Archive for category Cancer
Understanding the Causes of Cancer
What Causes Cancer?
Most, if not all cancers are caused and perpetuated by a small population of tumor-initiating cells that exhibit numerous stem cell-like properties. Adult stem cells (SC) are involved in the regeneration and maintenance of our body tissues and account for one out of every 6 million cells. Each tissue has a unique population of specific SCs located in regions known as niches. In the SC niche, the SCs exist in a unique dormant state known as quiescence, and remain in this state until they are given the cues to be activated.
Activated stem cells go through two stages of development referred to as proliferation and differentiation. During proliferation, biochemical cues cause the cells to reproduce, resulting in an expanded population of similar cells. Differentiation puts a stop to proliferation with specific biochemical cues that cause the proliferating cells to differentiate into a specific type of cell. Once a stem cell has differentiated, it has a finite life span and is limited in how many times it can reproduce. The number of times a differentiated cell can reproduce is referred to as its Hayflick number.
Cancer results when a stem cell is stuck in proliferation, and is therefore not given the cues to differentiate. This situation results in a continually expanding population of undifferentiated cells that can not only exist anywhere in the body (metastasis), but also have unlimited life spans (no Hayflick number).
The biochemical cues for proliferation and differentiation are based on genes specific to each tissue type. In general, genes that initiate proliferation are called oncogenes while genes that initiate differentiation are called tumor suppressors. Cancer, therefore, could be seen as an over-activation of oncogenes accompanied by the inhibition of tumor suppressors. It is the ratio of oncogenes to tumor suppressors that determines the aggressiveness of the cancer.
Another key piece in the growth of cancers is a process called angiogenesis. Angiogenesis is the physiological process that tumors use in order to recruit new blood vessels in order to sustain their continual growth. They do this by over-expressing genes that initiate and direct the growth of new, leaky blood vessels from existing ones. Both angiogenesis and the spontaneous formation of new blood vessels (vasculogenesis) are initiated by unique combinations of genes. Read the rest of this entry »
HIV And Anal Cancer
Rectal (or anal) cancer is actually a fairly rare cancer. In fact, about 1 in 100,000 people have rectal cancer. However, this type of cancer is far more prevalent in men who have sex with men (MSM). The rate of occurrence rises considerably: to 70-144 in 100,000 people. Why does rectal cancer occur more often in men who have sex with men? When one looks at the facts, it actually makes sense. The average man who has sex with men that is also HIV positive is twice as likely to develop anal cancer as one who is HIV negative. What is it about HIV that increases the risk of men who have sex with men?
Let’s dig a little deeper. While HIV is one of many factors that increase the risk of anal cancer-including the same virus that causes genital warts-receptive anal sex is another factor. This is a common type of sexual intercourse among men who have sex with men, which is why MSM need to take additional precautions. Health professionals recommend that HIV-positive and other high-risk men be screened for anal cancer on a regular basis, including yearly exams and anal Pap smears. Rectal cancer is one of those cancers that are treatable if caught early.
A large percentage of anal cancer cases occur in people who have the human papillomavirus (HPV), the aforementioned virus that causes genital warts. Those who want to decrease the risk of developing anal cancer should also reduce their exposure to HPV; so that means they’ll have to take the necessary precautionary measures, such as using condoms for every sexual encounter. Also, experts definitely agree on having HIV-positive men who have sex with men take regular anal Pap smears. The smears detect the cell changes that are indicative of anal cancer, and early detection is vital in order to get treatment started quickly to keep the cancer from progressing. Read the rest of this entry »