Why does the cancer return? Why is it transferred?

With the development of science, cancer treatments are constantly being updated, to some extent improving the survival rate of cancer patients. !----such as: surgical renewal, multidisciplinary care, improvement of chemotherapy drugs, the introduction of targeted biologics, and the emergence of "molecular-targeted drugs."Despite these great advances, many new anticancer drugs can reduce tumors, but their impact on the survival time of patients is very small, there are still a considerable number of patients after treatment will have cancer recurrence, and there are many incurable metastatic solid tumors, so the survival rate of patients with advanced solid tumors is still very low., most people have a question: Why does cancer return? Why is it transferred? In fact, many studies have found that most current treatments have cytotoxicity or cell inhibition effect on cancer cells, and most tumor cells die from exposure to chemotherapy, but a small number of cells survive chemotherapy and can cause cancer to return.What cells are in this part of the cell? Cancer, for example, is like a tree, and cancer treatment may simply eliminate branches and leaves on the ground, rather than the roots under the cancer ground, and over time, the roots underground will grow new cancers.scientists came up with a hypothesis - the cancer stem cell hypothesis, cancer stem cells are like the roots of cancer.before we talk about cancer stem cells, let's start with stem cells. the concept ofstem cells was introduced around 1900, but it was not until around 1960 that stem cells were actually discovered.two Canadian scientists observed visible nodules in the spleen of mice, described as "spleen colonies," and later confirmed that each nodule did come from the growth and development of individual cells, which are stem cells.normal stem cells have three characteristics: (1) they can self-renew; (2) they can differentiate into multiple lines, and (3) they can be balanced between self-renewal and differentiation, thereby strictly regulating the number of stem cells.So in a normal body organ, stem cells are the source of all cells in the organ, and because of these characteristics, stem cells can produce all the subcells in the organ and repopulate the organ after injury.today, stem cell research is a hot topic in scientific research.So what are cancer stem cells? As early as 1889, Steven Paget's groundbreaking paper first proposed the "seed and soil hypothesis" for cancer, which assumed that cancer cells in tumors had the inherent ability to "seed" distant organ metastasis.slowly, the scientific community has come up with a cancer stem cell hypothesis.cancer stem cell hypothesis suggests that some cells in tumors have stem cell-like properties.first compelling evidence of the existence of cancer stem cells came in 1997, when scientists Bonnet and Dick demonstrated that only CD34 (-) CD38 (-) cells from patients with acute myeloid leukemia (AML) can cause hematopoietic malignancies in immunodeficiency mice.later identified cancer stem cells in many solid tumors, including breast cancer, brain tumors, lung cancer, colon cancer, melanoma and so on. cancer stem cells are a small number of cells in tumors, also known as "tumor initiation cells." like normal stem cells, cancer stem cells have the ability to renew themselves and produce different offspring. they differ in that cancer stem cells are carcinogenic, and when they are transplanted into animals, tumors can form, while normal stem cells do not do that, and their offspring cells are abnormally differentiated and proliferate. the adverse effects of cancer stem cells are: (1) malignant tumors; (2) resistance to chemotherapy drugs for the treatment of malignant tumors, resulting in chemotherapy resistance, causing cancer to recur, and (3) causing distant metastasis of cancer. essentially, cancer stem cells maintain the vitality of tumor cells through self-renewal and infinite proliferation. the movement and migration of cancer stem cells makes the metastasis of tumor cells possible. cancer stem cells can sleep for long periods of time and have a variety of drug-resistant molecules that are not sensitive to the external physical and chemical factors that kill tumor cells. therefore, tumors tend to relapse some time after conventional treatments have eliminated most common tumor cells. eliminating tumor stem cells means cancer can be cured? In fact, cancer stem cells in the tumor tissue is very small, it is difficult to screen cancer stem cells in the body's tumor tissue. second, the surface markers of cancer stem cells identified by the experiment are still very limited, and even normal cells express these surface antigens, making it difficult to distinguish normal cells from cancer stem cells with targeted drugs. , the cancer stem cell microenvironment is similar to the common stem cell microenvironment, and cancer stem cells can be used in many ways to escape treatment. so it's hard to completely isolate cancer stem cells and eliminate them. but with the development of science, the research of cancer stem cells is more and more, the detection, separation and treatment of these cells are also moving to a new level. believes that as the future evolves, cancer stem cell therapy for solid tumors will become a reality. people may find and identify suitable clinical molecular targets, develop high-specific, highly sensitive cancer stem cell targets for the treatment of malignant tumors, and ultimately extend the patient's survival. 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