The effects of glycemic index on prostate cancer progression in a xenograft mouse model

BACKGROUND

Previously, we found low-carbohydrate diets slowed prostate cancer (PC) growth and increased survival vs. a Western diet in mice, by inhibiting the insulin/IGF-1 axis. Thus, we tested whether modifying carbohydrate quality to lower glycemic index (GI) without changing quantity results in similar benefits as with reduced quantity.

METHODS

Male SCID mice injected with LAPC-4 cells were single-housed and randomized when their tumors reached 200 mm3 on average to a LoGI (48% carbohydrate kcal, from Hylon-VII) or HiGI Western diet (48% carbohydrate kcal, from sucrose). Body weight and tumor volume were measured weekly. Body composition was assessed 35 days after randomization. Blood glucose and serum insulin, IGF-1 and IGFBP3 were measured at study end when tumor volumes reached 800 mm3. We analyzed gene expression of mice tumors by RNA-sequencing and human tumors using the Prostate Cancer Transcriptome Atlas.

RESULTS

There were no significant differences in tumor volume (P > 0.05), tumor proliferation (P = 0.29), and overall survival (P = 0.15) between groups. At 35 days after randomization, the LoGI group had 30% lower body fat (P = 0.007) despite similar body weight (P = 0.58). At sacrifice, LoGI mice had smaller livers (P < 0.001) and lower glucose (P = 0.15), insulin (P = 0.11), IGF-1 (P = 0.07) and IGF-1:IGFBP3 ratio (P = 0.05), and higher IGFBP3 (P = 0.09) vs. HiGI, although none of these metabolic differences reached statistical significance. We observed differential gene expression and pathway enrichment in mice tumors by diet. The most upregulated and downregulated gene in the LoGI group showed expression patterns more closely resembling expression in human benign prostate tissue vs. PC.

CONCLUSIONS

In this single mouse xenograft model, consuming a low GI diet did not delay PC growth or survival vs. a high GI diet despite suggestions of decreased activation of the insulin/IGF-1 pathway. These data suggest that improving carbohydrate quality alone while consuming a high carbohydrate diet may not effectively slow PC growth.

Racial differences in circulating mitochondria-derived peptides may contribute to prostate cancer health disparities

INTRODUCTION

The mitochondrial genome has small open reading frames (sORF) which produce measurable mitochondrial-derived peptides (MDPs), including humanin, SHLP2, and MOTS-c. Previously, among men undergoing prostate biopsy, we found higher serum SHLP2 was linked with lower prostate cancer (PC) risk in European American men (EAM), while null associations were found in African American men (AAM). Here, in different patients undergoing prostate biopsy, we tested the link between SHLP2, humanin and MOTS-c and PC risk by race.

METHODS

Plasma SHLP2, humanin, and MOTS-c were measured in 198 men (50/49 EAM/AAM cases; 50/49 EAM/AAM controls) undergoing biopsy. Logistic and multinomial regression models tested associations between each MDP and PC diagnosis, low-grade (grade group, GG1) and high-grade (GG2-5). Models were adjusted for age, body mass index, digital rectal examination, and prostate specific antigen (PSA). We tested interactions between MDPs and race.

RESULTS

Among controls, humanin was similar by race (p = 0.60), but both SHLP2 (p = 0.007) and MOTS-c (p = 0.026) were lower in AAM controls versus EAM controls. Among EAM, higher MDP values were associated with lower PC risk (all p ≤ 0.001), with null associations in AAM (all p-interactions ≤ 0.01). Similarly, higher MDP expression was associated with decreased risk of low- and high-grade PC in EAM (all p ≤ 0.005) with null associations in AAM.

CONCLUSIONS

Higher MDP levels were associated with lower PC risk in EAM but not AAM. Generally, AAM controls had lower MDP levels. These data support MDPs and mitochondrial dysfunction in PC, suggesting greater dysfunction in AAM may contribute to excess PC risk. Future larger studies are needed to confirm these results.

The influence of low-carbohydrate diets on the metabolic response to androgen-deprivation therapy in prostate cancer

BACKGROUND

Prostate cancer (PC) is the second most lethal cancer for men. For metastatic PC, standard first-line treatment is androgen deprivation therapy (ADT). While effective, ADT has many metabolic side effects. Previously, we found in serum metabolome analysis that ADT reduced androsterone sulfate, 3-hydroxybutyric acid, acyl-carnitines but increased serum glucose. Since ADT reduced ketogenesis, we speculate that low-carbohydrate diets (LCD) may reverse many ADT-induced metabolic abnormalities in animals and humans.

METHODS

In a multicenter trial of patients with PC initiating ADT randomized to no diet change (control) or LCD, we previously showed that LCD intervention led to significant weight loss, reduced fat mass, improved insulin resistance, and lipid profiles. To determine whether and how LCD affects ADT-induced metabolic changes, we analyzed serum metabolites after 3-, and 6-months of ADT on LCD versus control.

RESULTS

We found androsterone sulfate was most consistently reduced by ADT and was slightly further reduced in the LCD arm. Contrastingly, LCD intervention increased 3-hydroxybutyric acid and various acyl-carnitines, counteracting their reduction during ADT. LCD also reversed the ADT-reduced lactic acid, alanine, and S-adenosyl methionine (SAM), elevating glycolysis metabolites and alanine. While the degree of androsterone reduction by ADT was strongly correlated with glucose and indole-3-carboxaldehyde, LCD disrupted such correlations.

CONCLUSIONS

Together, LCD intervention significantly reversed many ADT-induced metabolic changes while slightly enhancing androgen reduction. Future research is needed to confirm these findings and determine whether LCD can mitigate ADT-linked comorbidities and possibly delaying disease progression by further lowering androgens.

Abstract 3511: Racial differences in circulating mitochondria-derived peptides may contribute to prostate cancer health disparities

INTRODUCTION AND OBJECTIVES: Our group identified multiple small open reading frames (ORFs) in the mitochondrial genome. These ORFs produce small mitochondrial-derived peptides (MDPs) that are measurable in plasma including humanin, small humanin-like peptide-2 (SHLP2), and mitochondrial open reading frame of the 12S rRNA (MOTSc). Previously we found that higher serum SHLP2 was linked with lower prostate cancer (PC) risk in white men, but no significant association was observed in black men. We tested whether SHLP2 and other MDPs as measured in plasma correlated with PC risk by race in a separate sample of men undergoing prostate biopsy. METHODS: Plasma SHLP2, humanin, and MOTSc were measured by ELISA in 198 men (50/49 white/black cases; 50/49 white/black controls) undergoing prostate biopsy at the Durham Veterans Affair hospital. Logistic and multinomial regression models were used to test the association between each MDP and PC diagnosis and low-grade (grade group 1) and high-grade PC (grade group 2-5). Models were adjusted for age, body mass index, digital rectal examination, and PSA. We tested the interaction between MDPs and race in predicting PC. RESULTS: There was a statistically significant p-interaction between all 3 MDPs and race for predicting PC (all p-interactions values lower than 0.01). Among white men, higher values of all MDPs were significantly associated with lower PC diagnosis (all p-values lower than 0.001). In contrast, in black men, all MDPs were unrelated to PC diagnosis. Similarly, higher expression of all MDPs was associated with decreased risk of both low- and high-grade PC in white men (all p-values lower than 0.005) but none were associated with low- or high-grade in black men. Black controls had lower MOTSc (p-value equal 0.026) and SHLP2 (p-value equal 0.001) values than white controls. CONCLUSIONS: Higher expression of all three MDPs studied (plasma SHLP2, humanin, and MOTSc) were associated with lower PC risk in white men but not in black men. However, in general, black controls had lower MDP levels than white controls. These data support the importance of MDPs and perhaps mitochondrial dysfunction in PC and suggest greater dysfunction in black men (lower MDP levels in controls), which may contribute to excess PC risk in black men, though this requires confirmation in future larger studies. Funding: Supported in part by DODW81XWH, K24CA160653, and U54CA233465.

Citation Format: Adela Ramirez-Torres, Allison L. Reagan, Lauren E. Howard, Emily Wiggins, Adriana C. Vidal, Junxiang Wang, Stephen J. Freedland, Pinchas Cohen. Racial differences in circulating mitochondria-derived peptides may contribute to prostate cancer health disparities [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 3511.

Macrophage HIF-1α Is an Independent Prognostic Indicator in Kidney Cancer

PURPOSE

Clear cell renal cell carcinoma (ccRCC) is frequently associated with inactivation of the von Hippel-Lindau tumor suppressor, resulting in activation of HIF-1α and HIF-2α. The current paradigm, established using mechanistic cell-based studies, supports a tumor promoting role for HIF-2α, and a tumor suppressor role for HIF-1α. However, few studies have comprehensively examined the clinical relevance of this paradigm. Furthermore, the hypoxia-associated factor (HAF), which regulates the HIFs, has not been comprehensively evaluated in ccRCC.

EXPERIMENTAL DESIGN

To assess the involvement of HAF/HIFs in ccRCC, we analyzed their relationship to tumor grade/stage/outcome using tissue from 380 patients, and validated these associations using tissue from 72 additional patients and a further 57 patients treated with antiangiogenic therapy for associations with response. Further characterization was performed using single-cell mRNA sequencing (scRNA-seq), RNA-in situ hybridization (RNA-ISH), and IHC.

RESULTS

HIF-1α was primarily expressed in tumor-associated macrophages (TAMs), whereas HIF-2α and HAF were expressed primarily in tumor cells. TAM-associated HIF-1α was significantly associated with high tumor grade and increased metastasis and was independently associated with decreased overall survival. Furthermore, elevated TAM HIF-1α was significantly associated with resistance to antiangiogenic therapy. In contrast, high HAF or HIF-2α were associated with low grade, decreased metastasis, and increased overall survival. scRNA-seq, RNA-ISH, and Western blotting confirmed the expression of HIF-1α in M2-polarized CD163-expressing TAMs.

CONCLUSIONS

These findings highlight a potential role of TAM HIF-1α in ccRCC progression and support the reevaluation of HIF-1α as a therapeutic target and marker of disease progression.

Low Carbohydrate Diets in Men with Prostate Cancer May Reduce Risk of Cardiovascular Disease

Objectives

Both weight loss and low-carbohydrate diets (LCDs) have been shown to slow prostate cancer (PC) growth in animal models. Given the significant weight loss and purported metabolic benefits of LCDs to lower insulin and glucose (two key cancer growth factors), there is growing interest in using them in cancer patients. However, critics point to potentially increased cardiovascular disease (CVD) as a major risk. The objective of this study is to examine the effect of an LCD on estimated CVD risk within the context of randomized trials of LCD in PC patients.

Methods

Carbohydrate and Prostate Cancer (CAPS) 1 and CAPS2 studies were randomized clinical trials testing 6 mo. of an LCD vs. control (asked to make no diet changes) in overweight PC patients. CAPS1 included 34 men starting androgen deprivation therapy (ADT) and tested whether LCD prevents insulin resistance. CAPS2 included 45 men with recurrent PC after primary treatment and tested whether LCD slows PC growth. Primary results have been presented. In this post-hoc analysis, we calculated 10-year risk of CVD at baseline, 3 mo., and 6 mo. in each study based on a CVD risk model developed from the Framingham Heart Study. This score accounts for age, diabetes, smoking, treated and untreated systolic blood pressure and BMI. Comparisons between arms were made using t-tests. A mixed model was used to test longitudinal changes in CVD risk combining data from both studies but adjusting for study.

Results

In CAPS1, the 10-year estimated CVD risk was unchanged from baseline to 6 mo. at 29% in controls but decreased from 31% to 23% in the LCD arm (p = 0.23). In CAPS2, CVD risk increased from 34% to 35% in controls but decreased from 32% to 28% in the LCD arm (p = 0.005). When data from the two studies were combined, the LCD was associated with a lower 10-year estimated CVD risk vs. control over the study period (p &lt; 0.001).

Conclusions

Across two prospective randomized trials, an LCD in men with PC was associated with a lower estimated 10-year risk of CVD than control patients making no diet changes. These data support the safety of LCDs for men with PC. Given CVD is the number one cause of death in men with PC and pre-clinical data supporting anti-PC activity, further research on LCDs using long-term PC and CVD end-points is warranted.

Funding Sources

Atkins Foundation, American Urological Association, National Institute of Health/National Cancer Institute.

27-Hydroxycholesterol Impairs Plasma Membrane Lipid Raft Signaling as Evidenced by Inhibition of IL6-JAK-STAT3 Signaling in Prostate Cancer Cells

We recently reported that restoring the CYP27A1-27hydroxycholesterol axis had antitumor properties. Thus, we sought to determine the mechanism by which 27HC exerts its anti-prostate cancer effects. As cholesterol is a major component of membrane microdomains known as lipid rafts, which localize receptors and facilitate cellular signaling, we hypothesized 27HC would impair lipid rafts, using the IL6-JAK-STAT3 axis as a model given its prominent role in prostate cancer. As revealed by single molecule imaging of DU145 prostate cancer cells, 27HC treatment significantly reduced detected cholesterol density on the plasma membranes. Further, 27HC treatment of constitutively active STAT3 DU145 prostate cancer cells reduced STAT3 activation and slowed tumor growth in vitro and in vivo. 27HC also blocked IL6-mediated STAT3 phosphorylation in nonconstitutively active STAT3 cells. Mechanistically, 27HC reduced STAT3 homodimerization, nuclear translocation, and decreased STAT3 DNA occupancy at target gene promoters. Combined treatment with 27HC and STAT3 targeting molecules had additive and synergistic effects on proliferation and migration, respectively. Hallmark IL6-JAK-STAT gene signatures positively correlated with CYP27A1 gene expression in a large set of human metastatic castrate-resistant prostate cancers and in an aggressive prostate cancer subtype. This suggests STAT3 activation may be a resistance mechanism for aggressive prostate cancers that retain CYP27A1 expression. In summary, our study establishes a key mechanism by which 27HC inhibits prostate cancer by disrupting lipid rafts and blocking STAT3 activation. IMPLICATIONS: Collectively, these data show that modulation of intracellular cholesterol by 27HC can inhibit IL6-JAK-STAT signaling and may synergize with STAT3-targeted compounds.

A Low Glycemic Index Diet Slows Prostate Cancer Growth (P05-018-19)

Objectives

Carbohydrates are the main source of energy in older adults in the US. Moreover, they increase insulin and insulin-like growth factor-1 (IGF1), which are implicated in tumor growth by increasing cell survival. Previously, we found low carbohydrate (LC) diets slow prostate cancer (PC) growth and increase survival vs. a Western diet (WD) in mice. However, long-term adherence to a LC diet can be difficult for cancer patients. Thus, we aimed to determine whether modifying carbohydrate quality without changing quantity could result in the same outcome as when quantity is reduced. Carbohydrate quality was based on a glycemic index (GI), which indicates how carbohydrates affect blood glucose levels. Low GI carbohydrates are absorbed more slowly and result in a lower and slower increase in glucose levels and insulin demand than high GI carbohydrates. We hypothesized that high carbohydrate intake but with a low GI would slow PC growth, by reducing insulin levels.

Methods

A xenograft mice study compared the effect on PC growth of 3 diets: HiGI WD (48% carbohydrate: sucrose), HiGI LC (20% carbohydrate: sucrose), and LoGI WD (48% carbohydrate: amylose, amylopectin, maltodextrin). Male SCID mice were fed an ad lib HiGI WD. At day 14, they were injected with 5 × 105 LAPC-4 cells. When tumors reached ∼200 mm3, mice were single-housed and randomized to their diets (n = 33/group). Mice were pair-fed to ensure all had the same weight throughout the study. Tumor volume and body weight were measured 2X per week. Body composition was determined by Echo-MRI. The outcomes of the study were tumor volume, survival, glucose, insulin, IGF-1 and IGFBP-3 levels, and tumor tissue analysis.

Results

LoGI WD mice had lower tumor volumes, insulin, IGF1, and IGF1: IGFBP3 ratio, and higher IGF-BP3 levels, than the other two groups. Blood glucose was similar across arms. Even though body weight was similar across arms, LoGI WD mice had lower body fat. In a meal tolerance test, glucose was higher in HiGI WD mice with comparable results between the other two diets.

Conclusions

Feeding mice a low GI diet delayed PC growth and decreased serum insulin, IGF1 and IGF1: IGFBP3 ratios vs. a high GI diet. These data suggest carbohydrate quality is important for PC growth. Whether a low-carbohydrate and low GI diet would have additive benefits remains to be tested.

Funding Sources

American Institute for Cancer Research.

Prediction of acute coronary syndromes by urinary proteome analysis

Identification of individuals who are at risk of suffering from acute coronary syndromes (ACS) may allow to introduce preventative measures. We aimed to identify ACS-related urinary peptides, that combined as a pattern can be used as prognostic biomarker. Proteomic data of 252 individuals enrolled in four prospective studies from Australia, Europe and North America were analyzed. 126 of these had suffered from ACS within a period of up to 5 years post urine sampling (cases). Proteomic analysis of 84 cases and 84 matched controls resulted in the discovery of 75 ACS-related urinary peptides. Combining these to a peptide pattern, we established a prognostic biomarker named Acute Coronary Syndrome Predictor 75 (ACSP75). ACSP75 demonstrated reasonable prognostic discrimination (c-statistic = 0.664), which was similar to Framingham risk scoring (c-statistics = 0.644) in a validation cohort of 42 cases and 42 controls. However, generating by a composite algorithm named Acute Coronary Syndrome Composite Predictor (ACSCP), combining the biomarker pattern ACSP75 with the previously established urinary proteomic biomarker CAD238 characterizing coronary artery disease as the underlying aetiology, and age as a risk factor, further improved discrimination (c-statistic = 0.751) resulting in an added prognostic value over Framingham risk scoring expressed by an integrated discrimination improvement of 0.273 ± 0.048 (P < 0.0001) and net reclassification improvement of 0.405 ± 0.113 (P = 0.0007). In conclusion, we demonstrate that urinary peptide biomarkers have the potential to predict future ACS events in asymptomatic patients. Further large scale studies are warranted to determine the role of urinary biomarkers in clinical practice.