Brother, it iz well established that when physical & mechanical forces are kept on cells for long time, cells secrete some unknown molecules, that directly or indirectly cause cancer.In 2011 a paper was published by Natasha case in Journal of Biological Chemistry 286, 39450-39456, Sep28 2011

whereby she tried to see whether the mechanical strain could phosporylate the akt.

But lots are yet to found.

It may also go the other way round...

There was quite a bit of excitement in the news recently about this story:

G. Venugopalan et al. Externally applied forces can phenotypically revert malignant breast epithelial structures. American Society for Cell Biology meeting, December 17, 2012, San Francisco.

Terry fox believed his osteosarcoma was a result of the car accident he had 1 year before being diagnosed.

There are working theories that say mechanical forces contribute to cancer through processes like genomic instability. Some very tangible proofs exist in literature as well. But these mechanical forces are in the order of nano-/pico- or even femto- newton scales that act on the genome, proteins, etc within the cell. For example, any receptor on cell surface can generate force up on activation (like phosphorylation) which can be further sensed by sensor proteins downstream and can be passed on to the nucleus where it affects gene expression patterns (can be mechano-chemical or purely mechanical as well). Of course, these forces pass from one cell to another cell and then there is hierarchy of force flow along tissue which we are beginning to understand slowly.

Also, mechanical forces from blood flow, blood vessel walls, etc., are involved in the metastasis of tumor. These are only very little things that we know so far.

Some References here:

1. Lavelle, C. DNA torsional stress propagates through chromatin fiber and participates in transcriptional regulation. Nat Struct Mol Biol 15, 123-5 (2008).

2. Michor, F., Liphardt, J., Ferrari, M. & Widom, J. What does physics have to do with cancer? Nat Rev Cancer 11, 657-70 (2011).

3. Wang, N., Tytell, J. D. & Ingber, D. E. Mechanotransduction at a distance: mechanically coupling the extracellular matrix with the nucleus. Nat. Rev. Mol. Cell Biol. 10, 75-82 (2009).

4. Fudenberg, G., Getz, G., Meyerson, M. & Mirny, L. A. High order chromatin architecture shapes the landscape of chromosomal alterations in cancer. Nat. Biotechnol. 29, 1109-1113 (2012).

Check out the work from Valerie Weaver and Minna Bissel groups, for example:

Paszek, M, and Weaver VM. The tension mounts: mechanics meets morphogenesis and malignancy. J Mammary Gland Biol Neoplasia. 9:325-42, 2004.

Well what about chronic irritation resulting in chronic inflammation and vice versa and the resultant dys-regulation of mechanical forces. Look at the oral or lip cancer due to cigar or cigarette or hooka or pipe smoking, Kangri cancer in Kashmir, horn cancer in bullocks due ploughing, saddle related cancer in horses, cancers caused by several parasites in animals and people, all do have some mechanical irritation fragment as a role to play, apart from other hypotheses. To add, heard of bed sores resulting in squamous cell carcinoma.

As it is well established, mechanical forces lead to morphogenetic changes to cells in prior to birth period. Also as cancer cells are body cells in different forms and morphogenetic parameters, mechanical forces can introduce cancer as well as correcting the pathological conditions leading to malfunction of the cells.

The Wikipedia article on carcinogenesis

http://en.wikipedia.org/wiki/Carcinogenesis

provides a quite complete introduction to the subject--

EXCEPT there is no mention of the role of mechanical (force, deformation) in stimulation of tumorogenesis or carcinogenesis. Anyone can edit a Wikipedia article. Someone should do so and add a brief section and a few citations on mechanical induction.