Tumors :: sponges (Metazoan)::Evolution!?

Tumor as an atavistic process..

I recently attended a lecture by astrobiologist/physicist/cosmologist named Paul Davies. He gives a number of lectures each year on topics from physics like Quantum Mechanics, String Theory etc but nowadays he is working on the convergence of Biology and Physics at the Arizona State University (ASU).

The topic of the lecture was ‘Cancer Tumor as Metazoan 1.0 – Tapping genes of ancient ancestors’. The topic sounded so interesting that I had to know more about it. 

He started off with how he came about studying about such a thing. His curiosity grew after he came across an article in the ‘Nature’ which talked about the presence of tumor suppressor genes in sponges (A class of invertebrates).This got him going and he proposed his theory of cancer as follows –

"The genes of cellular cooperation that evolved with multicellularity about a billion years ago

are the same genes that malfunction to cause cancer. We hypothesize that cancer is an atavistic

condition that occurs when genetic or epigenetic malfunction unlocks an ancient ‘toolkit’ of

pre-existing adaptations, re-establishing the dominance of an earlier layer of genes that

controlled loose-knit colonies of only partially differentiated cells, similar to tumors."

What he meant by that is that cancer is an atavistic process. Why? Because some of the oncogenes have been traced back to as far as the age of primitive metazoans. Now explaining the title of this post, "These proto-metazoans were effectively small, loosely-knit ecosystems that fell short of the complex organization and regulation we associate with most modern metazoans. In short, proto-metazoans, which we dub

Metazoans 1.0, were tumor-like neoplasms." He further talked about features of tumors which apart from the genetic structure had resemblance to an ancient being. 

"Also zone between Metazoa 1.0 and Metazoa 2.0 may offer clues. Significantly, the polyp Hydra, the basal eukaryote referred to earlier in connection with the oncogene myc, has the power to regenerate itself, cancer-like, from a tiny fragment, and can go on doing so seemingly indefinitely. This ability is reminiscent of the immortalization seen in cancer cells, where the regulated cell divisions of somatic cells undergo an atavistic transformation to their previous less-regulated, premulticellular, proto-colonial reproductive regime."

The ability to conserve energy, i.e. Warburg effect (oxidative glycolysis). ‘Maybe the information for inducing cancer was already in the normal cell genome, waiting to be unmasked’. He exemplified it through the 'Safe mode' of computers which is activated once the computer faces some software/hardware insult. The evolution took place in such a way that the primitive genome after undergoing some epigenetic changes/minor changes evolved into a more complex/sophisticated  being. So in the face os trouble, reverting back to the earlier 'tumorigenic' being is the option it has. This is due to the lack of DNA repair mechanisms. Later in the Question and answer round, someone questioned into the rationale behind radiotherapy or such treatment modalities as according to him they too were dependent on mutating cells beyond their ablilty to survive. What if in that process, we uncover the 'tumorigenic being' via activation of the ancient toolkit? Interesting?! 

However he still posed certain 'grey areas' in his theory which need to be addressed, like, he has not been able to explain Angiogenesis which is a very advanced evolutionary process. Explaining 'Internal Darwinism' within tumors was fascinating. The ability of neoplasms to metastasise is an excellent example of 'selection' according to Davies. Sounds just fine, right?!

In the end, he chalked out his idea of developing 'Convergence of Systems biology and physics' in certain areas so that everything is more logical. One question by an oncologist was quite mind boggling. I will end this post with that question to ponder upon. 

"Biology is a branch of science where one thing leads to the other and that to the other and something is the result in the end. Just like evolution. But Physics is more discrete, it is like in 'packets'. How do you explain?"

Food for thought? (The food after the lecture was all I concentrated upon! Wine and cheese..Yum!) Well, for me understanding the question was very difficult! Answering and having an opinion on it it is..!

Links of the original article is as follows: http://cancer-insights.asu.edu/wp-content/uploads/2012/01/Cancer-tumors-as-Metazoa-1-0-tapping-genes-of-ancient-ancestors1.pdf

News for Paul Davies: http://www.telegraph.co.uk/science/science-news/9065707/The-final-frontier-in-the-war-on-cancer.html

Who is Paul Davies? : http://cosmos.asu.edu/index.html

Hope you had fun while reading! 

Comments and suggestions and interpretations are welcome.