Pathophysiology

Pathophysiology Study Guide

©2018 of 131 known as angiogenesis. Cancer cells can penetrate through four channels: blood vessels, lymphatic channels, body cavities, and transplantation by way of needles, surgical instruments, or diagnostic procedures. The metastatic tumors are highly fatal since most of the deaths caused by cancer and tumors are causedwhen the cancerous cells spread and impact distant organs. The rate of survival is higher when the tumors are localized. Moreover, metastasizing is one of the major features of malignant neoplasm cells. Tumor cells differ in their ability to spread. For instance, one of the tumor cells that rarely spreads is basal cell carcinoma. Different types of cancers are more disposed to metastasize from various primary tumors to specific organs. For instance, prostate cancer spreads to bones, colon cancer spreads to the liver, and stomach cancer is likely to metastasize to the ovaries. Mechanism of Oncogenesis Oncogenesis is the process by which normal cells are transformed into cancerous cells. It is also known as carcinogenesis. It is the process that includes a cytological, genetic, and cellular transformation of cells so that they undergo non-controllable division, resulting in malignant tumors. Viral Oncogenesis Oncogenic viruses lead to the proliferation of tumors from persistent virus infections. These viruses belong to different species of viruses including Hepadnaviridae, Flaviviridae, and Retroviridae. The viral oncogenes constitute both the DNA as well as RNA viruses. The DNA virus oncogenes encode the viral proteins, which helps the replication of a virus in the body, while the RNA virus oncogenes are responsible for altering the genes of the normal host cells in the body, which aids in virus replication. The cellular counterparts of the viral oncogenes (v-onc genes) are proto-oncogenes (c-onc genes), and they are responsible for the growth and development of cells. When these cells are activated by mutations, the cell grows in an uncontrollable manner. These genes are transformed into tumors through point mutations, chromosomal translocation, deletion, and amplification. These genes are categorized by their protein products like protein kinases, growth factors, growth factor receptors, and DNA binding proteins. Viral oncogenes mostly lead to the occurrence of hematopoietic tumors, sarcomas, and carcinomas. DNA tumor viruses exist in two forms of life: permissive and non-permissive cells. In permissive cells, viruses are responsible for causing cell lysis and death, while in non-permissive cells, the virus binds with different sites of the chromosomes. These viruses encode proteins like p53 and retinoblastoma and cause uncontrollable growth of cells. In contrast, all RNA tumor viruses are retroviruses. These viruses constitute three genes: gag, pol, and env, which synthesize the structural proteins, virion enzymes, and glycoproteins in cells. An extra gene, known as v-onc genes, is present in complex retroviruses that transform normal cells to malignant cells. There is another kind of gene known as tumor suppressor genes, or antioncigenes, which help prevent the transformation of normal cells to malignant cells. However, when the suppressive effects among these genes are lost, an uncontrollable growth of cells occurs. Cancer is mostly caused when these tumor suppressor genes lose in the struggle with the oncogenes. Achieve Page 17

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