The accumulation of soluble factors in the tumor microenvironment and their release into the bloodstream lead to systemic effects, resulting in cancer-associated syndromes such as cachexia. Another association observed in the latter scenario is chrono-disruption, which has been related with tumor onset and development. In fact, a positive relationship between master clock integrity and healthiness has already been disclosed; however, it is unclear whether the effects of chronodisruption in cancer are locally or systemically exerted. It is known that lung adenocarcinoma reprograms liver metabolism via a pro-inflammatory response without affecting liver clock genes. Our study evaluated whether a non-metastatic skin tumor can affect clock gene machinery of other organs.
Eight to sixteen-week old C57BL/6J male mice were inoculated subcutaneously with B16-F10 cells (or PBS, control animals), single housed at 22 ± 2 °C, kept under 12/12h light/dark cycle, and received food and water ad libitum. Two weeks after inoculation mice were euthanized 2 hours after lights on (ZT2) or 2 hours after lights off (ZT14). Skin of control animals and samples of non-tumoral adjacent skin, tumor, liver, lung, and brown adipose tissue (BAT) were collected to evaluate the expression of clock genes (Per1, Per2, Bmal1, and Nr1d1) by qPCR.
No oscillatory profile of clock genes was detected in skin of control animals, tumor adjacent skin, and tumor itself of inoculated animals; Bmal1 expression was reduced in adjacent skin and tumor as compared to skin of control animals. In liver and lung tissue, Per1 and Per2 oscillated in control animals, and tumor inoculation did not affect this oscillatory profile. Temporal oscillation of Bmal1 and Nr1d1 in the liver was lost in tumor-bearing mice. In BAT, Per1 and Bmal1 oscillatory expression was also lost in tumor-bearing mice. In all organs analyzed. Bmal1 transcript was reduced in tumor-bearing mice when compared to control animals.
The presence of a non-metastatic tumor in the skin alters clock machinery in adjacent skin, liver, lungs, and BAT. These data bring new knowledge of how tumor macro-environment affects clock machinery, resulting in a likely chrono-disruption of the organism as a result of a localized tumor in the skin.
Clinical trial identification
Legal entity responsible for the study
University of Sao Paulo (USP) and Sao Paulo Research Foundation (FAPESP)
Sao Paulo Research Foundation (FAPESP) and National Council of Technological and Scientific Development (CNPq).
All authors have declared no conflicts of interest.