the present invention can be used for diagnosis and therapy of cancer, as well as being utilized as a cancer vaccine with the aim of preventing cancer. In addition, the pharmaceutical preparation for treating and preventing cancer according to the present invention can be formulated into a solid, semi-solid or liquid form pharmaceutically suitable for oral or parenteral admrnistratiori, in combination with a pharmaceutically acceptable excipient, thus allowing oral or parenteral administration. The pharmaceutically acceptable excipient may be solid or Uquid, and includes one or more selected from materials capable of augmenting or regulating immune response. A unit dosage of the pharmaceutical preparation for treating and preventing cancer according to the present invention may vary depending on a patient's age and pathogenic state or pharmaceutical formulation thereof. The preferred unit dosage of the pharmaceutical preparation can be easily determined by those skilled in the art.
Necrotic tumor cells contained in the pharmaceutical preparation according to the present invention may vary depending on kinds of cancer or therapeutic purposes, and can be selected based on clinical data including kinds of cancer and developed states of cancer.
The present invention will be explained in more detail with reference to the following examples in conjunction with the accompanying drawings. However, the following examples are provided only to illustrate the present invention, and the present invention is not limited to them.
EXAMPLE
EXPERIMENTAL EXAMPLE 1
An effectiveness of a pharmaceutical preparation for treating and preventing cancer according to the present invention was evaluated in mice, as follows. 1. Preparation Step
An effect of the pharmaceutical preparation was investigated using C57BL/6 mice and a mouse melanoma cell line, B16, as well as alpha-galactoceramide (alpha-GalCer), KRN7000, to selectively activate NKT cells. To increase antigenicity of B16 melanoma used as tumor-derived antigens, the tumor cells were killed by necrosis, thus allowing their recognition by the immune system as if self tumor cells had been killed owing to invasion of phathogenens or injury. Necrotic cells more strongly stimulate the immune system than those killed by apoptosis (Gallucci S, Lolkema M, Matzinger P. Natural adjuvants: endogenous activators of dendritic cells. Nature Medicine 5(11): 1249-55 (1999)). When employing apoptotic cells, lower efficacy was found in comparison with using necrotic cells, which will be described in more detail in the below Examples.
When stimulating NKT cells, APCs such as macrophages or dendritic cells can be activated and expression of the co-stimulatory B7-2 moleucle can be thus increased, thereby enabling T cells to be activated by recognizing tumor-specific antigens presented by APCs and then recognizing and destroying tumor cells.
2. Preparation and use of a pharmaceutical preparation for treating and preventing cancer
B16 melanoma cells (obtained from Dr. Rosenberg's lab, NTH) were cultured in 10 % FBS- containing RPMI medium, and washed several times with PBS to completely remove medium. B16 cells were then prepared in lxlO7 cells/ml in PBS, and necrosis was induced by repeating four freezing (-70 °C) and thawing (37 °C) steps. Microscopic investigation showed no presence of cells having normal morphology. When being cultured again for over 2 weeks, no surviving cells were observed. To prepare a vaccine, the necrotic cancer cells were mixed with alpha-GalCer of 20 μg/ml in PBS (Kirin Beer Co., Ltd., Japan) in a volume ratio of 1:1 to give a vaccine comprising 5 M/ml of cancer cells and 10 μg/ml of alpha-GalCer, which was stored at - 70 °C until use (hereinafter, the vaccine is referred to as "active vaccine" or "active cancer vaccine"). As a control, another vaccine (hereinafter, referred to as "inactive vaccine" or "inactive cancer vaccine") was prepared by mixing the same amount of the necrotic tumor cells with PBS in a volume ratio of 1:1, and a solution composed of alpha-GalCer of 10 μg/ml (hereinafter, referred to as "alpha-GalCer"), not containing the necrotic tumor cells, was prepared.
3. Maintenance and immunization of mice
In order to evaluate effects of the active vaccine, 6-8 weeks aged C57BL/6 mice were immunized. All experiments were performed under the same environment using the same aged mice. To reduce experimental errors, mice of each group were maintained in the same cage, not isolated from each other. That is, one mouse of each of groups A to E was maintained in one cage, and about 10 such cages were further prepared, thereby minimizing potential errors in a specific cage. 2 weeks before injection of live tumor cells, mice were irnmunized. Group A was not immunized. Groups B, C and D were irnmunized by intraperitoneally injecting 0.1 ml of alpha-
GalCer, inactive vaccine and active vaccine, respectively. Group E was twice immunized by intraperitoneally injecting active vaccine 2 and 4 weeks before injection of live tumor cells. Thereafter, live tumor cells were injected intraperitoneally to mice of groups A to E, and growth rate of cancer and viability of mice were observed, in which the injection point was set as day 0. Mce having a distended abdomen owing to proliferation of cancer cells and remarkably reduced capacity of locomotion died a natural death, and mice obviously expected to die were killed by cervical dislocation.
4. Result FIG. 1 shows an effect of cancer vaccine on viability of cancer-induced mice. As shown in FIG. 1, after about 3 weeks, all mice of groups A to C were found to be dead. In contrast, when being administered with active vaccine, all mice except one mouse survived, while maintaining a healthy state, in which tumor cells were not found in their abdomen. Also, between groups D and E administered with the active vaccine once and twice, respectively, only a negligible difference was found. These results indicate that treatment with only tumor cells or alpha-GalCer has no effectiveness in therapy or prevention of cancer. Moreover, when repeatedly performing the experiment, mice treated with alpha-GalCer showed lower viability. However, when being injected with both the necrotic tumor cells and alpha-GalCer, the mice amazingly showed about 100 % viability, indicating that the immune system recognized the necrotic tumor cells as non-self antigens and thus induced immune response, in which alpha-GalCer plays an critical role, and the action of alpha-GalCer is accomplished in the presence of tumor antigens.
EXPERIMENTAL EXAMPLE 2
The long-term effect of the active vaccine as a candidate cancer vaccine was evaluated as follows.
1. Treatment with the active vaccine and injection with tumor cells
First, mice were treated with the active vaccine. After about 6 months, mice were injected with live tumor cells, in which mice were divided into group "non" not treated with any vaccine, group "d-150" treated with the active vaccine 5 months before tumor cell injection, and group "d- 14" treated with the active vaccine 2 weeks before tumor cell injection. All mice were maintained under same environment. The injection point of the active vaccine was set as day 0, and growth rate of tumor cells and viability of mice were evaluated according to the same method as in Experimental Example 1.
2. Result
FIG. 2 shows the long-term effect of the active vaccine. As shown in FIG. 2, it was found that proliferation of tumor cells is inhibited and tumor cells finally died in group "d-14" and group "d- 150" treated with the active vaccine 2 weeks and 5 months before tumor cell injection, respectively, but not in the group "non". These results indicate that the active vaccine according to the present invention is a potential cancer vaccine with long-term preventive effects, even with only one injection.
The efficacy as a cancer vaccine of the active vaccine, described in the Experimental Examples 1 and 2, originates from the result that NKT cells activated by alpha-GalCer give a signal to activate the immune cells, not to induce immunological tolerance, when DCs present killed tumor cells to the immune cells. This fact is supported by the finding in that alpha-GalCer does not activate DCs in NKT cell-deleted mice, while activating DCs in normal mice having NKT cells. FIG. 3 shows the presence of NKT cells and expression pattern of the co-stimulatory B7-2 molecule. After injecting alpha-GalCer to normal mice having NKT cells and CDl-/- mice
with deletion of NKT cells, activation of DCs was evaluated by investigating expression levels of B7-2 molecule. As shown in FIG. 3, B7-2 expression was increased in normal mice by injection of alpha-GalCer, whereas being unchanged in CDl-/- mice. This result indicates that the immune response against the necrotic tumor cells occurs by a mechanism in which alpha- GalCer activates NKT cells, and the activated NKT cells then activate DCs, thus leading to increased production of B7-2 molecule in DCs.
EXPERIMENTAL EXAMPLE 3
The following experiment was performed to identify whether alpha-GalCer shows antitumor immunity by a mechanism different with that of the necrotic tumor cells contained in the active vaccine.
1. Pretreatment of alpha-GalCer at various times After being preheated with alpha-GalCer (2 μg/mouse, i. v.) at various times, mice were injected with tumor cells, and the growth level of tumor cells was then investigated. lxlO6 tumor cells were suspended in 100 μl PBS to facilitate their transition to the liver and injected to the spleen using 30 gage syringes. Immediately after injection of tumor cells, a vein extended to the liver was tied up with a surgical silk thread (6-0 silk, Sherwood Medical, St. Louis, MO), and this surgical operation was carried out within about 5 rnin after anesmetizing mice with avertin (300 μl of 2.5 % Avertin/20g body weight, i. p.). 24 hours after the injection of tumor cells (day 1), mice were treated again with alpha-GalCer (2 μg/mouse, i. p.) to activate NKT cells and thus destroy tumor cells. 10 days after the injection of tumor cells (day 10), the liver was excised from each mouse, and transition of tumor cells was evaluated and liver weight was measured.
2. Result
FIG. 4 shows pretreatment effect of alpha-GalCer at various times, in which times at which pretreatment of alpha-GalCer was performed are given on the x-axis (for example, -2 hr means that alpha-GalCer was pretreated 2 hours before the injection of tumor cells, and -5 d means pretreatment 5 days before the injection of tumor cells), and weight of Hver (g/Hver) is given on the y-axis and increased according to transition and proHferation of tumor cells. As shown FIG. 4, in the group pretreated with PBS and then injected with tumor cells (rightmost), not treated with alpha-GalCer, the Hver was found to be heaviest among aU groups, indicating that proHferation of tumor ceUs is not inhibited. In the group pretreated with alpha-GalCer, injected with tumor ceUs and then not treated with alpha-GalCer, weight of Hver was found to have reduced. When being pretreated with PBS or alpha-GalCer 2 hours before the injection of tumor ceUs and treated with alpha-GalCer, mice showed reduced Hver weight. In the groups pretreated with alpha-GalCer once 5 days before, or twice, 10 days and 5 days before the injection of tumor ceUs, and treated with alpha-GalCer, weight of Hver was not found to decline. h other words, in the groups pretreated with alpha-GalCer once 5 days before, or twice, 5 and 10 days before the injection of tumor ceUs, and treated with alpha-GalCer, proHferation of tumor ceUs was not controUed effectively, in comparison with the groups pretreated with alpha-GalCer 2 days before or not, and moreover, when pretreatment was performed a longer time before, the control of tumor ceUs was more difficult. These results indicate that treatment with alpha-GalCer leads to increase in death rate of NKT cells, which is higher with the lapse of time, and reduction in abihty of NKT ceUs to directly attack tumor cells.
When being treated with alpha-GalCer, APCs are activated and then activate NKT ceUs, and the NKT cells secrete various cytokines. Some cytokines activate natural killer ceHs (NK cells) to produce killer molecules such as cytokine perform, other cytokines directly attack tumor cells. When being treated with alpha-GalCer once, regardless of being pretreated or treated after the
injection of tumor ceUs, the resulting powerful antitumor activity originates from the temporal effect of the action of alpha-GalCer. However, NKT cells activated by alpha-GalCer were kuled, resulting in the reduced abihty to directly destroy tumor ceUs. Therefore, these results demonstrate that alpha-GalCer alone has no efficacy as a cancer vaccine. Also, these results indicate that the temporal antitumor activity of alpha-GalCer is mediated by a mechanism completely different from the immune response induced by the necrotic tumor ceUs contained in the cancer vaccine according to the present invention, and that the activated NKT ceUs play a critical role in increasing titer of the necrotic tumor cells as antigens, and any material capable of activating NKT ceUs, such as alpha-GalCer, is useful in the cancer vaccine according to the present invention.
EXPERIMENTAL EXAMPLE 4
The foUowing experiment was carried out to identify whether the cancer vaccine according to the present invention can delete pre-existing tumor ceUs or not.
After dividing C57BL/6 mice into three groups, groups 1 and 2 were injected intraperitoneaUy with lxlO4 ceUs and lxlO5 ceUs of B 16 melanoma, respectively, and group 3 was injected intraperitoneaUy with lxlO5 cells of B 16 melanoma and then treated with the active cancer vaccine after aUowing 48 hours for tumor ceUs to be completely engrafted. Viability of mice was investigated according to time, and the result is given in FIG. 5. As shown in FIG. 5, viabiHty of the group 3 treated with the active cancer vaccine was remarkably improved in comparison with groups 1 and 2. This result demonstrates that the active cancer vaccine is effective in destroying the previously formed tumor cells, as weU as inhibiting incidence of tumors.
EXPERIMENTAL EXAMPLE 5
To identify whether the cancer vaccine according to the present invention shows antitumor activity through mediation by NKT cells and CDld, CD Id-deleted knock-out mice (CDld-/-) and normal young mice (Httermate, CD1D+/-), bom of the same mother as the knock-out mice, were treated with the active vaccine.
Group 1 was composed of CD Id-deleted mice (CDld-/-) treated with the active vaccine, group 2 was composed of normal mice (CD1D+/-) treated with the active vaccine, and group 3 was composed of treated with the inactive vaccine. 2 weeks after the treatment with the active or inactive vaccine, mice were injected with lxlO5 tumor cells. ViabiHty of mice was evaluated, and the results are given in FIG. 6.
As shown in FIG. 6, the group 1 (CDld-/-) with deletion of NKT cells was not improved in viability even though being treated with the active vaccine. Also, the group 3 (CD1D+/-) treated with the inactive vaccine, which was used as a control, did not show increased viabihty. Improved viabiHty was observed in the group 2 having NKT ceUs, treated with the active vaccine. This result indicates that the immune response against tumor ceUs, induced by the active vaccine, is dependent on action of NKT ceUs and CDld.
EXPERIMENTAL EXAMPLE 6
As demonstrated in the Experimental Example 5, the immune response against tumor cells, induced by the active cancer vaccine according to the present invention, is dependent on NKT ceUs. In this experiment, it was investigated whether the immune response is induced by direct action of NKT cells or not. Mice were treated with alpha-GalCer, which is one ingredient of the active cancer vaccine
according to the present invention. After 16 hours, the Hver was excised from mice, and change in numbers of NKT cells was evaluated. The results are given in FIG. 7 in which the upper and lower figures at the left side are results when being treated with a solvent and used as controls, and the right upper and lower figures are results when being treated with alpha-GalCer. Also, in FIG. 7, NK1.1 and CDl-Tetramer on the y-axis, and TCRab and CD5 on the x-axis represent antigens immunostained in the immune cells.
As shown in FIG. 7, when being treated with alpha-GalCer, NKT cells were activated rapidly and then entered the programmed cell death process, resulting in rapid reduction of NKT cells, indicating that NKT ceUs themselves do not directly attack tumor ceUs injected after 2 weeks.
EXPERIMENTAL EXAMPLE 7
The following experiment was performed to identify whether the antitumor activity of the active cancer vaccine results from acquired mimune response or not. C57BL/6 female mice were immunized through injection of spleen cells from C57BL/6 male mice, in which the immune response was induced in a specific manner for male spleen ceUs (male mice-specific antigens are called H-Y antigens), along with treatment with alpha-GalCer capable of stimulating NKT ceUs. A control was treated with only a solvent (vehicle). After 2 weeks, spleen cells were isolated from female mice. A cytotoxicity test was then carried out using the isolated spleen cells as effector ceUs to determine whether the spleen cells from female mice have cytotoxic activity against male mice-derived cells in vitro exposed to radiation for 5 days. The results are given in FIG. 8 in which the ratio of the effector cells (female mice- derived spleen ceUs, E) and the target ceUs (male mice-derived ceUs, T) is shown on the x-axis, and target-specific cytotoxic activity of spleen ceUs from female mice is shown on the y-axis. As shown in FIG. 8, the effector ceUs from female mice treated with alpha-GalCer were found to
have about 100 times higher cytotoxic activity than those from the control. For example, the E:T ratio showing 40 % target-specific cytotoxic activity was 100 in the control, while being only about 1 in the case of being treated with alpha-GalCer, indicating that in the case of being treated with alpha-GalCer, one effector cell has cytotoxic activity equivalent to 100 effector ceUs from the control. On the other hand, when using target cells from female mice, no cytotoxic activity was observed.
This result indicates that the cytotoxic activity against specific antigens can be increased remarkably when the specific antigens are injected together with activation of NKT cells. Moreover, when the antigens are tumor ceUs, the cytotoxic activity against tumor cells can also be remarkably enhanced, thus iUuminating the mechanism of the active cancer vaccine destroying or lling tumor ceUs.
EXPERIMENTAL EXAMPLE 8
With the same aim as in Experimental Example 7, this experiment was performed using tumor cells.
CDld+/- mice were treated with the active cancer vaccine or the inactive cancer vaccine (groups 1 and 2, respectively), and CDld-/- mice (group 3) were treated with the active cancer vaccine. After 2 weeks, spleen cells (effector ceUs) were isolated from each group, and in vitro activated with tumor ceU extract for 5 days. Cytotoxic activity of the effector ceUs against Hve tumor ceUs (target cells) was evaluated, and the results are given in FIG. 9.
As shown in FIG. 9, group 1 treated with the active cancer vaccine, in which NKT cells normally exist, showed remarkably increased cytotoxic activity against B 16 melanoma, and group 2 treated with the inactive cancer vaccine showed several tens times lower cytotoxic activity than that of group 1. On the other hand, when being treated with the active cancer vaccine, group 3
(NKT ceU-deleted CDld-/- mice), which was used as a control, was found to have weak cytotoxic activity.
These results indicate that the cytotoxic activity of the active cancer vaccine is obtained from increased cytotoxic reaction mediated by the activated NKT cells in a manner dependent on CDld. Therefore, the active cancer vaccine according to the present invention can be used for development of effective vaccines for cancer as weU as other diseases.
NKT cells can be activated through use of antibodies capable of selectively recognizing and activating NKT ceUs, and antibodies capable of stimulating T cell receptor (TCR) on NKT ceUs, as weU as alpha-GalCer.
The antibodies capable of stimulating NKT cells are weU known in the art. For example, anti- NK1.1 antibody interacting with NKl.1, which is a surface antigen of NKT ceUs, is theoreticaUy considered to have sufficient abihty to activate NKT cells. In addition, antibodies capable of recognizing NKT cell-specific T cell receptor (Val4Ja281) can be used. Taken together, when animals or humans are irnmunized with the cancer vaccine according to the present invention using the necrotic tumor cells as an antigen, simultaneously with activation of NKT cells, the immunological tolerance, leading to deletion of the immune ceUs capable of recognizing tumor cells, can be inhibited, the immune system can be increasingly activated by various signals, and memory T cells against tumor ceUs can be finaUy formed, thus making it possible to vaccinate against and treat cancer.
INDUSTRIAL APPLICABILITY
As described hereinbefore, when being immunized with the pharmaceutical preparation for preventing and heating cancer according to the present invention, the immune system can
recognize tumor ceUs as cancer-specific antigens, not "self, and increase production of the co- stimulatory molecules required for maximal T ceU activation, in which NKT ceUs can be activated by the material capable of stimulating NKT ceUs, contained in the pharmaceutical preparation, thus inducing the immune response against tumor ceUs. Therefore, the pharmaceutical preparation is very useful for prevention and therapy of cancer, with a potential use as a cancer vaccine.