Mucci, Lorelei A.

77 Background: Prostate cancer cells rely on cholesterol for proliferation and androgen production. We recently demonstrated that increased expression of the second key enzyme of cholesterol synthesis, squalene monooxygenase (SQLE), is associated with higher prostate cancer-specific mortality (PCSM). We here validate findings in two additional prospective studies and investigate putative mechanisms. Methods: We analyzed the prospective prostatectomy cohorts within the Health Professionals Follow-up Study (HPFS) and the Physicians’ Health Study (PHS) as well as initially expectantly managed patients in the Swedish Watchful Waiting Study (SWWS). 258 lethal cancer cases and 469 patients who survived > 8 years without metastases were included. SQLE mRNA was measured in tumor specimens at diagnosis of all patients and in benign prostate tissue of 197 patients. Markers of tumor angiogenesis were assessed via immunohistochemistry in 169 HPFS patients. We estimated multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression. Results: Higher SQLE expression was confirmed to be predictive of higher PCSM in the validation prostatectomy cohort PHS. Combining the two prostatectomy cohorts, men with high SQLE expression ( > 1 standard deviation above the mean) were 6.7 times (95% CI, 2.9 to 15.8; p < 0.001) more likely to die from their cancer compared to men with the mean level of SQLE expression. A 10% higher ratio of SQLE mRNA expression in tumor vs. benign prostate tissue of the same patient was predictive of 42% higher PCSM (95% CI, 15% to 74%). Higher SQLE expression was strongly associated with increased angiogenesis markers (all p ≤ 0.001). This increased risk associated with high SQLE expression was not modified by statin use (p ≥ 0.52). In initially untreated patients in SWWS, a more modest association of tumor SQLE expression with PCSM was observed (p = 0.047). Conclusions: SQLE, the second rate-limiting enzyme of cholesterol synthesis, is associated with prostate cancer progression. Its expression at cancer diagnosis is predictive of lethal disease both after curative-intent prostatectomy and in a watchful waiting setting, possibly by facilitating micrometastatic disease.

Abstract BACKGROUND: We previously showed that mRNA expression of squalene monooxygenase (SQLE), part of the cholesterol synthesis pathway, is associated with lethal prostate cancer. In-vitro studies suggest that loss of PTEN expression and resulting PI3K pathway activation drive cholesterol ester accumulation in aggressive prostate cancers through sterol regulatory element-binding protein (SREBP) and acyl coenzyme A-cholesterol acyltransferase (ACAT1) activity. In two prospective cohorts, we studied whether lower PTEN expression is associated with cholesterol metabolism and how this relates to lethal prostate cancer. METHODS: We analyzed men with prostate cancer from the prospective prostatectomy Health Professionals Follow-up Study and Physicians’ Health Study. 105 men had lethal cancer and 284 men non-lethal disease without metastases at 8 years of follow-up. Whole-transcriptome mRNA expression profiling data was available from diagnostic prostate tumor specimens. Linear regression models were used to assess continuous and categorical associations, and Pearson correlation coefficients were calculated. Logistic regression was used to obtain odds ratios (ORs) and 95% confidence intervals (CIs) of lethal prostate cancer. RESULTS: Both lower PTEN and higher SQLE expression were associated with higher Gleason grade (p trend &lt; 0.001 each). Correlations of PTEN with SREBF1 (r = -0.08, p = 0.1), SREBF2 (r = -0.09, p = 0.07), and ACAT1 (r = 0.04, p = 0.4) were weak. SREBF2 was correlated with SQLE (r = 0.33, p &lt; 0.001) but not with ACAT1 (r = -0.01, p = 0.8). Low PTEN was associated with lethal cancer (OR, 1.50 per 1 standard deviation [SD] decrease; 95% CI, 1.20 to 1.87; p = 0.001). High SQLE was associated with lethal cancer (OR 2.13 per 1 SD increase, 95% CI, 1.63 to 2.79; p &lt; 0.001). SREBF1, SREBF2, and ACAT1 were not associated with lethal cancer (all p &gt; 0.05). Adjusting for PTEN mildly attenuated the association of SQLE with lethal cancer (OR, 2.07; 95% CI, 1.57 to 2.73), as did additional adjustment for age, Gleason grade, and stage (SQLE: OR, 1.75; 95% CI, 1.29 to 2.40). In the lowest quartile of PTEN expression, SQLE was less strongly associated with lethal cancer (OR 1.74; 95% CI, 1.20 to 2.52) compared to the upper three quartiles (OR 2.47; 95% CI, 1.69 to 3.60; p interaction = 0.2). CONCLUSION: Low PTEN mRNA expression and high SQLE are features of aggressive prostate cancers. However, at the time of prostatectomy, SREBF1/2 expression and resulting ACAT1 expression do not appear to be major characteristics of prostate cancers with lethal outcomes. Citation Format: Konrad H. Stopsack, Travis A. Gerke, Lorelei A. Mucci, Jennifer R. Rider. PTEN expression, cholesterol metabolism, and lethal prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 60.

Abstract Cholesterol metabolism has been implicated in prostate cancer pathogenesis. Here, we assessed the association of intratumoral mRNA expression of cholesterol synthesis enzymes, transporters, and regulators in tumor specimen at diagnosis and lethal prostate cancer, defined as mortality or metastases from prostate cancer in contrast to nonlethal disease without evidence of metastases after at least 8 years of follow-up. We analyzed the prospective prostate cancer cohorts within the Health Professionals Follow-up Study (n = 249) and the Physicians' Health Study (n = 153) as well as expectantly managed patients in the Swedish Watchful Waiting Study (n = 338). The expression of squalene monooxygenase (SQLE) was associated with lethal cancer in all three cohorts. Men with high SQLE expression (&gt;1 standard deviation above the mean) were 8.3 times (95% confidence interval, 3.5 to 19.7) more likely to have lethal cancer despite therapy compared with men with the mean level of SQLE expression. Absolute SQLE expression was associated with lethal cancer independently from Gleason grade and stage, as was a SQLE expression ratio in tumor versus surrounding benign prostate tissue. Higher SQLE expression was tightly associated with increased histologic markers of angiogenesis. Collectively, this study establishes the prognostic value of intratumoral cholesterol synthesis as measured via SQLE, its second rate-limiting enzyme. SQLE expression at cancer diagnosis is prognostic for lethal prostate cancer both after curative-intent prostatectomy and in a watchful waiting setting, possibly by facilitating micrometastatic disease. Cancer Res; 76(16); 4785–90. ©2016 AACR.

Abstract Purpose: Prostate cancers incite tremendous morbidity upon metastatic growth. We previously identified Asporin (ASPN) as a potential mediator of metastatic progression found within the tumor microenvironment. ASPN contains an aspartic acid (D)-repeat domain and germline polymorphisms in D-repeat-length have been associated with degenerative diseases. Associations of germline ASPN D polymorphisms with risk of prostate cancer progression to metastatic disease have not been assessed. Experimental Design: Germline ASPN D-repeat-length was retrospectively analyzed in 1,600 men who underwent radical prostatectomy for clinically localized prostate cancer and in 548 noncancer controls. Multivariable Cox proportional hazards models were used to test the associations of ASPN variations with risk of subsequent oncologic outcomes, including metastasis. Orthotopic xenografts were used to establish allele- and stroma-specific roles for ASPN D variants in metastatic prostate cancer. Results: Variation at the ASPN D locus was differentially associated with poorer oncologic outcomes. ASPN D14 [HR, 1.72; 95% confidence interval (CI), 1.05–2.81, P = 0.032] and heterozygosity for ASPN D13/14 (HR, 1.86; 95% CI, 1.03–3.35, P = 0.040) were significantly associated with metastatic recurrence, while homozygosity for the ASPN D13 variant was significantly associated with a reduced risk of metastatic recurrence (HR, 0.44; 95% CI, 0.21–0.94, P = 0.035) in multivariable analyses. Orthotopic xenografts established biologic roles for ASPN D14 and ASPN D13 variants in metastatic prostate cancer progression that were consistent with patient-based data. Conclusions: We observed associations between ASPN D variants and oncologic outcomes, including metastasis. Our data suggest that ASPN expressed in the tumor microenvironment is a heritable modulator of metastatic progression. Clin Cancer Res; 22(2); 448–58. ©2015 AACR.

Abstract A genome-wide association study (GWAS) of prostate cancer in Kaiser Permanente health plan members (7,783 cases, 38,595 controls; 80.3% non-Hispanic white, 4.9% African-American, 7.0% East Asian, and 7.8% Latino) revealed a new independent risk indel rs4646284 at the previously identified locus 6q25.3 that replicated in PEGASUS (N = 7,539) and the Multiethnic Cohort (N = 4,679) with an overall P = 1.0 × 10−19 (OR, 1.18). Across the 6q25.3 locus, rs4646284 exhibited the strongest association with expression of SLC22A1 (P = 1.3 × 10−23) and SLC22A3 (P = 3.2 × 10−52). At the known 19q13.33 locus, rs2659124 (P = 1.3 × 10−13; OR, 1.18) nominally replicated in PEGASUS. A risk score of 105 known risk SNPs was strongly associated with prostate cancer (P &lt; 1.0 × 10−8). Comparing the highest to lowest risk score deciles, the OR was 6.22 for non-Hispanic whites, 5.82 for Latinos, 3.77 for African-Americans, and 3.38 for East Asians. In non-Hispanic whites, the 105 risk SNPs explained approximately 7.6% of disease heritability. The entire GWAS array explained approximately 33.4% of heritability, with a 4.3-fold enrichment within DNaseI hypersensitivity sites (P = 0.004). Significance: Taken together, our findings of independent risk variants, ethnic variation in existing SNP replication, and remaining unexplained heritability have important implications for further clarifying the genetic risk of prostate cancer. Our findings also suggest that there may be much promise in evaluating understudied variation, such as indels and ethnically diverse populations. Cancer Discov; 5(8); 878–91. ©2015 AACR. This article is highlighted in the In This Issue feature, p. 783