Culturing cancer cells.......

A quickly yellowing and dust gathering booklet laid neglected since the day I submitted my Honors thesis, yet I had to fish it out from my bookshelf. A junior friend of mine wanted to know the format of a submitted thesis and being the obliging senior, I agreed to let him borrow my thesis.

I re-read the contents of my entire thesis and thankfully there was virtually zilch grammatical errors. However, I reflected on the work I had done and the similar works of other authors. I realized that an important consideration has often been overlooked, in the case of my work and others.

Allow me to give a brief introduction to my previous work. I was working on a pathway that is familiar to developmental biologists, the Wnt/beta catenin pathway, but I was studying the pathway in tumor cells. It's not uncommon for such pathways that are activated during the early development phase to be activated in cancer cell-lines. Oncofetal pathways is a more apt term used to describe them. Basically, I studied the activity of the pathways in highly metastatic cell-lines and compared them to poorly metastatic cell-lines, and examined the role of these pathways on the process of metastasis. I worked on colorectal cancer cell-lines and the highly metastatic cell-line is known to metastasize to the liver.

It is a norm to culture the different cell-lines individually in each culture vessel. I believe it would be more physiologically realistic to co-culture the cell-lines in a tissue culture instead of culturing the cell-line individually within a culture flask. The "seed" and "soil" concept is important in the event of metastasis. The crosstalk between the cancer cell (seed) and the organ microenvironment (soil) affects the outcome of metastasis. The organ microenvironment contains homeostatic factors that will determine the survival of the metastatic tumor cells (Fidler, 2003).

It comes as no surprise that the metastatic cell-lines should be grown in a hepatic tissue culture. Experiment-wise, my lab had originally isolated metastatic cell-lines from liver metastases, but had opted to culture the each cell-line individually in a culture flask. Hindsight is 20/20, and I thought it would have been better to co-culture each cell-line in a hepatic tissue culture. This would mimic the actual physiological conditions, and demonstrate the interplay of the seed and soil elements. The homeostatic factors secreted by the other cells in the tissue culture will interact with the tumor cell, and the outcome on the interested pathways and gene expression profile may possibly be different from the case whereby the tumor cell is cultured alone in a culture flask.

Hepatic tissue culture models comprising collagen embedded rat and human hepatocytes have already been utilized to study the pathogenic effects of parasites like tapeworm (Jura et al, 1996). I would think that such a model can be used to culture tumor cells.

Granted that poorly metastatic cells cannot grow in the hepatic tissue culture, nonetheless growing different metastatic cell-lines in the hepatic tissue culture would give us an idea on how each metastatic cell-line physiologically adapts to the microenvironment of the tissue culture through the induction or inhibition of certain pathways. Growing the metastatic cell-line in the hepatic tissue culture and making comparisons of gene expression and pathway activities to the same cell-line grown individually in the culture flask would give us an idea on how the metastatic tumor cell is affected by the surrounding milieu of the microenvironment provided by the hepatic tissue culture.

There are other tissue culture systems available that be used to study metastasizing tumor cells. For example, a neural tissue culture system can be utilized to study tumor cells that are known to metastasize to the brain. Admittedly the disadvantage of using such a co-culture system is the hassle that comes with the isolation of the tumor cells of interest. In that case, unique markers of these tumor cells have to be identified so that the tumor cells can be isolated using antibodies. However, it's extremely relevant to grow tumor cells in conditions that mimic the actual physiological conditions in order to obtain the most relevant conclusions. DARN, why didn't I think of this when I was writing my thesis. My discussion section would have looked less brief and for those students who have done similar experiments to what I have done for your research project, be prepared to be grilled on this point..............................................................

Citations
1) Fidler IJ. The pathogenesis of cancer metastasis: the 'seed and soil' hypothesis revisited. Nat Rev Cancer. 2003 Jun;3(6):453-8.

2) Jura H, Bader A, Hartmann M, Maschek H, Frosch M. Hepatic tissue culture model for study of host-parasite interactions in alveolar echinococcosis. Infect Immun. 1996 Sep;64(9):3484-90.

3) http://aiche.confex.com/aiche/2006/techprogram/P67759.HTM