basicbiology2.blogspot.com CANCER Cancer is the one of the most dreaded diseases of human being and is a major cause of death all over the glove. more than a million indians suffer from cancer and a large number of them die from it annually. the mechanisms that underlie development of cancer or oncogenic transformation of cells, its treatment and control have been some of the most intense area or research in biology and medicine.
Uncontroled, Abnormal and excessive mitotic division of cells is called cancer (carb = cancer).
study of cancer is called oncology.
this abnormal and undifferentiated cells are called cancerous cells.
Normal cell division regulation by proto-oncogenes and it is suppressed by tumour surppressor gene.
Uncontroled, Abnormal and excessive mitotic division of cells is called cancer (carb = cancer).
study of cancer is called oncology.
this abnormal and undifferentiated cells are called cancerous cells.
Type of tumours-
- Benign tumour : capsulated, localised to the site of origin & does not spread to another parts of body , it is non metastatic, non -malignant , non-cancerous , non invasive eg. bone tumour - Osteoma muscle tumour - Myoma lymph node tumour - lymphoma
- Malignant tumour (malignant = marmful): some of the cancerous cells detach from their origin place and spread to other parts of body by blood and lymph. now the cancerous cells from fresh coloies there. this is called metastasis or sec.grouth. this type of tumour is called metastatic or cancerous tumour. it is invasive tumour. e.g. All malignant tumour are called cancer
In our body , cell growth and differentiation is highly controlled and regulated . In cancer cells, there is breakdown of these regulatory mechanisms. normal cells show a property called contact inhibition by virtue of which contact and other cells inhibits their uncontrolled growth. cancer cell to have lost his property. as a result of this, cancerous cells just continue to divide giving rise to masses of cells called tumors.
tumors are of two types : benign and malignant.
benign tumors normally remain confined to their original location and do not spread to other parts of the body and cause little damage.
The malignant tumors, on the other hand are a mass of proliferating cells called neoplastic or tumor cells. these cells grow very rapidly, invading and damaging the surrounding normal tissues. as these cells actively divide and grow they also starve the normal cells by competing for vital nutreients. cells sloughed from such tumors reach distant site through blood, and wherever they get lodged into he body, they start a new tumor there. this property called metastasis is the most feared property of malignant tumors.
CANCER IS DIVIDED INTO 3 CLASSES ON THE BASIS OF ORIGIN
(1) Carcinoma : This tumour originated from the skin and epithelial tissue eg:
(a) brain carcinoma (b) oral carcinoma
(c) gastric carcinoma (d) colon carcinoma
(e) lung carcinoma (f) cervical carcinoma
(g) Adeno carcinoma (gland tumour) (h) breast carcinoma
carcinoma is most common type of tumour (85%)
➽ Breast cancer in female and prostate cancer in males are common incidence in world. lung cancer accounts for 31.1% of all cancer death in men and 25% in women.
➽ cervical (uterine cervix) cancer in females and oral cancer in male are common in india.
melanoma - it is type of carcinomas. these are cancerous growths of melanocytes (a type of skin cells).
(2) SARCOMA : this is tumour of mesodermal tissue (1%). eg.
bone cancer - Osteosarcoma
muscle cancer - myosarcoma
Lymph node cancer - Lymphosarcoma
(3) Leukaemia (leucocyte = W.B.C.) or blood cancer : This is cancer of white blood cells (WBC).
(a) chronic myelogenous leukaemia (CML): This fatal cancer occurs mainly due to reciprocal translocation between chromosome-22 (philadelphia chromosome) and chromosome 9.
(b) Burkitt's lymphoma: this is type of leukaemia which is produced due to reciprocal translocation between chromosome-8 and chromosome-14.
According to a rough estimate about 8 lakhs cases of cancer are detected in india every year out of which 4 lakhs succumb to death.
Normal mechanism of body growth:-
Normal cell division regulation by proto-oncogenes and it is suppressed by tumour surppressor gene.
Chemical or physical agents that can Couse cancer are known as carcinogen. Depending on their mode of action, carcinogen fall into the following main categories :
(a) Agents that can cause alterations in the genetic material (DNA), resulting in oncogenic transformation.
(b) Agents that promote the proliferation of cells, which have already undergoes genetic alterations responsible for oncogenic transformation. These agents are called tumour promoter e.g. some growth factor are hormones.
(c) Cancer causing DNA and RNA viruses (tumour viruses) have been shown to be associated with oncogenic transformation.
Transformation of a normal cell into cancer cells if the registration is upset
Cancer cell do not show contact inhibition phenomenon which is shown by normal cells (when normal cells contact with other cells they inhabit uncontrolled growth by activation of tumour suppressor gene of cells).
CAUSE OF CANCER
Transformation of normal cells into cancerous neoplastic cells may be induced by physical, chemical or biological agents. These agents are called carcinogens. lonising radiations like X-rays and gamma rays and nonionizing radiations like UV cause DNA damage leading to neoplastic transformation. The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer. Cancer causing viruses called oncogenic viruses have genes called viral oneogenes. Furthermore, several genes called cellular oncogenes (C-onc) or proto oncogenes have been identified in normal cells which, when activated under certain conditions, could lead to oncogenic transformation of the cells.
CARCINOGENS
causative agent cancer- Carcinogen
(a) chemical factor : tobacco and betel chewing cause oral cancer. Heavy smoking (N-Nitrosodimethylene) couse oral cancer cancer of larynx and lungs. combustion product of coal and pesticides, artificial flavour, sweetner, synthetic food, add flavour, hormonal imbalance in body cause cancer.
Hormonal imbalance or oestrogen access cause breast cancer.
Urinary bladder cancer is common in dye workers.
(b) physical factors ; sharp teeth cow's tongue cancer Kashmiri people keep Kangri close to a skin that cause skin cancer and this a skin cancer is called Kangri cancer.
(c) radiation factor Cosmic Rays, X-rays and UV rays cause cancer. there are five time more incidence of leukaemia in Hiroshima and Nagasaki due to radiation effect of nuclear bombing.
(d) biological factor : oncogene (cancer producing gene) and oncovirus cause cancer (HIV and AIDS).
CANCER DETECTION AND DIAGNOSIS
Early detection of Cancer is essential as it allow the disease to be treated successfully in many cases.
Flowing are the technique for cancer detection and diagnosis
(1) Blood examination : this is the test for increase cell count in the case of leukaemia detection of the Tumor Marker like Alpha fetoprotein in blood is done. Alpha fetoprotein increased during liver cancer.
(2) Biopsy : a piece of the suspected tissue is cut into thin section, stained and is examined under microscope. This is generally histopathological study by pathologist ( cancerous cells have a very high value of karyoplasmic index).
(3) F.N.A.C. : (fine needle aspiration cytology) - eg. Breast cyst / tumour.
(4) X-ray, C-T Scan and M.R.I : this technique are very useful to detect cancer of the internal organ.
In C.T. scane x-ray are used to generate a three-dimensional image of the internal of an object.
In MRI be used as strong magnetic field and non ionizing radiation to secretly detect pathological and physiological changes in the living tissue.
(5) pap smear : it is used for Cervical carcinoma and detect cytological character of cancer.
(6) Modern technique : these involve the detection of the molecular changes that occurs in Cancer cells; which enable and early diagnosis of cancer. Monoclonal antibodies against cancel a specific antigene are coupled to appropriate radioisotopes. These antibodies are then used for detection of cancer.
TREATMENT OF CANCER
flowing are the methods :
(a) surgery : by removing the entire cancerous tissue and infected lymph node.
(b) radiotherapy : tumor cell are indicated lethally taking proper care of the normal cell and tissue surrounding the tumor mass. Cobalt therapy (Co-60), 1-131, X-ray radiation are given. these radiation destroyed the rapidly dividing cells.
(c) chemotherapy : several chemotherapeutic drugs used to kill the cancerous cells. Many anticancerous drugs are used. these are
> Vincristine (weed - cantharanthus roseus = Vinca rosea)
> Vinblastine (weed - Cantharanthus roseus = Vinca rosea)
majority of drugs have side effect like hair loss anemia etc
Taxol - Obtained from (taxis Baccarat) inhabit the DNA synthesis in cell cycle of cancerous cell but these drugs so many serious side effects.
(d) Immuno therapy : one of the recent approach of cancer treatment involves augmentation of natural anticancer immunological defence mechanism. Monoclonal antibodies have been used to various ways. research is in progress to develop cancer vaccines.
most of Cancer are treated by combination therapy of surgery, radiation, and anticancer drugs. (e) tumor cell have been shown to avoid detection and destruction by immune system. Therefore the patients are given substance called biological response modifiers such as Alpha interferon which activate there immune system and help in destroyed in the tumor.
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