Mammalian tumor-like organs. 1. The role of tumor-like normal organs and atypical tumor organs in the evolution of development (carcino-evo-devo)

Abstract

Background Earlier I hypothesized that hereditary tumors might participate in the evolution of multicellular organisms. I formulated the hypothesis of evolution by tumor neofunctionalization, which suggested that the evolutionary role of hereditary tumors might consist in supplying evolving multicellular organisms with extra cell masses for the expression of evolutionarily novel genes and the origin of new cell types, tissues, and organs. A new theory—the carcino-evo-devo theory—has been developed based on this hypothesis. Main text My lab has confirmed several non-trivial predictions of this theory. Another non-trivial prediction is that evolutionarily new organs if they originated from hereditary tumors or tumor-like structures, should recapitulate some tumor features in their development. This paper reviews the tumor-like features of evolutionarily novel organs. It turns out that evolutionarily new organs such as the eutherian placenta, mammary gland, prostate, the infantile human brain, and hoods of goldfishes indeed have many features of tumors. I suggested calling normal organs, which have many tumor features, the tumor-like organs. Conclusion Tumor-like organs might originate from hereditary atypical tumor organs and represent the part of carcino-evo-devo relationships, i.e., coevolution of normal and neoplastic development. During subsequent evolution, tumor-like organs may lose the features of tumors and the high incidence of cancer and become normal organs without (or with almost no) tumor features.

Mammalian tumor-like organs. 2. Mammalian adipose has many tumor features and obesity is a tumor-like process

“…Several non-trivial predictions of the main hypothesis have been confirmed in my laboratory ([ 1 – 4 ], reviewed in [ 5 ]). One non-trivial prediction of the main hypothesis is that evolutionarily novel organs if they indeed originated from hereditary tumors or tumor-like structures, should recapitulate some features of tumors in their development.…”

“…One non-trivial prediction of the main hypothesis is that evolutionarily novel organs if they indeed originated from hereditary tumors or tumor-like structures, should recapitulate some features of tumors in their development. That is why in previous articles [ 2 , 3 , 5 ] I was looking for the data that might confirm this prediction in the literature, and also performed some experiments in my lab. The first paper in this series [ 5 ] reviewed the evidence that evolutionarily novel organs such as the placenta, mammary gland, prostate, and infantile brain indeed have many features of tumors including the regulated invasiveness at certain stages of their development and higher incidence of cancer.…”

“…As discussed earlier, other evolutionarily novel organs of mammals, such as the placenta, mammary gland, and prostate, also have many tumor features [ 2 , 5 ]. However, evolutionarily older organs are characterized by lower cancer rates [ 26 ] and do not have (or have fewer) tumor features.…”

“…However, evolutionarily older organs are characterized by lower cancer rates [ 26 ] and do not have (or have fewer) tumor features. The author suggested calling normal organs, which have many tumor features, the "tumor-like organs" [ 3 , 5 ]. We may conclude that mammalian adipose is a tumor-like organ and obesity is a tumor-like process.…”

“…The first paper in this series [ 5 ] reviewed the evidence that evolutionarily novel organs such as the placenta, mammary gland, prostate, and infantile brain indeed have many features of tumors including the regulated invasiveness at certain stages of their development and higher incidence of cancer. In that paper, I suggested calling evolutionarily new normal organs, which have many tumor features, the tumor-like organs for brevity [ 5 ].…”