Colon cancer symptoms

Resource for Colon cancer symptoms and fun search portal . Continue for our current list for the Colon cancer symptoms

Love Poems, Love Calculator

Arts And Entertainment

Health And Fitness

Home Based Business

Self Improvement

Dating, Love, Sexuality

Relationships

Funny Pictures

MSN Nick Names,Display Pictures,Emoticons,Background

In cellular model systems, cells are exposed to carcinogenic influences (chemicals, radiation). In these systems, the first signs of a cell developing into a tumor cell are:

  • Immortality. The usual number of cell divisions for a mammalian cell is 50-60 (cell senescence), then it ceases to divide. Tumor cells keep dividing forever.
  • Altered morphology.
  • Building of cellular clusters (Foci).
  • Loss of contact inhibition.
  • Low or no need for growth factors.

Items 2-4 (above) can sometimes be traced to mutations in genes that result in a disruption of cell adhesion. Some cell adhesion proteins are oncogenes.

Cancer is, ultimately, a disease of genes. Typically, a series of several mutations is required before a cell becomes a cancer cell. We distinguish between oncogenes, which promote cancer when "switched on" by a mutation, and tumor suppressor genes, which prevent cancer unless "switched off" by a mutation. These mutations can have various causes: radiation or chemicals called carcinogens; some inherited predisposition is not uncommon; some viruses that can cause cancer have also been described. Usually, they carry in their genome some oncogene or tumor suppressor inactivating gene. In about 15% of all cancers, viruses seem to play a role; Bacteria, like Helicobacter pylori, also induce carcinogenesis by a process of chronic inflammation. Finally, damage by free radicals, which are a natural by-product of oxygen metabolism, can cause mutations in the DNA.

Malignant tumors such as carcinoma or sarcoma, lymphoma or leukemia originate from a cell or a group of cells in a multicellular organism that has several distinct properties:

  • evading apoptosis
  • Unlimited Growth Potential
  • self-sufficiency of growth factors
  • insensitivity to anti-growth factors
  • increased cell division rate
  • altered differentiation (specialization) ability
  • no ability for contact inhibition
  • ability to invade neighbouring tissue
  • ability to build metastases
  • ability to promote blood vessel growth (angiogenesis)