Importance of knowledge of tumor biology

In previous blog posts, I discuss the importance of formal courses in tumor biology and nutrition for medical students, as well as for practicing physicians, especially oncologists.

We all know that pathogenic bacteria can develop resistance to specific antibiotics. I wonder whether the poor response to specific anti-tumor drugs in some cancer patients, and/or the development of remissions, are related to the ability of cancer cells to undergo heteroploid transformation and the specific selection of a karyotype.

I recall from my research as a cell biologist with the Department of Cancer Research at the University of Saskatchewan in Saskatoon (from 1961 to 1965) where I demonstrated that if a single cancer cell from a cell line was isolated and then allowed to undergo numerous cell divisions in cell culture – I used the tumor cell line called HeLa – that chromosomal analysis of many cells from this population showed cells with varying number of chromosomes. This phenomenon is called heteroploid transformation. Chromosomal values in my experiment ranged from the low 50’s to the 70’s, with a stem cell line in the early 60’s. (Hrushovetz, S.B. Importance of heteroploid transformation in the etiology of neoplasia. Proceedings of the 17th Western Regional Group MRC/NCI. 1963).

For my Master’s degree in Biochemistry from the University of Alberta, I had earlier shown that the addition of specific amino acids to the culture medium on which the cereal plant pathogen – called Helminthosporium sativum¬†– was sub-cultivated could alter the virulence of this pathogen in producing root rot disease. (see publication Phytopathology 47:261-264. 1957).

Alternatively, these experiments could be interpreted as demonstrating that for a pathogen to retain its virulence, it requires the presence of specific nutrients in its environment.

Cancer etiology: genetic or environmental

In order to prevent what is going to kill you, you need to know what those factors are. Let’s zero in on Canada’s number one killer: cancer.

Taking Canadian vital statistics on causes of death for the year 2011, there were 246,596 deaths. Statistics Canada divided the population into 4 age groups: 1-24, 25-44, 45-64, 65 years and over. The percentage of cancer deaths were 10%, 21%, 44% and 28% respectively.

Not surprisingly, cancer was the number one cause of death in all 4 age groups. But what surprised me was that cancer caused 10% of the 2,679 deaths in the youngest age group.

Most oncologists estimate that only 10-20% of cancers are genetically determined, with the rest due to environmental factors, with diet responsible for 35% and tobacco 25%(at least for males with the percentage in females rapidly approaching the same figure). It is also well-documented that the main reason for the higher cancer deaths in those 45 and over for lung cancer, and possibly also for the other environmental factors like diet and radiation, is due to the so-called lag period.

If this hypothesis for the mechanism of environmental carcinogenesis applies, then genetically-determined cancers in the 1-24 age group should be responsible for more cancer deaths with fewer from environmental such as by food, smoking, radiation, etc. Such information may give the oncologists, epidemiologists, and genetic counselling specialists new tools for their management of this major killer.