Cancerous Cells

i always had a keen interest in cancer inducing cells. Their ordinary and different nature.. what makes them different from other cells ? why is that they keep on dividing... so jst trying to study that....

Cancer refers to any one of a large number of diseases characterized by the development of abnormal cells i.e. cancerous cells, which divide uncontrollably and have the ability to infiltrate and destroy normal body tissue. It is an uncontrolled division of abnormal cells it means unrestricted divisions of cells.

Cancer cells are very similar to cells of the organism from which they originated and have similar (but not identical) DNA and RNA. This is the reason why they are not very often detected by the immune system. A cell has to pass through various stages of the cell cycle. These are the cells, which never enter in the G0 phase during the life cycle.
It is now known that a number of genes and their products are required in the cell cycle. A group of enzymes called protein kinases and other protein called cyclins, control progression of cells through the cell cycle. A mutation in the genes controlling these enzymes and protein could disrupt the cell cycle in such a way that control over the cell cycle is lost. This would lad to rapid proliferation of cells and hence cancer.

Cancerous (malignant) cells invade and damage surrounding tissue. Cancerous cells metastasize to distant parts of the body, causing secondary tumors. Metastasis describes when cancer spreads from the organ where it began to the different parts of the body. Initially cancer may move only to adjacent areas- into deeper layers of tissue or to nearby lymph nodes. Carcinomas spread to remote sites through the lymph system, the bloodstream, or other fluids. Generally cancer metastasizes in the Lymph Nodes, the Lungs, the Brain, the Bones or the Liver
Whereas normal cells have a limited lifespan controlled by the telomere gene, which signals the end of the cell line, cancer cells contain telomerase, an enzyme that alters the telomere gene and allows the cell to continue to divide. Cancer tissue, growing without limits, competes with normal tissue for nutrients, eventually killing normal cells by nutritional deprivation. Cancerous tissue can also cause secondary effects, in which the expanding malignant growth puts pressure on surrounding tissue or organs or the cancer cells metastasize and invade other organs.

ONCOGENES
Oncogenes are another category of genes, which regulate the cell cycle. Normally they function to promote cell division and are called proto- oncogenes. When they are expressed, these genes promote cell division. But if the proto-oncogenes become permanently switched on, or when certain viruses infect the cell and get integrated into the host genome as provirus. The provirus can switch on the proto-oncogenes such viruses are called tumorigenic viruses. then uncontrolled cell division will occur leading to tumour formation.

Proto-oncogenes are genes which promote cell growth and mitosis, a process of cell division, and tumor suppressor genes discourage cell growth, or temporarily halt cell division in order to carry out DNA repair. Typically, a series of several mutations to these genes are required before a normal cell transforms into a cancer cell. If these genes become permanently inactive or lost through mutations, the control over cell division is lost. Thus, such cells start poliferating in an uncontrolled fashion leading to cancer. Mutations in a tumor suppressor gene called p53 causing a range of cancers like breast, lung, bladder and colon cancer.

TUMORS

Some cells may arise, which do not respond to normal growth mechanism. These cells proliferate in an unregulated manner, and give rise to clones of cells that can expand to a considerable size, this growth is called tumour
Tumors can be benign or malignant:

Benign tumors are not cancer:
Benign tumors are rarely life threatening. Generally, benign tumors can be removed, and they usually do not grow back. Cells from benign tumors do not invade the tissues around them. Cells from benign tumors do not spread to other parts of the body.

Malignant tumors are cancer:
Malignant tumors are generally more serious than benign tumors. They may be life threatening. Malignant tumors often can be removed, but sometimes they grow back. Cells from malignant tumors can invade and damage nearby tissues and organs. Cells from malignant tumors can spread (metastasize) to other parts of the body. Cancer cells spread by breaking away from the original (primary) tumor and entering the bloodstream or lymphatic system. The cells can invade other organs, forming new tumors that damage these organs. The spread of cancer is called metastasis.

Cancer Cells in Culture
Both normal cells and cancer cells can be cultured in vitro in the laboratory. However, they behave quite differently.

Cancer cells may be immortal; that is, proliferate indefinitely in culture.

Normal cells pass through a limited number of cell divisions (70 is about the limit for cells harvested from young animals) before they decline in vigor and die. This is called replicative senescence. It may be caused by their inability to synthesize telomerase

Cancer cells show no contact inhibition. Once the surface of the dish is covered, the cells continue to divide, piling up into mounds.

Normal cells: when placed on a tissue culture dish, they proliferate until the surface of the dish is covered by a single layer of cells just touching each other. Then mitosis ceases. This phenomenon is called contact inhibition.

Cancer cells (and transformed cells) can usually grow on much simpler culture medium.

Normal cells are exceedingly fussy about the nutrients that must be supplied to them in their tissue culture medium.

Cancer cells almost always have an abnormal karyotype with
· abnormal numbers of chromosomes (polyploid or aneuploid)
chromosomes with abnormal structure:
translocations
deletions
duplications
inversions

Normal cells ordinarily have the normal set of chromosomes of the species; that is, have a normal karyotype.

Techniques being used for the treatment of cancer:
· Biologic Therapy
· Bone Marrow Transplants
· Chemotherapy
· Clinical Trials
· Complementary Medicine
· Gene Therapy
· General Treatment Concerns
· Hormone Therapy
· PDT Center
· Proton Therapy
· Radiation Oncology
· Surgical Oncology
· Targeted Therapies
· Vaccine Therapies