Oncogenes, tumor suppressor and differentiation genes represent the oldest human gene classes and evolve concurrently.

Earlier we showed that human genome contains many evolutionarily young or novel genes with tumor-specific or tumor-predominant expression. We suggest calling such genes Tumor Specifically Expressed, Evolutionarily New (TSEEN) genes. In this paper we performed a study of the evolutionary ages of different classes of human genes, using homology searches in genomes of different taxa in human lineage. We discovered that different classes of human genes have different evolutionary ages and confirmed the existence of TSEEN gene classes. On the other hand, we found that oncogenes, tumor-suppressor genes and differentiation genes are among the oldest gene classes in humans and their evolution occurs concurrently. These findings confirm non-trivial predictions made by our hypothesis of the possible evolutionary role of hereditary tumors. The results may be important for better understanding of tumor biology. TSEEN genes may become the best tumor markers.

The novelty of human cancer/testis antigen encoding genes in evolution.

In order to be inherited in progeny generations, novel genes should originate in germ cells. Here, we suggest that the testes may play a special "catalyst" role in the birth and evolution of new genes. Cancer/testis antigen encoding genes (CT genes) are predominantly expressed both in testes and in a variety of tumors. By the criteria of evolutionary novelty, the CT genes are, indeed, novel genes. We performed homology searches for sequences similar to human CT in various animals and established that most of the CT genes are either found in humans only or are relatively recent in their origin. A majority of all human CT genes originated during or after the origin of Eutheria. These results suggest relatively recent origin of human CT genes and align with the hypothesis of the special role of the testes in the evolution of the gene families.