METHOD OF USING FETUIN TO INDUCE APOPTOSIS IN CANCER CELLS

Abstract: The present invention provides using fetuin to induce apoptosis in cancer cells. When properly prepared, fetuin is able to induce apoptosis in cancer cells, namely, leukemia cells, prostate cancer cells, colon cancer cells, breast cancer cells, and lung cancer cells.

Description: METHOD OF USING FETUIN TO INDUCE APOPTOSIS IN CANCER CELLS Inventors : David Tsai and Jenny Yu BACKGROUND OF THE INVENTION Human beings have had a long battle against cancer. Because the disease is so widespread, manifests itself in so many different ways and is so relentless, the potential market for effective cancer therapies is enormous. It is estimated that 10 million people in the U.S. either have or have had cancer. The National Cancer Institute (NCI) projects that in 1995, some 1.2 million new cases of cancer will be diagnosed in the United States, and that 538,000 people will die of the disease. Cancer is currently treated, with a low degree of success, with combinations of surgery, chemotherapy and radiation. The reason of the low degrees of success in cancer chemotherapy is as the following: Current chemotherapeutic approaches target rapidly dividing tumor cells. This approach is ineffective when the cancer is dormant or growing slowly. Such treatments also affect other, noncancerous cells that divide rapidly, causing harmful side effects. Only in the last several years has a new approach emerged in the battle against cancer. This approach is based on the newly discovered biological phenomenon called "Apoptosis". Apoptosis is also called "programmed cell death" or "cell suicide". (Krammer, et al . , "Apoptosis in the APO-1 System", Apoptosis: The molecular Basis of Cell Death, pp. 87-99 Cold Spring Harbor Laboratory Press, 1991) . In contrast to the cell death caused by cell injury, apoptosis is an active process of gene-directed, cellular self-destruction and that it serves a biologically meaningful function. (Kerr, J. F. R and J. Searle J. Pathol . 107:41, 1971) . One of the examples of the biologically meaningful functions of apoptosis is the morphogenesis of embryo. (Michaelson, J. Biol . Rev. 62:115, 1987). Just like the sculpturing of a sculpture, which needs the addition as well as removal of clay, the organ formation (Morphogenesis) of an embryo relies on cell growth (addition of clay) as well as cell death (removal of clay) . As a matter of fact, apoptosis plays a key role in the human body from the early stages of embryonic development through to the inevitable decline associated with old age. (Wyllie, A. H. Int. Rev. Cytol . 68:251, 1980) . The normal function of the immune, gastrointestinal and hematopoietic system relies on the normal function of apoptosis. When the normal function of apoptosis goes awry, the cause or the result can be one of a number of diseases, including: cancer, viral infections, auto-immune disease/allergies, neurodegeneration or cardiovascular diseases. Because of the versatility of apoptosis involved in human diseases, apoptosis is becoming a prominent buzzword in the pharmaceutical research field. Huge amounts of time and money are being spent in an attempt to understand how it works, how it can be encouraged or Inhibited and what this means for practical medicine. A handful of companies have been formed with the prime direction of turning work in this nascent field into marketable pharmaceutical products . The emergence of a core of innovative young companies combined with the tentative steps being taken by established industrial players are certain to make apoptosis research one of the fastest-growing and most promising areas of medical study of the 1990s. The idea that cancer may be caused by insufficient apoptosis merged only recently (Cope, F.O and Wille, J.j, "Apoptosis": The Molecular Basis of Cell Death, Cold Spring Harbor Laboratory Press, p. 61, 1991) . This idea however, opens a door for a new concept in cancer therapy Cancer cells may be killed by encouraging apoptosis. Apoptosis modulation, based on the processes present in normal development, is a potential mechanism for controlling the growth of tumor cells. Restoring apoptosis in tumor cells is an attractive approach because, at least in theory, it would teach the cells to commit suicide. Nevertheless, since the objective of cancer treatment is to kill cancer cells without killing the host, although apoptosis may open a new door for cancer therapy by inducing apoptosis in tumor cells, the success of this treatment is still dependent on the availability of drugs that can selectively induce apoptosis in tumor cells without affecting normal cells. In this patent application, we described the methods for the Isolation of proteins that specifically induce apoptosis in cancer cells without effect in normal cells. These proteins may present a new class of anticancer drugs that induce apoptosis in cancer cells which may offer a breakthrough in cancer therapy. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1. Incubation of LNCaP cells with control sample (PBS) fails to induce apoptosis; Fig. 2. Incubation of LNCaP cells with fetuin (25 μg/ml in PBS) show the characteristics of apoptosis, including condensation of the nucleus and fragmentation of DNA; Fig. 3. Incubation of HL-60 cells with control buffer (PBS) fails to induce apoptosis; Fig. 4. Incubation of HL-60 cells with fetuin causes apoptosis, with cells exhibiting condensation of the nucleus and fragmentation of DNA; Fig. 5. Fetuin prepared by the method described in section 4.A. at a concentration of 20 ng/ml induces apoptosis in tumor cells lines LNCaP, PC-3, HL-60, MCF-7, Colo 205, and Calu-1, while not inducing apoptosis in normal lung fibroblasts (CCD 39 Lu) ; Fig. 6. CCD 39 Lu cells incubated in control buffer (PBS) for 15 hours remained morphologically unchanged; Fig. 7. CCD 39 Lu cells incubated with Fetuin (25 μg/ml) for 15 hours remained morphologically unchanged; Fig. 8. MCF-7 breast cancer cells incubated in control buffer (PBS) remain unchanged; and Fig. 9. Fetuin at a concentration of 25 μg/ml induces apoptosis in breast cancer cells (MCF-7). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 1. Isolation of Bovine Fetuin' s Apoptotic Effect Thereof In Tumor Cell Lines (1) Fetuin is mainly a fetal protein, in the sense that the highest concentrations are found in serum and body fluids of embryos and fetuses. The concentration of fetuin in bovine serum drastically decreases, probably within a few days after birth, to 1-2% of the fetal level (Yang, et al . , Bioche . Biophy. Acta. 1130, 149-156 1992) (2) A histochemical study has shown that fetuin may control tissue remodelling and physiological cell death during embryonic development (Von Bulow, et al . , Histochemistry 99:13-22, 1993) . This result raised the possibility that fetuin may contain activity inducing cell death (apoptosis) . We therefore prepare/obtain fetuin and test in our apoptosis assay. Interestingly, we found that only bovine fetuin that is prepared by a special method is able to induce apoptosis in tumor cell lines. The commercial fetuin that is prepared by ammonium sulfate precipitation and EDTA treatment was found to contain very low activity in inducing apoptosis in tumor cells. A. Preparation Of Bovine Fetuin Bovine fetuin was prepared by the modified Spiro method (Spiro R. G. Journal of Biological Chemistry 235, 10: 2860, 1960) according to the following steps: 1. One hundred milliliters of Fetal Bovine Serum (FBS ) . 2. Add two hundred milliliters of 0.05 M Zinc Acetate containing 30% (V/V) ethanol, adjust to pH 6.4 by IM NH40H- NH4C1, let stand 15 hours at -5° C. 3. Collect the supernatant by centrifugation, add 1.0 M Barium Acetate and 95% ethanol to give 0.03 M Barium Acetate, 25% ethanol. Let stand 2 hours at - 5°C. 4. Collect the supernatant by centrifugation, add 95% ethanol to give 40% ethanol. Let stand 15 hours at -10 °C. 5. Collect the precipitate. Dissolve the pellet by Phosphate buffer saline. The purified fetuin showed a single protein band with apparent molecular weight of 63 Kd on SDS-PAGE. B. Induction Of Apoptosis In Tumor Cell Lines Using Bovine Fetuin Fetuin purified from fetal bovine serum by the procedure described above was dissolved in phosphate buffer saline (PBS) . The free Zinc Acetate and Barium Acetate were removed by repetitive concentration. Fetuin was tested in LNCaP and HL-60 cells. LNCaP or HL-60 (1,000 cells) was seeded 10 microliters RPMI containing 15% or 20% Fetal bovine serum, penicillin and streptomycin at 37 degree, 5% C02 in microtray plates (25 μl wells, Robbins Scientific Corp.). Fetuin (in 10 μl PBS) at concentration of 100 ng/ml was added 3-4 hours after cells were seeded. After incubation of the tested sample with cells for 15 hours, two microliters of Hoechst dye (0.03 ng/ml in PBS) was added. Two hours later, cells that were stained with Hoechst dye were examined under fluorescence microscope. The nuclei of apoptotic cells showed DNA condensation and fragmentation can be easily identified by Hoechst dye staining. The percentage of apoptotic cells was calculated by the following eςruation: % Apoptotic cells= Number of cells with DNA condensation and fragmentation Total cell number As shown in Fig. 1, the nuclei of the LNCaP cells that have been incubated with control sample (PBS) are normal and healthy. However, the nuclei of the LNCaP cells that have been incubated with fetuin (100 ng/ml in PBS) show the characteristics of apoptosis (Fig. 2) . First, the cells in the presence of fetuin showed the condensation of nucleus, demonstrated by the more intense fluorescent light compared with the control nucleus. Secondly, the nucleus condensation is accompanied by the fragmentation of DNA, demonstrated by the breakage of nucleus as shown in Fig. 2. As the nucleus condensation and DNA fragmentation are the two morphological characteristics of cells under apoptosis. These results suggest that fetuin contains an activity inducing apoptosis in LNCaP cells. As shown in Fig. 3, the nuclei of the HL-60 cells that have been incubated with control buffer (PBS) are normal and healthy. However, the nuclei of the HL-60 cells that have been incubated with fetuin show the characteristics of apoptosis (Fig. 4) . Fetuin causes the condensation of nucleus, demonstrated by the more intense fluorescent light compared with the control nucleus. Secondly, the nucleus condensation is accompanied by the fragmentation of DNA, demonstrated by the breakage of nucleus as shown in Fig. 4. As we have mentioned above, the nucleus condensation and DNA fragmentation are the two morphological characteristics of cells under apoptosis. These results suggest that fetuin contains an activity inducing apoptosis in HL-60 cells. C. Bovine Fetuin Selectively Induces Apoptosis In Cancer Without Having Effect On Normal Cell Lines We compared the effect of fetuin on the induction of apoptosis in various cell lines. As shown in Fig. 5, at concentration 50 μg/ml, fetuin prepared as described above strongly induced apoptosis in tumor cell lines such as: LNCaP (prostate cancer) , PC-3 (prostate cancer) , HL-60 (leukemia) , MCF-7 (breast cancer) , Colo 205 (colon cancer) , Calu-1 (lung cancer) . Normal lung fibroblast (CCD 39 Lu) on the other hand, is not affected by fetuin. Fetuin was found to be inactive in inducing apoptosis in CCD 39 Lu cells (normal lung fibroblast) at the concentration (25 μg/ml) that highly induced apoptosis in LNCaP (prostate cancer) or HL-60 cells (leukemia) . Fetuin (25 μg/ml) prepared as described above was incubated with CCD 39 Lu cells grown in MEM in microtray plate for 15 hours. As shown in Figs. 6 and 7, the CCD 39 Lu cells remained morphologically unchanged in the presence of fetuin (Fig. 7) . At this concentration (25 μg/ml) of fetuin, as shown in Fig. 9, in the presence of fetuin, less MCF-7 cell remaining, due to cell death and cell shrinkage, was observed (Fig. 9) D. Only Fetuin Prepared By The Method Described Above Is Able To Induce Apoptosis In Tumor Cell Lines We found that fetuin purchased from Sigma has very low activity in inducing apoptosis in LNCaP cells. However, fetuin (25 μg/ml) prepared in our laboratory by the method described above induces apoptosis in LNCaP cells by up to 90% in 4 hours. For the fetuin purchased from Sigma, apoptosis inducing activity was observed only at a very high concentration (>250 μg/ml) and at long incubation time (2 days) . We estimated that the activity of fetuin prepared in our laboratory is more than fifty thousand fold higher than that of fetuin prepared by other methods . We have examined the preparation method for Sigma' s fetuin and found that these fetuins are prepared by methods including ammonium sulfate precipitation and EDTA treatment. Both treatments may cause the deprivation of Zinc ion from the protein which may cause the irreversible loss of the protein activity.

Claims: We claim: 1. A method of inducing apoptosis in cancer cells by administering fetuin to said cancer cells. 2. A method of inducing apoptosis in cancer cells by administering fetuin to said cancer cells, wherein said cancer cells are prostate cancer cell, leukemia cells, breast cancer cells, colon cancer cells or lung cancer cells.

Inventors: TSAI DAVID, YU JENNY, TSAI, DAVID, YU, JENNY
Applicants: TSAI DAVID, YU JENNY, TSAI, DAVID, YU, JENNY
Application year: 1999
Main classification: A61K38
IPC codes: A61K38, C07K14