Increased Fibrosis in White Adipose Tissue of Male and Female bGH Transgenic Mice Appears Independent of TGF-ß Action.

Fibrosis is a pathological state caused by excess deposition of extracellular matrix proteins in a tissue. Male bovine growth hormone (bGH) transgenic mice experience metabolic dysfunction with a marked decrease in lifespan and with increased fibrosis in several tissues including white adipose tissue (WAT), which is more pronounced in the subcutaneous (Sc) depot. The current study expanded on these initial findings to evaluate WAT fibrosis in female bGH mice and the role of transforming growth factor (TGF)-ß in the development of WAT fibrosis. Our findings established that female bGH mice, like males, experience a depot-dependent increase in WAT fibrosis, and bGH mice of both sexes have elevated circulating levels of several markers of collagen turnover. Using various methods, TGF-ß signaling was found unchanged or decreased-as opposed to an expected increase-despite the marked fibrosis in WAT of bGH mice. However, acute GH treatments in vivo, in vitro, or ex vivo did elicit a modest increase in TGF-ß signaling in some experimental systems. Finally, single nucleus RNA sequencing confirmed no perturbation in TGF-ß or its receptor gene expression in any WAT cell subpopulations of Sc bGH WAT; however, a striking increase in B lymphocyte infiltration in bGH WAT was observed. Overall, these data suggest that bGH WAT fibrosis is independent of the action of TGF-ß and reveals an intriguing shift in immune cells in bGH WAT that should be further explored considering the increasing importance of B cell-mediated WAT fibrosis and pathology.

Growth hormone receptor antagonism downregulates ATP-binding cassette transporters contributing to improved drug efficacy against melanoma and hepatocarcinoma in vivo.

Knockdown of GH receptor (GHR) in melanoma cells in vitro downregulates ATP-binding cassette-containing (ABC) transporters and sensitizes them to anti-cancer drug treatments. Here we aimed to determine whether a GHR antagonist (GHRA) could control cancer growth by sensitizing tumors to therapy through downregulation of ABC transporters in vivo. We intradermally inoculated Fluc-B16-F10 mouse melanoma cells into GHA mice, transgenic for a GHR antagonist (GHRA), and observed a marked reduction in tumor size, mass and tumoral GH signaling. Moreover, constitutive GHRA production in the transgenic mice significantly improved the response to cisplatin treatment by suppressing expression of multiple ABC transporters and sensitizing the tumors to the drug. We confirmed that presence of a GHRA and not a mere absence of GH is essential for this chemo-sensitizing effect using Fluc-B16-F10 allografts in GH knockout (GHKO) mice, where tumor growth was reduced relative to that in GH-sufficient controls but did not sensitize the tumor to cisplatin. We extended our investigation to hepatocellular carcinoma (HCC) using human HCC cells in vitro and a syngeneic mouse model of HCC with Hepa1-6 allografts in GHA mice. Gene expression analyses and drug-efflux assays confirm that blocking GH significantly suppresses the levels of ABC transporters and improves the efficacy of sorafenib towards almost complete tumor clearance. Human patient data for melanoma and HCC show that GHR RNA levels correlate with ABC transporter expression. Collectively, our results validate in vivo that combination of a GHRA with currently available anti-cancer therapies can be effective in attacking cancer drug resistance.