ENZYMATIC METHOD FOR DETECTING CANCER IN MAMMALIAN TISSUE

Abstract: Improved method for assaying for cancer by detecting galactosyl transferase activity in cells wherein a marker specific for such activity is added to the cells and subsequently sensed.

Description: Description ENZYMATIC METHOD FOR DETECTING CANCER IN MAMMALIAN TISSUE Technical Field This invention is in the field of biochemistry. Background Art It has been shown that exfoliated bladder cells obtained from the urines of rats fed N- [4- (5-nitro-2- furyl) -2-thiazolyl] formamide for sufficient periods to produce bladder cancer contained significantly in¬ creased amounts of the enzyme galactosyl transferase. See Plotkin, G. M. , Brigham, S. C, Wolf, G. , Jacobs, J. B. and Arai, M. , "Uridine 5 '-diphosphate .galactose: glycoprotein galactosyl transferase activity in exfoliated bladder epithelial cells in rats fed N-i.4- (5-nitro-2-furyl) -2-thiazolyl] formamide", Cancer Bio- chem. Biophys., 1977, Vol. 2., pp 59-63. Exfoliated bladder cells obtained from rats similarly treated for much shorter periods of time which were insuffi- cient to cause bladder cancer did not show the sig¬ nificant increase in galactosyl transferase. Based upon this discovery that the level of a specific enzyme, galactosyl transferase, was signi¬ ficantly different in exfoliated cells from tissue containing cancerous cells than the level in compar¬ able cells from normal tissue, an enzymatic noninvasive test for cancer in mammalian tissue was developed. This test is described in U. S. Patent No. 4,132,600 ^issued to Plotkin et al. In the -method described therein, exfoliated cells from tissue to be tested and assayed for the level of galactosyl transferase activity are incubated with an exogenous galactose acceptor, such as a modified glycoprotein, and a galactose- containing substrate, such as a nucleotide galactose sugar. The amount of galactose transferred by the enzyme in a given time under standard conditions to the acceptor can then be determined and is a measure of the level of galactosyl transferase activity present. If the activity is significantly different from normal values, the organ is likely to contain cancerous tissue. The enzymatic noninvasive method for detecting cancer described in the Plotkin et al. patent has proven to be highly reliable. It would be an advantage, nevertheless, to have a more rapid, direct and/or in- expensive technique for detecting altered levels of galactosyl transferase. Disclosure of the Invention This invention relates to an improvement in the enzymatic noninvasive method for detecting cancer de- scribed in U. S. Patent No. 4,132,600. This improved method comprises directly sensing for a marker which is indicative of the amount of galactosyl transferase ac¬ tivity present on or within cells or which is shed therefrom. In one embodiment, the improved method comprises the addition, to cells being tested, of a marker which: (1) has a specific affinity for galactose or galactose residues; and (2) , once bound to galactose or galactose residues, can be detected because of its inherent opti- cal, electrical, magnetic, or other such properties or because it can be further reacted with materials having such detectable properties. Thus, a chemical assay is not required and a rapid and inexpensive technique for y^XJR O screening a large number of test cells which are poten¬ tially cancerous is provided. In the case of bladder cancer, it has been shown that the increased level of galactosyl transferase is predominantly associated with the plasma membrane. This was demonstrated by culturing cells of transitional cell carcinoma line MGH-Ul, in suspension, and then assay¬ ing them for galactosyl transferase by measurement of the transfer of I H]galactose from uridine diphosphate- I HJgalactose to desialylated ovine submaxillary mucin. The assay was optimized with respect to time and to pro¬ tein, uridine diphosphate-galactose, desialylated ovine submaxillary mucin, and Triton X-100 concentrations. This assay was then applied to fresh specimens of benign, inflamed, and neoplastic bladder epithelium from 33 patients who underwent cold-cup biopsies at cystoscopy. Transitional cell carcinoma specimens gave values in the range of 24.7-184.8 cp I H]galactose transferred/ug protein per hour (72.0 i 44.7, mean t S.D.M., n — 25); normal and inflamed specimens ranged from 0.8-46.1 cpm/ug protein per hour (8.3 ± 8.4, mean . S.D.M., n = 35) . By using a known method of cell rupture, cell ghosts, representing cell-surface membranes, were isolated both from the cultured cell line and from two biopsy specimens of transitional cell carcinoma, and the elevated galactosyl transferase was shown to be located in the cell-surface me brane fraction. Thus, the improved method of this invention can be employed to detect bladder cancer by assaying for an in¬ creased level of galactosyl transferase activity, or a product thereof, in the plasma membrane of bladder cells by introducing a marker compound which has a specific affinity for galactose moieties contained in the plasma membrane of such cells. The marker compound should also be capable of being easily sensed. A marker compound which has both properties can be formed by reacting the lectin Ricinus Communis Agglutinin 120 (RCA, 2Q ) , which is derived from Castor beans, with fluorescein, which is a fluorescent dye. This marker compound is commercially available pre-reacted and can be purchased, for example, from Vector Laboratories, Inc., Burlingame, California. Other lectins, in addition to RCA _ Q , can be em¬ ployed as long as they are specific for galactose or galactose residues. Lectins known to have such speci¬ ficity and which are commercially available include peanut agglutinin (PNA) , Phaseolus Vulgaris Erythro- Agglutinin (PHA-E) and Bandieraea Simplicifolia Lectin (BSL) . These lectins are also commercially available from Vector Laboratories. Of the above-mentioned lectins, RCA.,--, is the pre¬ ferred lectin because of the very .high specificity it displays for galactose or galactosyl residues. Similarly, other fluorescent dyes, in addition to fluorescein, can be employed. For example, all fluores¬ cent dyes in the Rhodamine family could be used in place of fluorescein. Further, the optically detectable marker need not be a fluorescent dye but might have an optical property, detectable in some other manner. For example, dyes which produce a direct stain which is detectable could also be bound to a lectin specific for galactose or galactosyl residues and employed with this invention. A wide variety of assays employing RCA - bound to fluorescein (RCA, 2 _-F) have actually been carried out. It has been found that this assay is highly re¬ liable and significant fluorescent in the plasma mem- brane.for all bladder cells known to be cancerous has been seen. On the other hand, no significant fluo¬ rescence has been detected for bladder cells known not to be cancerous . Evidence seems to suggest that it is a product caused by the increased presence of galactosyl trans¬ ferase in the plasma membrane which is being detected, al¬ though this evidence is not conclusive. There are other possibilities, and one is that it is simply the increased level of the enzyme itself which is being detected. In any event, there is a striking difference be¬ tween the fluorescence observed in the plasma membrane for cancerous bladder cells contrasted to the lack of any significant fluorescence in the plasma membrane of normal bladder cells. One of the major advantages of the method described herein is that there is currently existing apparatus cap¬ able of detecting optical properties, such as fluores¬ cence, employed with this method. For example, the Ortho Division of Johnson & Johnson produces a Cyto- fluorograph having this capability. Similarly, Becton & Dickinson markets a Fluorescence Activated Cell Sorter (FACS) and Coulter Systems markets a Cell Sorter, and both of these can be employed with this invention. Some of these, such as the Cytofluorograph, count the cells present in the sample by sensing scattered light from them while simultaneously counting the number of cells showing fluorescence. Typically, this data is obtained in a histogram which can be obtained in a very short time with a very small sample. As those skilled in the art will understand, the sensing technique employed to detect the marker compound need not be an optical technique. For example, it may be a ferromagnetic technique, such as nuclear magnetic resonance (NMRJ or electron spin resonance (ESR) em¬ ployed with a marker compound involving ferritin, which has ferromagnetic properties, and which is attached to a compound having a specific affinity for the enzyme. The marker may also be an enzymatic marker and may in¬ volve enzymes such as lacto-peroxidase or galactose- oxidase. Such enzymes oxidize galactose which can then be reacted with a chromogen to produce a color. Radiometric detection procedures are also suitable. For example, galactose in the plasma membrane of can ¬ cerous bladder cells could be first oxidized and then labeled with tritium which could be sensed by detect¬ ing the radioactive counts produced by a sample. Radioim unoassay (RIA) techniques can also be use d by employing an antibody coupled to a specific lectin in conjunction with labeled lecti-n. Although the experimental work described herein is directed to the detection of bladder cancer, it is believed that other forms of cancer can be detected in human or other mammals by the method disclosed. In addition, although the method described herein can usually be employed in a noninvasive mode, it is within the scope of this invention to employ this assay coupled with an invasive method for obtaining the test cells. Best Mode of Carrying Out the Invention This invention can be further and more specifically described by reference to the following examples. Example 1" Incubation of Marker Compound With Slices of Rat Tumor and Normal Bladder Tissue Frozen sections of tumor biopsies from cancerous rat bladder and normal rat bladder tissue were cut us¬ ing a cryotome. The cancerous tumor was produced by a FANFT-induced AY27 tumor cell line injected into a healthy rat. The biopsies were first frozen in liquid nitrogen or dry ice-acetone, placed in the cryotome and directly cut to 10 u slices. The need for paraffin imbedding was thus obviated. The tumor and normal slices were subsequently washed and submerged in a solution of RCA. ?n -F in phos¬ phate-buffered saline (PBS) for 10 minutes. The solu¬ tion of marker compound was prepared by dispersing 1 mg of RCA.. 2 n~ F obtained from Vector Laboratories in 10 ml of 0.002 M phosphate-buffered saline (PBS), pH 7.2. Slices were removed from the solution, washed once again and examined with a Leitz UV microscope. Striking fluorescence limited to the cell membrane was observed in the cancerous tissue whereas no fluo¬ rescence could be detected for the normal bladder tissue. . Example 2 Marker Compound Incubated With Rat Cell Lines Obtained From Bladder Tumor The cancerous rat cell line of Example 1 was em¬ ployed. Cells were maintained as monolayer cultures in 35 x 10 mm falcon plastic Petri dishes with McCoy's 5A medium modification supplemented with 10% fetal calf serum and incubated in 95% air/5% CO_ at 37° C. Cells were harvested near confluency by gentle trypsini- sation, washed, resuspended in 0.1 M MES, pH 6.5, and incubated. Glass cover slips (Fisher 22 x 22 mm thickness number 1) were placed in a humidified chamber and cells in media were placed on these slides. Cells grew as monolayers over the slides. After a confluent layer had formed over the slides, the slides were washed lightly in PBS in a humidified chamber in 0.5 ml of PBS containing RCA, ---F, prepared as in Example 1, was placed over the slide and incubated for 10 minutes at 30° C. After the 10-minute incubation at 30° C, the slides were washed gently, again with PBS, and examined with a Leitz UV microscope equipped with bandpass filters for fluorescein. Striking fluorescence limited to the cell membrane was observed. Example 3 Marker Compound Incubated With '•* Slices of Kidney and Ureter The procedures of Example 1- were employed except that the biopsies were taken from normal rat kidney and normal rat ureter. When the slices were examined with a Leitz UV microscope, no significant fluorescence could be detected. Example 4 Marker Compound Incubated With Human Cell Lines The procesures of Example 2 were used, except that four human transitional cell carcinoma cell lines established from human urinary bladder carcinoma at O the Massachusetts General Hospital were employed. These were MGH-Ul; MGH-U2; RT4; and T24. In addition, an established line derived from normal human urotheliam and the established line MGH-316 derived from normal skin fibroblasts were also employed. Strik¬ ing fluorescence, limited to the cell membrane, was observed in each tumor cell line, ' but no significant fluorescence was detected for the normal cell lines. Example 5 Marker Compound Incubated With Human Biopsies The procedures of Example 1 were employed except that frozen sections of twenty-one bladder tumor biop¬ sies and four normal urothelial biopsies were cut using a cryotome. Striking fluorescence, limited to the cell mem¬ brane, was observed-for the cancerous cells, but no significant fluorescence was detected for the normal biopsies . Example 6 Marker Compound Incubated With Human Urine Urine samples were collected from human patients with and without transitional cell carcinoma. The urine samples were kept at about 30° C and spun in a centrifuge at 1,000 x g. The pellets obtained were re- suspended in PBS and respun to wash the exfoliated cells. The cells thus obtained were resuspended in PBS, placed on a cover slip and processed with RCA, - jQ - as described in Example 2. Upon examination under the Leitz UV microscope, the same striking fluorescence, limited to the cell membrane, was observed for cells from patients having transitional cell carcinoma, but no significant fluorescence was detected for cells from the urine of normal patients. Example 7 Controls Glucose, galactose, lactose and concanavalin A lectin were each preincubated at 1, 10 and 100 mM with RCA-F solution described in Example 4. Examples 4, 5 and 6 were then repeated as described. Glucose had no effect on the results. Galactose and lactose (glucose-galactose) totally inhibited fluorescence at levels tested, presumably by binding to galactose sensitive to RCA lectin. Concanavalin A had no effect on binding of RCA, since it is a lectin specific for glucose and mannose. Industrial Applicability The method described herein is useful as a noninvasiv test for cancer in tissue from mammals, including humans. Equivalents Those skilled in the art will recognize, or be able to ascertain using no more than routine experimen¬ tation, many equivalents to the specific embodiments to the invention described herein Such equivalents are intended to be encompassed by the following claims. OM ■Λ, WIP

Claims: Claims 1. In a method for determining whether mammalian tissue cells are malignant by assaying cells from said tissue for a level of galactosyl transferase which is significantly altered com- 5 pared to the level in non-malignant cells: The improvement of adding to said cells a marker capable of being de¬ tected by a non-chemical technique, said marker having a specific affin- JL ity for galactose or galactose residues, and thereafter detecting the amount of said marker bound to said cells. 2. The improvement of Claim 1 wherein said marker com¬ prises a lectin coupled to a fluorescent dye. 5 3. The improvement of Claim 2 wherein said lectin comprises RCA, _ n . 4. The improvement of Claim 3 wherein said dye com¬ prises fluorescein. 5. An enzymatic noninvasive test for cancer in mammals, 0 comprising: a. incubating cells from said mammalian tissue in the presence of a marker which: (1) has a specific affinity for galactose or galactose residue moieties present in 5 the membrane of said cells; and, (2) is capable of being detected after it be¬ comes bound to said galactose or galactose residue moieties in said cell membrane; b. detecting the amount of said marker compound which is bound to said cell mem¬ brane; and, c. comparing the amount of said marker 5 compound with the cell membrane of test cells to the level which would be present in non-cancer cells. 6. A test of Claim 5 wherein said marker compound comprises a lectin bound to a dye. lϋ 7. A test of Claim 6 wherein said dye is a fluorescent dye. 8. A test of Claim 7 wherein said lectin comprises RCA 120. 9. A test of Claim 8 wherein said dye comprises 5 fluorescein. 10. A method for determining whether mammalian cells are cancerous comprising determining the level of galactosyl transferase in the plasma membrane of said cells and comparing the level found with the 0 level associated with non-cancerous cells. 11. A method of Claim 10 wherein said level of galac¬ tosyl transferase is determined by an optical technique _ 12. An assay for detecting galactosyl transferase on, 5 within or shed from cells comprising contacting said cells with a marker which (1) has a specific affinity for galactose moieties and (2) is capable O P of being sensed after it becomes bound to said moie¬ ties and thereafter sensing for said marker.

Inventors: PLOTKIN G, WOLF G
Applicants: MASSACHUSETTS INST TECHNOLOGY
Application year: 1980
Main classification: C12Q1
IPC codes: C12Q1, G01N33