IS CANCER UNIQUE TO COMPLEX LIFE ON EARTH OR A UNIVERSAL PHENOMENON FOR ALL MULTICELLULAR LIFE IN THE UNIVERSE

Introduction: The phenomenon of cancer involves the uncontrolled growth of a certain type of cells within an organism that often results in the demise of that organism. Cancer cells tap into an immense repertoire of biochemical pathways to deceive both the immune system and our medical strategies to avoid destruction and continue with unproliferated growth, re-building of blood vessels to serve their feeding purposes, and spreading to new locations within the host organism. Cancer is one of the leading causes of death in industrialized countries. Though we have spent billions of dollars to find a cure for cancer, there are only very few success stories. This begs the question why we find it so hard to stop the rampage of cancer cells. We previously hypothesized that cancer is more than an accident, a utilization of a primordial mechanism, perhaps an escape mechanism that microorganisms used in biofilms or other communal bacterial aggregates to leave the collective in times of starvation and environmental stress [1]. If so, cancer is to be expected an ancient mechanism prevalent in all multicellular life. This also invites the question of whether cancer would be a re-occurring phenomenon if the evolution of multicellular life on Earth would be replayed. And is cancer common to life on Earth only, or also to multicellular life elsewhere in the universe? The Road to Multicellular Life: It is not clear what the decisive step was from unicellular life to multicellular life in the evolution of life on Earth. Neither the conditions nor the critical selective variables for this critical transition are clearly understood. Colonial communities, such as those that gave rise to the Proterozoic stromatolites, represent early aggregates of prokaryotic organisms that perhaps functioned independently but aggregated into a macroorganismic superstructure. A distinctive assemblage of freshwater calcite microbialites discovered at Pavilion Lake, British Columbia, Canada [2] may suggest a transitional form from the exclusively prokaryotic colonial precursors of the stromatolites to the multicellular organismic aggregates that give rise to coral reefs. The distinctive assemblage of freshwater calcite microbialites at Pavilion Lake has been associated with organisms such as Epiphyton and Girvanella, fossils from just before the Cambrian explosion about 550 million years ago [3]. The microbialites of Pavilion Lake bear clear analogy to stromatolites – the mineralogical remnants of paleomicrobialites prominent in the fossil record. They differ from them in their modern (essentially contemporary) origin and in a substantial eukaryotic contribution to their biomass. The complexity of the resulting community structure, in fact, suggests the possibility of a functional organismic aggregate capable of more complex biological processes than those organisms that created the stromatolites. Some of the microbial aggregates appear to have functional properties, for example the artichoke structure optimized for the collection of light (Fig 1.C) and the chimney structures, 530 cm tall, with a central conduit, which are in their function reminiscent of the functional properties of sponges, usually considered the most primitive of multicellular organisms (Fig. 1B). The microbialite communities found at Pavilion Lake differ from coral reefs in being composed primarily of microorganisms, and predominantly of prokaryotes. At least some of these prokaryotes communicate by quorum sensing based on the LuxS and SahH gene sequences we recovered. Certainly, the complex interaction of these microbial cells is not equivalent to the collaboration of cells within an individual multicellular organism, where each cell has the same genetic information, but differential gene expression is providing well-defined cellular specializations. However, their long-term intimate cohabitation is well suited for intercellular chemical signalling and functional coordination, and increases the opportunity for some degree of genetic exchange over evolutionary time that could encode their mutual interactions into a “community” genetic program [4]. It is not inconceivable that a community genetic structure could give rise to a multicellular aggregate which functions in a coordinated manner somewhat like a multicellular organism, much as the semi-autonomous cells of a sponge function as a quasi-multicellular organism, but with substantially more complexity. A somewhat reminiscent behaviour can be observed in slide molds that cluster together and act as one organism when certain chemical signals are received.