Establishment Of A New Method For Tumor Chemosensitivity Test And Initial Study Of Its Application

Malignant tumor is a kind of disease with high incidence and mortality, which is hazardous to people's life and health. Researchers and clinicians have dedicated to scientific exploration and clinical practice in tumor treatment for a long time. Currently, cancer treatments mainly include surgery, radiotherapy, chemotherapy, endocrine therapy and immune therapy. Surgery, radiotherapy, chemotherapy are more widely used than others. Chemotherapy, as a systemic treatment which can kill tumor cells maximally in the patients'body, can increase patients'survival greatly, and is very important in cancer treatment.When the checkpoint lose of fuction, the defects of genes in the cells could not be recognized, which may lead to cell cycle disregulation and unlimited proliferation. The anticancer mechanisms of cytotoxic drugs are to interupt the tumor cell cycle and to induce tumor cell apoptosis, which depend on the normal function of checkpoints. However, as specific mechanisms and targets of anticancer drugs are different, the checkpoints remained in the tumors cells are also different, and tumor cells often show great histological and functional heterogeneity, for most kinds of malignant tumors, even the most effective chemotherapy drugs or strategies failed in some cases, leading to disease progression, relapse and metastasis. Therefore, it is important to choose appropriate chemotherapy strategy for every patient. In recent years, tumor chemosensitivity test have been conducted in clinical practice, making chemotherapy more individualized, which have increased the responds rates of the patients and improved the prognosis of the diseases. But there are still some shortcomings in the tumor chemosensitivity test methods which are widely used in our country. For example, all the methods need better techniques of primary cell culture, most are time consuming, cells may be contaminated during long time culture, and sometimes the tests show lower sensitivity, ect. All the shortcomings may interference the accuracy of the tumor chemosensitivity test, which makes the doctors not able to choose the best chemotherapy strategy, and the patient would not get the best effect after chemotherapy, all those restrict the promotion of the tumor chemosensitivity test.To solve the problems above, in this study, we explored a new tumor chemosensitivity test in vitro. Different cell populations in human body show different chemosensitivity, which is the principle of cancer chemotherapy. Not only the tumor tissues show higher proliferation index than normal human tissues, but also different proliferative potential exists in subpopulations within cancer tissues. The aim of chemotherapy is to destroy the proliferative populations within the tumor.First of all, because of what was mentioned above, when we examined the cytotoxic effect of the drugs to primary tumor cells from the patients, meanwhile, we also detected the proliferative potential of the same population. We suggest that the cytotoxic effect of the chemotherapeutic drugs should be measured by their ability to induce the proliferative populations to go to apoptosis. The primary tumor cells, after incubated with drugs for several hours, were stained with Annexin-V and PI, and then the apoptosis index was detected by a flow cytometer. The primary tumor cells from the same patient were also analyzed for Ki-67 expression. By the way, Ki-67 antigen was widely used as a proliferation marker. Statistical analysis of large samples showed that, the apoptosis and proliferation rates fluctuated in the same range, this phenomenon was in accordance with the theory of chemotherapy. So we suggested a new idea that the tumor chemosensitivity should be measured by the combined analysis of proliferation and apoptosis. Second, in order to validate the sensitivity and specificity of our newly established tumor chemosensitivity test in vitro, we used primary xenograft model in nude mice. After the mice being treated with different chemotherapeutic drug or their combinations, the results observed were compared with the results from in vitro tumor chemosensitivity tests. The results indicated that our newly proposed method of chemosensitivity test showed higher sensitivity and specificity than the traditional MTT test. Third, we chose some cases of patients with gastric or colorectal cancer, and they all received postoperative chemotherapy and were closely followed up. Patients were divided into drug sensitive and resistant group by our in vitro tumor chemosensitivity test. Drug sensitive group showed better prognosis than resistant group. This evidence also confirmed that our new tumor chemosensitivity test can reflect the drug chemosensitivity of primary tumor cells.Concerning the internal link of cell proliferation and apoptosis, after serial study, we established a new method of in vitro tumor chemosensitivity test, and the method were confirmed to be effective in animal models and clinical study, which provide a new approach to improve the effect of cancer chemotherapy.