Part 1. Tissue hypoxia: the prime cause of cancer (modern research)

A decade ago Dr. Rockwell from Yale University School of Medicine (USA) studied malignant changes at the cellular level and wrote, “The physiological effects of hypoxia and the associated micro environmental inadequacies increase mutation rates, select for cells deficient in normal pathways of programmed cell death, and contribute to the development of an increasingly invasive, metastatic phenotype” (Rockwell, 1997). The title of this publication is Oxygen delivery: implications for the biology and therapy of solid tumors.

Summarizing the results of numerous studies, a group of biological scientists from University of California (San Diego) chose the following title for their article, The hypoxia inducible factor-1 gene is required for embryogenesis and solid tumor formation (Ryan et al, 1998).

Under normal conditions, even a group of hypoxic cells dies (or is easily destroyed). What about cells in malignant tumours? Researchers from the Gray Laboratory Cancer Research Trust (Mount Vernon Hospital, Northwood, Middlesex, UK) concluded, “Cells undergo a variety of biological responses when placed in hypoxic conditions, including activation of signalling pathways that regulate proliferation, angiogenesis and death. Cancer cells have adapted these pathways, allowing tumours to survive and even grow under hypoxic conditions...” (Chaplin et al, 1986).

There is so much professional evidence about the fast growth of tumours when the condition of hypoxia is present that a large group of Californian researchers recently wrote a paper Hypoxia - inducible factor-1 is a positive factor in solid tumor growth (Ryan et al, 2000). Echoing their paper, a British oncologist Dr. Harris from the Weatherhill Institute of Molecular Medicine (Oxford) went further with the manuscript Hypoxia - a key regulatory factor in tumour growth (Harris, 2002).

When the solid tumour is large enough and the disease progresses, cancer starts to invade other tissues. This process is called metastasis. Does poor oxygenation influence it? “...Therefore, tissue hypoxia has been regarded as a central factor for tumor aggressiveness and metastasis” (Kunz & Ibrahim, 2003). That was the conclusion of a group of German researchers from the University of Rostock and the University of Leipzig.

Since dozens of medical and physiological studies yield the same result, what about the following title? Tumor oxygenation predicts for the likelihood of distant metastases in human soft tissue sarcoma (Brizel et al, 1996). This title claims that tumour oxygenation predicts chances of cancer invasion.

The reader can probably guess about the effect of cancer treatment and the chances of survival for those who suffer from severe chronic hyperventilation. Indeed, “... tumour hypoxia is associated with poor prognosis and resistance to radiation therapy” (Chaplin et al, 1986).

American scientists from Harvard Medical School noted “... Hypoxia may thus produce both treatment resistance and a growth advantage” (Schmaltz et al, 1998).

“Low tissue oxygen concentration has been shown to be important in the response of human tumors to radiation therapy, chemotherapy and other treatment modalities. Hypoxia is also known to be a prognostic indicator, as hypoxic human tumors are more biologically aggressive and are more likely to recur locally and metastasize” (Evans & Koch, 2003).

“Clinical evidence shows that tumor hypoxia is an independent prognostic indicator of poor patient outcome. Hypoxic tumors have altered physiologic processes, including increased regions of angiogenesis, increased local invasion, increased distant metastasis and altered apoptotic programs” (Denko et al, 2003).

The authors of one of the studies cited above mused about the origins of all these problems, “Surprisingly little is known, however, about the natural history of such hypoxic cells” (Chaplin et al, 1986). Why do they appear? What is the source of tissue hypoxia?

Conclusion. Appearance, development and metastasis of tumours are based on tissue hypoxia. Tumours are cries of the human organism for more oxygen.

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References for part 1

Brizel DM, Scully SP, Harrelson JM, Layfield LJ, Bean JM, Prosnitz LR, Dewhirst MW, Tumor oxygenation predicts for the likelihood of distant metastases in human soft tissue sarcoma, Cancer Reserach 1996, 56: p. 941-943.

Chaplin DJ, Durand RE, Olive PL, Acute hypoxia in tumors: implications for modifiers of radiation effects, International Journal of Radiation, Oncololgy, Biolpgy, Physics 1986 August; 12(8): p. 1279-1282.

Denko NC, Fontana LA, Hudson KM, Sutphin PD, Raychaudhuri S, Altman R, Giaccia AJ, Investigating hypoxic tumor physiology through gene expression patterns, Oncogene 2003 September 1; 22(37): p. 5907-5914.

Evans SM & Koch CJ, Prognostic significance of tumor oxygenation in humans, Cancer Letters 2003 May 30; 195(1): p. 1-16.

Harris AL, Hypoxia: a key regulatory factor in tumour growth, National Review in Cancer 2002 January; 2(1): p. 38-47.

Kunz M & Ibrahim SM, Molecular responses to hypoxia in tumor cells, Molecular Cancer 2003; 2: p. 23-31.

Rockwell S, Oxygen delivery: implications for the biology and therapy of solid tumors, Oncology Research 1997; 9(6-7): p. 383-390.

Ryan H, Lo J, Johnson RS, The hypoxia inducible factor-1 gene is required for embryogenesis and solid tumor formation, EMBO Journal 1998, 17: p. 3005-3015.

Ryan HE, Poloni M, McNulty W, Elson D, Gassmann M, Arbeit JM, Johnson RS, Hypoxia-inducible factor-1 is a positive factor in solid tumor growth, Cancer Res, August 1, 2000; 60(15): p. 4010 - 4015.

Schmaltz C, Hardenbergh PH, Wells A, Fisher DE, Regulation of proliferation-survival decisions during tumor cell hypoxia, Molecular and Cellular Biology 1998 May, 18(5): p. 2845-2854.

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© 2008 Artour Rakhimov (If you copy the content of these pages for educational purposes, please, indicate the site address and author's name).