We examined the cholesterol/protein ratio and the apoprotein composition of serum lipoproteins in a randomly selected population of maturity-onset diabetics and in a group of nondiabetics of similar age. We found no differences in cholesterol distribution between the groups as a whole, but diabetics with above-normal low-density lipoproteins (LDL) had decreased concentrations of high-density lipoprotein (HDL) cholesterol. In the diabetics as a whole, there was an increase in the cholesterol/protein ratio in HDL, a negative correlation between the amounts of LDL cholesterol and HDL cholesterol, an increase in the proportion of apolipoprotein C in very-low-density lipoprotein (VLDL), and a decrease in the proportion of the apolipoprotein AI component of HDL. In diabetic subjects with increased VLDL, there was an increase in the relative amount of apolipoprotein CIII, and a consequent decrease in the ratio of apolipoprotein CII/apolipoprotein CIII in the VLDL. In both diabetic and control subjects, apolipoprotein E and cholesterol content of VLDL were linearly related.

The effects of serum low-density lipoproteins (LDL) were studied in cultures of human skin fibroblasts grown in medium supplemented with human serum deficient in lipoproteins and in platelet factor. The LDL led to a temporary increase in the rate of cell replication, to increases in the cell content of protein and cholesterol, to an increase in average cell size, and to an increased secretion of glycosaminoglycans. The increases in cholesterol and protein were proportional to the increase in cell size, suggesting that the additional protein and cholesterol were of a structural, rather than a storage, nature. The increase in cell protein during the first few days of exposure to LDL was due to a decrease in the rate of protein degradation. Ultrafiltration of the serum to remove substances of molecular weight less than 30,000 did not reduce the basal rate of cell proliferation but did prevent the stimulation of proliferation by LDL; it did not alter the effect of LDL on cell protein and cholesterol, indicating that the latter responses are independent of the mitogenic action. The response of cells from diabetic donors did not differ from that of normal cells.

The role of hysterectomy in the development of pelvic floor dysfunction (PFD) remains widely disputed. The controversy is fueled by two key factors. The first is conflicting association studies that make it difficult to establish whether a link truly exists. Although many retrospective studies report a correlation between hysterectomy and increased risk of stress urinary incontinence (SUI) or pelvic organ prolapse (POP), prospective studies often fail to replicate these results, leading some to conclude that no association exists. However, most prospective studies do not follow up for a sufficient length of time to account for the long latency of PFD and cannot unilaterally prove the absence of an association. The second source of controversy is the absence of a plausible mechanism to explain how hysterectomy could predispose patients to PFD. In this paper, we investigate autonomic innervation and smooth muscle in the three layers of pelvic floor support and propose a mechanism through which autonomic damage from hysterectomy could predispose patients to PFD. We then identify key research areas needed to evaluate this theory. This report aims to inspire a discussion on how to further the collective understanding of the relationship between hysterectomy and PFD. Clarifying the nature of this connection could have enormous consequences in redefining the risks and benefits of hysterectomy.

There is an urgent need to develop new therapeutic or lifestyle strategies for treating ovarian cancer due to its high mortality and recurrence rate. In this regard, we found that cholesterol appears to be clinically important for ovarian cancer survival, highlighting it and its metabolism as potential therapeutic targets for improving the lifespan of patients. In a cohort of 153 patients, we found high total cholesterol or high LDL cholesterol was associated with high tumor grade, which in turn was associated with poor survival. Additionally, patients prescribed cholesterol lowering drugs such as statins, cholesterol absorption inhibitors or fiber were associated with significantly improved overall survival. We did not observe significant differences between statins and other cholesterol lowering drugs, indicating the effects observed were most likely due to cholesterol lowering rather than other unintended pharmacologic properties of statins. Cytochrome P450 enzymes catalyze the first steps in cholesterol metabolism pathways. Among them, CYP27A1 is highly expressed in myeloid cells and oxidizes cholesterol into 27-hydroxychoelsterol (27HC), which is the most abundant oxysterol and an endogenous signaling molecule. Analysis of publicly available databases indicated that low tumoral CYP27A1 expression was associated with better progression-free survival and overall survival. Conversely, high tumoral CYP7B1 expression, the enzyme that metabolites 27HC, was associated with improved progression-free survival. Therefore, we hypothesized that CYP27A1/27HC might be mediating the effects of cholesterol on cancer survival. Indeed, we found ovarian tumors failed to grow in CYP27A1−/− mice, eventually completely regressing, while treatment with exogenous 27HC was able to sustain tumor growth in CYP27A1−/− mice, indicating that CYP27A1/27HC are important for ovarian cancer progression. Analysis of tumors and lymphoid tissues suggested that 27HC was associated with compromised immunosurveillance. Specifically, CYP27A1/27HC-axis altered the recruitment of 1) monocytic-MDSCs, an immunosuppressive subtype of myeloid cells, 2) antigen-presenting myeloid cells, and 3) CD4+ T cells. Thus, the CYP27A1/27HC-axis presents an alternative path for cancer associated immunosuppression, offering a potentially novel therapeutic target. We tested the therapeutic utility of targeting this axis and found that a small molecule CYP27A1 inhibitor significantly improved the efficacy of anti-PDL1 checkpoint inhibition in a preclinical model. Collectively, our data suggest that cholesterol/27HC-axis modulates the ovarian tumor microenvironment and promotes cancer progression, revealing a novel therapeutic target for the treatment of ovarian cancer. Supported by: NIH R01CA234025 (E.R.N.), a Cancer Scholars for Translational and Applied Research (C*STAR) Award (S.H.) and NIH T32EB019944 (S.H.). Citation Format: Sisi He, Georgina Cheng, Edward Roy, Marta Spain, Ronald Kimball, Nikolas Snyder, Melina Salgado, Debby Vannoy, Betsy Barnick, Liqian Ma, Varsha Vembar, Anna Vardanyan, Amy Baek, Joanna Burdette, Erik R. Nelson. Cholesterol and its metabolism impact ovarian cancer progression [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2821.

Ovarian cancer continues to have a high mortality and recurrence rate. Hence, there is an urgent need to develop new therapeutic or lifestyle strategies. In this regard, epidemiologic studies have implicated elevated cholesterol as a negative prognostic factor. Conversely, ovarian cancer patients prescribed cholesterol-lowering drugs (HMGCoA-R inhibitors; statins) exhibit significantly increased progression-free survival (PFS). In a cohort of 134 patients, we found high LDL cholesterol (≥130 mg/dL) is also associated with high tumor grade at diagnosis. Therefore, cholesterol appears to be clinically important for the progression of ovarian cancer. These observations highlight the potential relevance of previous work implicating the cholesterol metabolite, 27-hydroxychoelsterol (27HC), as a ligand for the estrogen and liver x receptors, providing a putative mechanism for the actions of cholesterol. CYP27A1 encodes the first enzyme in the alternative pathway of cholesterol catabolism, producing 27HC. Analysis of TCGA and other publicly available databases indicated that low CYP27A1 expression was associated with increased PFS. Conversely, high CYP7B1 expression, the enzyme that metabolizes 27HC, was associated with increased PFS. Therefore, we hypothesized that CYP27A1 is involved in ovarian cancer pathophysiology via 27HC signaling. To directly investigate the role of CYP27A1 in ovarian cancer progression, we monitored the growth of tumors grafted into the ovarian bursa area of wild-type and CYP27A1 knockout (KO) mice. Strikingly, we found that ovarian tumors failed to thrive in CYP27A1 KO mice, eventually completely regressing. Treatment with exogenous 27HC was able to sustain tumor growth in CYP27A1 KO mice, indicating that it was indeed a deficiency in 27HC that was mediating the antitumor effects in these mice. Somewhat paradoxically, we found 27HC had growth inhibitory effects on in vitro proliferation of ovarian cancer cells. However, analysis of tumors indicated that 27HC treatment was associated with the enrichment of certain myeloid populations, especially M-MDSCs. M-MDSCs are a myeloid-immune cell type known to be protumorigenic, at least in part through their suppression of cytotoxic CD8+ T cells. This would suggest that inhibition of CYP27A1 might improve the efficacy of immune checkpoint inhibition. Therefore, we tested the therapeutic utility of combining a small-molecule inhibitor of CYP27A1 with anti-PD-L1. Indeed, combining these two approaches significantly decreased ovarian tumor growth in a preclinical model. Collectively, our preliminary data indicate that cholesterol/27HC-axis modulates myeloid cells within tumor microenvironment and promotes cancer progression, revealing a novel therapeutic target for ovarian cancer treatments. Supported by NIH NCI R00CA172357 (E.R.N.), NIH NCI R01CA234025 (E.R.N.), a Cancer Scholars for Translational and Applied Research (C*STAR) Award (S.H.) and NIH T32EB019944 (S.H.). Citation Format: Sisi He, Liqian Ma, Georgina Cheng, Betsy Barnick, Marta Spain, Ronald Kimball, Amy E. Baek, Joanna Burdette, Erik R. Nelson. The impact of cholesterol and its metabolites on ovarian tumor microenvironment and cancer progression [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B105.