AU2018246554B2

AU2018246554B2 - Diagnostic agent for cancer containing nematode mutant, and method for assessing tactic behavior using said mutant

Info

Publication number: AU2018246554B2
Application number: AU2018246554A
Authority: AU
Inventors: Takaaki HIROTSU
Original assignee: Hirotsu Bio Science Inc
Current assignee: Hirotsu Bio Science Inc
Priority date: 2017-03-31
Filing date: 2018-03-30
Publication date: 2021-03-11
Anticipated expiration: 2038-03-30
Also published as: WO2018181869A1; JPWO2018181869A1; CA3057970C; AU2018246554A1; JP6778449B2; CA3057970A1

Abstract

Provided are a diagnostic agent for cancer containing the nematode mutant AB1 strain, and a method for assessing migratory behavior using said mutant.

Description

Title of Invention: DIAGNOSTIC AGENT FOR CANCER CONTAINING

NEMATODE MUTANT, AND METHOD FOR ASSESSING TACTIC BEHAVIOR USING SAID MUTANT

Technical Field

[0001]

The present invention provides a diagnostic agent for cancer

that contains a nematode mutant and a method for assessing

tactic behavior using the nematode mutant.

Background Art

[0002]

A nematode exhibits attractive behavior toward cancer

patient's urine, and exhibits avoidance behavior toward healthy

subject's urine. Accordingly, it is possible to determine

whether a subject from whom urine is derived is a cancer patient

or a healthy subject based on tactic behavior of the nematode

(Patent Literature 1). More specifically, according to the

description in Patent Literature 1, a medium-scale study

involving 242 specimens was able to detect cancer patients with

a sensitivity of 100% and a specificity of 95%.

Citation List

Patent Literature

[0003]

Patent Literature 1: WO 2015/088039

Summary of Invention

[0004]

The present inventors have been working on the development

of a technique for identifying a healthy subject who gets a

false-positive result in the above described assessment based on

the tactic behavior. The present inventors found that a

nematode registered as an AB1 strain at Caenorhabditis Genetics

Center (CGC) at College of Biological Sciences at the University

of Minnesota in the United States was a nematode mutant and

usually exhibited avoidance behavior in a cancer patient and a

healthy subject but exhibited attractive behavior in some

healthy subjects. Furthermore, the AB1 strain exhibited

attractive behavior toward the urine of a healthy subject who

gets a false-positive result on a test using a wild strain. The

present invention is an invention based on these findings.

[0005]

Specifically, according to the present invention, the

following embodiments are provided.

(1) A composition including a nematode, for use in assessing

whether a subject suffers from cancer or not based on the tactic

behavior of the nematode toward urine of the subject, wherein

the nematode is an AB1 strain.

(2) The composition including a nematode, for use in assessing

whether a subject suffers from cancer or not based on tactic

behavior of the nematode toward urine of the subject, according

to the above described embodiment (1), wherein the nematodes are

a mixture of a wild-type strain and the AB1 strain.

(3) The composition according to the above described embodiment

(1), wherein the composition is used for urine toward which the

wild strain exhibited attractive behavior.

(4) The composition according to the above described embodiment

(3), wherein the composition is a composition for use in

detecting a false-positive subject.

(5) The composition according to the above described embodiment

(2), wherein at least one of the wild-type strain and the AB1

strain is labeled.

(6) A method for determining whether a subject suffers from

cancer or not, including

observing tactic behavior of an AB1 strain toward urine of

the subject, and

determining that the subject is or may be a healthy subject

when the AB1 strain exhibited attractive behavior toward urine

derived from the subject.

(7) A method for determining whether a subject suffers from

cancer or not, including

observing tactic behavior of a wild strain and an AB1 strain

of nematodes toward urine of the subject, and

determining that the subject does not or may not suffer from

cancer when the urine derived from the subject induced

attractive behavior of both the wild strain and the AB1 strain.

(8) The method according to the above described embodiment (7),

wherein the method further includes determining that the subject

does not or may not suffer from cancer when the urine derived

from the subject induced attractive behavior of both the wild

strain and the AB1 strain.

(9) The method according to the above described embodiment (8),

wherein the method further includes culturing a mixture of the

wild strain and the AB1 strain of nematodes.

(10) The method according to the above described embodiment (9),

wherein at least one of the wild-type strain and the AB1 strain

is labeled.

Brief Description of Drawings

[00061

[Figure 1] Figure 1 is a plan view of a petri dish 1 used for

assessing the behavior of a nematode as described in Example 1.

[Figure 2] Figure 2 is a graph showing taxis indexes of wild

strains and AB1 strains for urine of patients with various

cancers.

Detailed Description of the Invention

[0007]

As used herein, "subject" means a mammal such as a primate

(for example, a monkey, a chimpanzee, a gorilla, a bonobo, an

orangutan, a marmoset, and a human). For example, "subject"

means a human. Herein, the subject is preferably a human.

Herein, "subject" is used to include a healthy subject, a

subject suspected to suffer from cancer, and a subject suffering

from cancer.

[00081

As used herein, "cancer" means a malignant tumor. Cancers

may be broadly classified into three groups: a hematopoietic

tumor, an epithelial cancer (carcinoma), and a nonepithelial sarcoma (sarcoma). Examples of the hematopoietic tumor include leukemia, malignant lymphoma, and myeloma. Examples of the epithelial cancer include lung cancer, breast cancer, gastric cancer, large bowel cancer, uterine cancer, ovarian cancer, head and neck cancer, and tongue cancer. Examples of the sarcoma include osteosarcoma, chondrosarcoma, rhabdomyosarcoma, leiomyosarcoma, fibrosarcoma, liposarcoma, and angiosarcoma. As used herein, "cancer" includes early cancers such as a stage 0 early cancer and a stage 1 early cancer.

[00091

Herein, "a composition for use in diagnosing cancer" may be

simply referred to as "diagnostic agent for cancer."

[0010]

As used herein, "nematode" means Caenorhabditis elegans.

Nematode strains isolated from various environments have been

registered at and published by Caenorhabditis Genetics Center

(CGC) at College of Biological Sciences at the University of

Minnesota in the United States, and can be distributed thereby.

Accordingly, those of skill in the art can obtain most of known

strains from CGC. A hermaphrodite may be preferably used

because the hermaphrodite can propagate by self-fertilization.

[0011]

As used herein, "tactic behavior" means attractive behavior

or avoidance behavior. attractive behavior means behavior by

which a physical distance from a certain substance is reduced

and avoidance behavior means behavior by which a physical

distance from a certain substance is increased. A substance

that induces attractive behavior is referred to as an attractant and a substance that induces avoidance behavior is referred to as a repellant. It is a characteristic of a nematode that the nematode, based on olfaction, approaches the attractant and avoids the repellant. Behavior in which an organism approaches the attractant is referred to as attractive behavior (may be referred to herein as "positive") and behavior in which an organism avoids the repellant is referred to as avoidance behavior (may be referred to herein as "negative").

Furthermore, the attractive behavior and the avoidance behavior

are collectively referred to as tactic behavior.

[0012]

As used herein, "wild strain" means a wild strain of a

nematode and examples of the wild strain include an N2 Bristol

strain. The wild strain as used herein can be a strain that

exhibits attractive behavior toward the urine obtained from a

subject with cancer and exhibits avoidance behavior toward the

urine obtained from a subject without cancer.

[0013]

As used herein, "AB1 strain" refers to a nematode strain

registered at CGC as AB1 (registration number 5459) (see WBG 10

(2) 140-141 and WBG 8 (2) 52). The AB1 strain is believed to be

a nematode mutant separated from nature.

[0014]

The nematode exhibits attractive behavior toward cancer

patient's urine, and exhibits avoidance behavior toward healthy

subject's urine, as the present inventors already described in

W02015/088039. Accordingly, it is possible to determine whether

a subject is a cancer patient or a healthy subject based on tactic behavior of the nematode toward the urine obtained from the subject. However, more detailed examination of tactic behavior of the nematode has revealed that a certain percentage of healthy subjects may exhibit attractive behavior falsely

(hereinafter also referred to as "false-positive"). The present

inventors tested various nematode strains to detect a false

negative. Consequently, the present inventors succeeded in

isolating a strain that exhibits attractive behavior toward a

false-positive (AB1 strain).

[0015]

Method for Analyzing Urine Based on an Assessment System for

Tactic Behavior of Nematode

A method for analyzing urine based on an assessment system

for tactic behavior of a nematode can be performed by placing a

test sample (e.g., urine) obtained from a subject and a nematode

at a certain distance apart and observing whether the nematode

exhibits attractive behavior or avoidance behavior toward the

test sample. Then, when the wild strain exhibited attractive

behavior, it is possible to determine that the subject suffers

from or may suffer from cancer. In W02015/088039, a medium

scale study involving 242 specimens was performed in this way

and successfully detected cancer patients with a sensitivity of

100% and a specificity of 95%.

[0016]

More specifically, the method for analyzing urine based on

an assessment system for tactic behavior of a nematode may

include, for example, placing a test sample (e.g., urine) obtained from a subject on a petri dish (e.g., a petri dish containing a solid medium), placing a nematode at a certain distance apart from the test sample in the petri dish with the test sample placed thereon, allowing the nematode to move after the placement, and evaluating that the subject suffers from or may suffer from cancer when the nematode exhibited tactic behavior toward the test sample.

[0017]

The tactic behavior of the nematode can be assessed by using

a difference or a ratio between the number of nematodes that

approached the test sample and the number of nematodes that

avoided the test sample. In the assessment based on the

difference in the numbers of nematodes, when the difference is a

positive value, it is possible to determine that the test sample

induces attractive behavior in total and is derived from a

cancer patient; and when the difference is a negative value, it

is possible to determine that the test sample induces avoidance

behavior in total and is derived from a healthy subject. The

tactic behavior of the nematode can also be assessed for example

by using a taxis index as an indicator, as described below.

[Formula 1]

(Taxis index) = A -B A+B

wherein A is the number of nematodes that exhibited attractive

behavior toward the test sample, and B is the number of

nematodes that exhibited avoidance behavior toward the test

sample.

[00181

When the taxis index is a positive value, it is possible to

determine that the test sample induces attractive behavior in

total and is derived from a cancer patient; and when the taxis

index is a negative value, it is possible to determine that the

test sample induces avoidance behavior in total and is derived

from a healthy subject.

[0019]

The nematode may be labeled by a genetic modification

technique. Examples of the label include a fluorescent protein.

Nematodes that express a fluorescent protein emit fluorescence

of a specific wavelength when irradiated with excitation light

of a specific wavelength, and this allows for identification of

the individual nematodes. Examples of the fluorescent protein

include, but are not particularly limited to, green fluorescent

protein (GFP), yellow fluorescent protein (YFP), blue

fluorescent protein (CFP), and GCaMP.

[0020]

AB1 strain

The AB1 strain of the nematode exhibits avoidance behavior

toward the cancer patient and the healthy subject, unlike the

wild strain. However, the AB1 strain exhibits attractive

behavior toward some of the healthy subjects. The urines toward

which the AB1 strain exhibited attractive behavior were urines

derived from a subject diagnosed as a healthy subject for

example by a medical doctor. Therefore, a subject who was

positive in the assessment using the AB1 strain is likely to be

a healthy subject.

Accordingly, in the present invention, the AB1 strain can be

used in assessing whether a subject suffers from cancer or not

based on tactic behavior of the AB1 strain toward urine of the

subject. In this aspect, the present invention provides a

composition including a nematode, for use in assessing whether a

subject suffers from cancer or not based on tactic behavior of

the nematode toward urine of the subject, wherein the nematode

is an AB1 strain. In other words, the present invention

provides a composition including an AB1 strain, for use in

detecting a healthy subject in cancer diagnosis.

[0021]

The subject who was positive in the assessment using the AB1

strain was also positive in the assessment using a normal wild

strain, and this subject was a false-positive subject. Thus,

the subject who is positive in the assessment using the AB1

strain and is positive in the assessment using the normal wild

strain is likely to be false-positive.

Accordingly, in the present invention, the AB1 strain can be

used in assessing whether a subject who is positive in the

assessment using the wild strain is false-positive or not. In

this aspect, the present invention provides a composition

including a nematode, for use in assessing whether a subject

suffers from cancer or not based on tactic behavior of the

nematode toward urine of the subject, wherein the nematodes are

a mixture of a wild-type strain and an AB1 strain. The present

invention also provides a composition including a nematode, for

use in assessing whether a subject suffers from cancer or not

based on tactic behavior of the nematode toward urine of the subject, wherein the nematode is an AB1 strain and the subject is a subject in which urine of the patient induced attractive behavior in the assessment using a wild strain of the nematode.

[0022]

Method for Assessing Tactic Behavior toward Urine by Using AB1

Strain (1)

In the present invention, tactic behavior toward urine can

be assessed by using the AB1 strain, for example as described

below.

[0023]

The AB1 strain exhibits attractive behavior toward urine of

some healthy subjects. Accordingly, the AB1 strain can be used

in detecting the healthy subject's urine. The assessment method

can be performed, for example as described below.

First, the tactic behavior of the AB1 strain toward urine of

the subject (that is, urine obtained from the subject) is

observed. The urine toward which the AB1 strain exhibited

attractive behavior is or may be urine obtained from a healthy

subject. Accordingly, it is possible to determine (or assess,

expect, speculate, or diagnose) that a subject is or may be a

healthy subject when the AB1 strain exhibited attractive

behavior toward the urine derived from the subject. Thus, it is

shown that a subject is or may be a healthy subject when the AB1

strain exhibited attractive behavior toward the urine derived

from the subject.

[0024]

Method for Assessing Tactic Behavior toward Urine by Using AB1

Strain (2)

In the present invention, the AB1 strain shows positive in

subjects who were false-positive in the assessment test of

tactic behavior using other wild strains of nematodes; and shows

negative in other subjects. Accordingly, the AB1 strain can be

used in detecting a subject who is or may be false-positive from

subjects who were positive in the assessment of tactic behavior

using other wild strains of nematodes. The assessment method

can be performed according to, for example, an assessment method

(A) or an assessment method (B) as described below.

[0025]

Assessment Method (A)

First, the tactic behavior of the wild strain toward urine

of the subject (that is, urine obtained from the subject) is

observed. The urine toward which the wild strain exhibited

attractive behavior (that is, "positive" urine) is likely to be

urine obtained from a cancer patient. Then, the tactic behavior

of the AB1 strain toward the above described positive urine is

observed. The urine toward which the AB1 strain exhibited

attractive behavior is or may be urine obtained from a healthy

subject. Accordingly, it is possible to determine (or assess,

expect, speculate, or diagnose) that a subject is or may be

false-positive when the AB1 strain exhibited attractive behavior

toward the urine derived from the subject. Thus, it is shown

that a subject is or may be a healthy subject when the AB1

strain exhibited attractive behavior toward the urine derived

from the subject.

[0026]

Assessment Method (B)

In the above described assessment method (A), the wild-type

nematode (wild strain) and the AB1 strain were used separately

in the tests. In the assessment method (B), the wild strain and

the AB1 strain are mixed and used.

The wild strain and the AB1 strain can be cultured

separately. When the wild strain and the AB1 strain are

cultured separately, they can be mixed and used when the

behavior thereof is assessed. The wild strain and the AB1

strain can be mixed and used, without particular limitations, at

a quantitative ratio of 2:1 to 1:2, and preferably at a

quantitative ratio of about 1:1. The wild strain and the AB1

strain can also be cultured, without particular limitations,

under an identical condition.

The wild strain and the AB1 strain can also be mixed

together and cultured. For coculture, the wild strain and the

AB1 strain can be mixed at the time of culture and cultured

together. The wild strain and the AB1 strain can be mixed and

cultured, without particular limitations, at a quantitative

ratio of 2:1 to 1:2, and preferably at a quantitative ratio of

about 1:1. The growth speed of the AB1 strain is almost the

same as that of the wild strain, and thus, when the AB1 strain

and the wild strain are mixed at a ratio of 1:1 at the beginning

of culture, the quantitative ratio of nematodes obtained after

culture may be about 1:1.

The AB1 strain can be marked by a label. For example, a

visualizable label, for example a fluorescent label, and more

preferably a fluorescent protein label can be used as a label,

without particular limitations. A fluorescent protein can be stably expressed in a nematode by the genetic modification technique. In an aspect of the present invention, an AB1 strain that expresses a fluorescent protein is provided.

Alternatively, the wild strain can be marked by a label. For

example, a visualizable label, for example a fluorescent label,

and more preferably a fluorescent protein label can be used as a

label, without particular limitations. A fluorescent protein

can be stably expressed in a nematode by the genetic

modification technique. The label can be introduced into one or

both of the wild strain and the AB1 strain. When both of the

wild strain and the AB1 strain are labeled, the wild strain and

the AB1 strain may be labeled distinguishably.

Then, urine of a subject and the nematode mixture thus

obtained can be used to observe the tactic behavior.

Consequently, it is possible to determine (or assess, expect,

speculate, or diagnose) that a subject does not or may not

suffer from cancer when the urine derived from the subject

induced attractive behavior of both the wild strain and the AB1

strain. Thus, it is shown that a subject does not or may not

suffer from cancer when the AB1 strain exhibited attractive

behavior toward the urine derived from the subject.

The above described assessment method (B) may further

include determining (or assessing, expecting, speculating, or

diagnosing) that a subject suffers from or is likely to suffer

from cancer when the urine derived from the subject induced

attractive behavior of the wild strain and induced avoidance

behavior of the AB1 strain. Furthermore, the above described

assessment method (B) may further include determining (or assessing, expecting, speculating, or diagnosing) that a subject is or is likely to be a healthy subject when the urine derived from the subject induced avoidance behavior of both the wild strain and the AB1 strain. Thus, it is shown that a subject is or may be a healthy subject when the AB1 strain exhibited attractive behavior toward the urine derived from the subject.

[0027]

The composition including the AB1 strain of the present

invention can be used in the above described method for

assessing tactic behavior toward urine by using the AB1 strain.

[0028]

The present invention provides a method for preventing

and/or treating cancer, the method including administering an

anticancer agent to a subject who was determined to suffer from

or be likely to suffer from cancer by the above described method

of the present invention. In this embodiment, the method for

preventing and/or treating cancer may further include

determining that a subject suffers from or is likely to suffer

from cancer when the AB1 strain exhibited attractive behavior

toward the urine derived from the subject.

[0029]

The present invention is described below with reference to

Examples.

Example

[0030]

Example 1. Study of Tactic Behavior Based on Olfaction Using a

Plurality of Different Nematode Strains

In this Example, a plurality of different strains isolated

from various soils were used to assess tactic behavior thereof

based on olfaction.

[0031]

The nematode strain was purchased from Caenorhabditis

Genetics Center (CGC) and the tactic behavior of the nematode

based on olfaction was assessed. Specifically, culture of

nematodes was performed using a NGM plate described in Table 1

below.

[0032]

[Table 1]

Table 1. NGM plate NaCl 3 g/L

Bacto peptone 2.5 g/L

Agar 17 g/L

Cholesterol (5 mg/ml, in ethanol) 1 ml/L

KPO 4 (pH 6.0) 25 ml/L

CaCl 2 1 ml/L

MgSO 4 1 ml/L

[0033]

Assessment of the tactic behavior of the nematode was

performed by using an assay plate (a petri dish with a diameter

of 5 cm or 9 cm) described in Table 2 below.

[0034]

[Table 2]

Table 2. Assay plate (a petri dish with a diameter of 5 cm or 9

cm)

Bacto agar 20 g/L

KPO 4 (1 M) 5 ml/L

CaC1 2 (1 M) 1 ml/L

MgSO 4 (1 M) 1 ml/L

[00351

Urine samples of patients with various cancers were used as

an odor-producing substance. More specifically, each of the

urine specimens of patients with breast cancer, gastric cancer,

bile duct cancer, large bowel cancer, a cecum, prostate cancer,

pancreas cancer, or lung cancer and healthy subjects (including

false-positive healthy subjects) was diluted 10 times or 100

times and used.

[00361

The nematodes were cultured individually for four days at

200C. Figure 1 shows the plate used in the Example. The above

described odor-producing substance was spread on an area 5 for

placing the sample on the plate and the nematodes were placed on

an area 3 for placing the nematode on the plate, as shown in

Figure 1. Then, the behavior of the nematodes were observed at

230C.

[0037]

30 minutes after placing the nematodes, nematodes that

existed in a region 2 and a region 4 were counted and a taxis

index was calculated by using the following formula.

Taxis Index = {N (2) - N (4)}/{N (2) + N (4)} wherein N (2) is the number of nematodes that existed in the region 2 in Figure 1, and N (4)is the number of nematodes that existed in the region 4 in Figure 1.

[00381

Consequently, the normal wild strain of the nematode

exhibited an approaching and moving-toward behavior toward

cancer patient's urine and exhibited an avoiding and moving-away

behavior toward healthy subject's urine. However, the present

inventors discovered a strain that exhibited avoidance behavior

toward both of the cancer patient's urine and the healthy

subject's urine, among the nematode strains. The strain was an

AB1 strain. The AB1 strain is a strain that was isolated and

registered at CGC in 1984, and is available from CGC.

[00391

It was found from further assessment of the behavior of the

AB1 strain that the AB1 strain exhibited attractive behavior

toward false-positive healthy subject's urine toward which other

wild strains exhibited attractive behavior by mistake.

[0040]

This result revealed that the AB1 strain was a mutant that

behaved differently from the wild strains in terms of attractive

behavior based on olfaction.

It can be understood that this result also indicates that

urine toward which the normal wild strain exhibits attractive

behavior and the AB1 strain exhibits avoidance behavior is

positive, and urine toward which both the normal wild strain and

the AB1 strain exhibit attractive behavior is false-positive.

[0041]

Then, the AB1 strain was fluorescently labeled.

Specifically, green fluorescent protein (GFP) was expressed in

the body wall muscle of an AB1 strain to generate the AB1 strain

that emits fluorescence when irradiated with excitation light.

Specifically, a plasmid that contains a gene including a GFP

gene operably linked downstream to myo-3 promoter was injected

into the gonad of the AB1 strain to obtain a transformant. This

strain was irradiated with y ray to integrate the injected

plasmid into the chromosome.

[0042]

Then, an equal number of imagoes of the labeled AB1 strain

and imagoes of the wild strain were plated on an agar culture

medium sprinkled with feeds, and a mixture including the labeled

AB1 strain and the wild strain was obtained after 3 to 5 days.

After confirming that each strain accounts for about half, these

strains were used for the assessment of tactic behavior. In the

assessment of behavior, the nematodes were observed under

irradiation of visible light and excitation light for GFP and

each taxis index could be calculated. The result is shown in

Figure 2.

[0043]

As is shown in Figure 2, the normal wild strain (N2 Bristol

strain in Figure 2) has a positive taxis index for cancer

patient's urine and exhibits attractive behavior theretoward;

and has a negative taxis index for healthy subject's urine and

exhibits avoidance behavior theretoward. In contrast to this,

it was revealed that the AB1 strain had a negative taxis index

for both the cancer patient's urine and the healthy subject's urine and exhibited avoidance behavior theretoward.

Furthermore, eight different wild strains other than the N2

Bristol strain were tested and all the strains exhibited tactic

behavior similar to that of the N2 Bristol strain.

[00441

As described above, use of the AB1 strain and the normal

wild strain allows for reducing the percentage of false

positives, and improvement in accuracy of assessment can be

expected.

Claims

The claims defining the invention are as follows:

1. A composition comprising a nematode, when used to assess

whether a subject suffers from cancer or not based on tactic

behavior of the nematode toward urine of the subject, wherein

the nematode is an AB1 strain.

2. The composition when used according to claim 1, wherein the

nematodes are a mixture of a wild-type strain and the AB1

strain.

3. The composition when used according to claim 1, wherein the

composition is used with urine which attracts the wild strain.

4. The composition according to claim 3, when used to detect a

false-positive subject.

5. The composition according to claim 2, wherein the wild-type

strain and/or the AB1 strain is/are labelled.

6. A method for determining whether or not a subject suffers

from cancer, comprising:

observing tactic behavior of a wild-type strain of nematode

and an AB1 strain of nematode towards urine of the subject; and

determining that the subject does not or may not suffer from

cancer if the urine derived from the subject attracts both the

wild strain and the AB1 strain.

7. A method for determining whether or not a subject suffers

from cancer, comprising:

observing tactic behavior of a wild-type strain of nematode

and an AB1 strain of nematode towards urine of the subject; and

determining that the subject does not or may not suffer from

cancer if both the wild-type strain and the AB1 strain avoid the

urine of the subject.

8 A method for determining whether or not a subject suffers

from cancer, comprising:

observing tactic behavior of a wild-type strain of nematode

and an AB1 strain of nematode towards urine of the subject; and

determining that the subject suffers from cancer if the

wild-type strain is attracted to the urine of the subject and

the AB1 strain avoids the urine sample of the subject.

9. The method according to any one of claims 6 to 8, wherein

the method further comprises culturing a mixture comprising the

wild-type strain of nematode and the AB1 strain of nematode.

10. The method according to claim 9, wherein the wild-type

strain and/or the AB1 strain is/are labelled.

Abstract

Provided are a diagnostic agent for cancer containing a

nematode mutant, an AB1 strain, and a method for assessing

tactic behavior thereof using the nematode mutant.