Citations

Abstract NK cells mediate both direct cytotoxicity against a variety of tumor cells and indirect (FcR-dependent) cytotoxicity against antibody-coated targets. When cloned human NK cells (CD16+/CD3-) were exposed to NK-sensitive targets for 30 min, the level of inositol phosphates rose two to five times above background. The rise in inositol phosphates induced by NK-sensitive targets was paralleled by an increase in intracellular free calcium concentration ([Ca2+]i). A panel of tumor cells that were resistant to NK cell lysis did not stimulate significant levels of inositol phosphate production and did not induce an elevation of intracellular free calcium. Ligation of the FcR (CD16) with the mAb 3G8 also triggered phosphoinositide turnover. Kinetic experiments demonstrated that stimulation by either susceptible target cells or by FcR ligation led to rapid (less than 1 min) generation of the Ca2+-mobilizing second messenger, inositol trisphosphate, with slower accumulation of inositol bisphosphate and inositol monophosphate. Previous studies have demonstrated that activation of the cAMP-dependent second messenger pathway strongly inhibits NK cell-mediated cytotoxic functions. Treatment of NK effector cells with forskolin to elevate intracellular cAMP levels resulted in a concentration-dependent inhibition of phosphoinositide hydrolysis induced by both NK-sensitive targets and 3G8-mediated FcR ligation. These results suggest that phosphoinositide turnover represents a critical early event in the human NK cell cytolytic process. Moreover, the potent inhibitory effect of cAMP on NK cell cytotoxicity may be explained by the uncoupling of NK receptors from phospholipase C-mediated phosphoinositide hydrolysis.

The hypoxia‐inducible factor (HIF), HIF‐1, is a central regulator of the response to low oxygen or inflammatory stress and plays an essential role in survival and function of immune cells. However, the mechanisms regulating nonhypoxic induction of HIF‐1 remain unclear. Here, we assess the impact of germline heterozygosity of a novel, oxygen‐independent ubiquitin ligase for HIF‐1α: hypoxia‐associated factor (HAF; encoded by SART1). SART1−/− mice were embryonic lethal, whereas male SART1+/− mice spontaneously recapitulated key features of nonalcoholic steatohepatitis (NASH)‐driven hepatocellular carcinoma (HCC), including steatosis, fibrosis, and inflammatory cytokine production. Male, but not female, SART1+/− mice showed significant up‐regulation of HIF‐1α in circulating and liver‐infiltrating immune cells, but not in hepatocytes, before development of malignancy. Additionally, Kupffer cells derived from male, but not female, SART1+/− mice produced increased levels of the HIF‐1‐dependent chemokine, regulated on activation, normal T‐cell expressed and secreted (RANTES), compared to wild type. This was associated with increased liver‐neutrophilic infiltration, whereas infiltration of lymphocytes and macrophages were not significantly different. Neutralization of circulating RANTES decreased liver neutrophilic infiltration and attenuated HCC tumor initiation/growth in SART1+/− mice. Conclusion: This work establishes a new tumor‐suppressor role for HAF in immune cell function by preventing inappropriate HIF‐1 activation in male mice and identifies RANTES as a novel therapeutic target for NASH and NASH‐driven HCC. (Hepatology 2016;63:1576‐1591)

Abstract Clear-cell renal cell cancer (CRCC) is initiated typically by loss of the tumor-suppressor VHL, driving constitutive activation of hypoxia-inducible factor-1 (HIF1) and HIF2. However, whereas HIF1 has a tumor-suppressor role, HIF2 plays a distinct role in driving CRCC. In this study, we show that the HIF1α E3 ligase hypoxia-associated factor (HAF) complexes with HIF2α at DNA to promote HIF2-dependent transcription through a mechanism relying upon HAF SUMOylation. HAF SUMOylation was induced by hypoxia, whereas HAF-mediated HIF1α degradation was SUMOylation independent. HAF overexpression in mice increased CRCC growth and metastasis. Clinically, HAF overexpression was associated with poor prognosis. Taken together, our results show that HAF is a specific mediator of HIF2 activation that is critical for CRCC development and morbidity. Cancer Res; 75(2); 316–29. ©2014 AACR.

After therapeutic hormone deprivation, prostate cancer cells often develop androgen-insensitive growth through mechanisms thus far undefined. Neuropeptides have been previously implicated as growth factors in some prostate cancers. Here, we demonstrate that androgen-sensitive LNCaP human prostate cancer cells produce and secrete neurotensin following androgen withdrawal. We show that while LNCaP cells express the neurotensin receptor, only androgen-deprived cells exhibit a growth response to exogenous neurotensin. We further demonstrate that androgen-stimulated cells may be refractory to exogenous neurotensin due to androgen induction of a metalloprotease active toward neurotensin. Thus, prostate cancer cells deprived of androgen develop an alternative autocrine growth mechanism involving neurotensin.