Wednesday, February 22, 2012

Obesity and Cancer

In the laboratories of Doctor Vuk Stambolic at the University of Toronto in Canada, breast cancer cells are grown routinely utilizing a protocol that has been long established.  The nutrients that are required to sustain growth include a high concentration of glucose, Epidermal Growth Factor (EGF) and insulin.  If insulin is removed from the mix, the growth of the cells is slowed and eventually they die.  Interestingly, normal breast tissue cells from which the cancer cells were originally derived are insensitive to insulin; they lack insulin receptors on their cell surface that are required for cellular response to this factor.

Stambolic was so intrigued by this finding, that he has focused his research on the tumor-promoting effects of insulin.  There is present in healthy muscle, fat and liver cells a metabolic pathway (PI3) that is activated by insulin.    It is this pathway that is often mutated in human cancer cells.

It appears that insulin and an insulin-like growth factor (IGF) seem to play a critical role in accelerating the growth of a wide range of cancers.  Furthermore from an epidemiological perspective, the correlation between obesity and the occurrence of type 2 diabetes and cancer has been well established.  Obese and diabetic individuals have a far higher likelihood of getting cancer than their lean counterparts.  Excess body weight seems to be associated with between one-quarter to one-half of breast, colorectal and many other types of cancer. 

According to Michael Pollack – an oncologist at McGill University in Montreal, Canada – cancer "loves the metabolic environment of the obese person."  The paradigm that seems to be gaining support in regards to the mechanism behind this effect is that in the metabolic environment in the obese individual, especially in regards to increased levels of insulin and IGF, promotes and fosters the growth of incipient tumor cells as Stambolic noted in his breast cancer cell cultures.

This finding is of crucial importance, since there is an increasing proportion of the general population that is obese.