Associations of early-life and adult anthropometric measures with the expression of stem cell markers CD44, CD24, and ALDH1A1 in women with benign breast biopsies

BACKGROUND

According to the stem cell hypothesis, breast carcinogenesis may be related to the breast stem cell pool size. However, little is known about associations of breast cancer risk factors, such as anthropometric measures, with the expression of stem cell markers in non-cancerous breast tissue.

METHODS

The analysis included 414 women with biopsy-confirmed benign breast disease (BBD) in the Nurses' Health Study (NHS) and NHSII. Birthweight, weight at age 18, current weight, and current height were reported via self-administered questionnaire. Immunohistochemical staining of stem cell markers (CD44, CD24, ALDH1A1) in histopathologically normal epithelial and stromal breast tissue was quantified with an automated computational image analysis system. Linear regression was used to examine the associations of early-life and adult anthropometric measures with log-transformed stem cell marker expression, adjusting for potential confounders.

RESULTS

Birthweight (≥10.0 vs. <5.5 lbs: β [95% CI]=4.29 [1.02, 7.56]; p-trend=0.001 in stroma) and adult height (≥67.0 vs. <63.0 inch: 0.86 [0.14, 1.58]; p-trend=0.02 in epithelium and stroma combined) were positively associated with CD44 expression. Childhood body fatness was inversely (p-trend=0.03) and adult height was positively associated with CD24 expression in combined stroma and epithelium (p-trend=0.03).

CONCLUSION

Our data suggest that anthropometric measures, such as birthweight, adult height, and childhood body fatness, may be associated with the stem cell expression among women with BBD.

IMPACT

Anthropometric measures, such as birthweight, height, and childhood body fatness, may have long-term impacts on stem cell population in the breast.

CD24 negativity reprograms mitochondrial metabolism to PPARα and NF-κB-driven fatty acid β-oxidation in triple-negative breast cancer

CD24 is a well-characterized breast cancer (BC) stem cell (BCSC) marker. Primary breast tumor cells having CD24-negativity together with CD44-positivity is known to maintain high metastatic potential. However, the functional role of CD24 gene in triple-negative BC (TNBC), an aggressive subtype of BC, is not well understood. While the significance of CD24 in regulating immune pathways is well recognized in previous studies, the significance of CD24 low expression in onco-signaling and metabolic rewiring is largely unknown. Using CD24 knock-down and over-expression TNBC models, our in vitro and in vivo analysis suggest that CD24 is a tumor suppressor in metastatic TNBC. Comprehensive in silico gene expression analysis of breast tumors followed by lipidomic and metabolomic analyses of CD24-modulated cells revealed that CD24 negativity induces mitochondrial oxidative phosphorylation and reprograms TNBC metabolism toward the fatty acid beta-oxidation (FAO) pathway. CD24 silencing activates PPARα-mediated regulation of FAO in TNBC cells. Further analysis using reverse-phase protein array and its validation using CD24-modulated TNBC cells and xenograft models nominated CD24-NF-κB-CPT1A signaling pathway as the central regulatory mechanism of CD24-mediated FAO activity. Overall, our study proposes a novel role of CD24 in metabolic reprogramming that can open new avenues for the treatment strategies for patients with metastatic TNBC.

The MUC1-HIF-1α signaling axis regulates pancreatic cancer pathogenesis through polyamine metabolism remodeling

Dysregulation of polyamine metabolism has been implicated in cancer initiation and progression; however, the mechanism of polyamine dysregulation in cancer is not fully understood. In this study, we investigated the role of MUC1, a mucin protein overexpressed in pancreatic cancer, in regulating polyamine metabolism. Utilizing pancreatic cancer patient data, we noted a positive correlation between MUC1 expression and the expression of key polyamine metabolism pathway genes. Functional studies revealed that knockdown of spermidine/spermine N1-acetyltransferase 1 (SAT1), a key enzyme involved in polyamine catabolism, attenuated the oncogenic functions of MUC1, including cell survival and proliferation. We further identified a regulatory axis whereby MUC1 stabilized hypoxia-inducible factor (HIF-1α), leading to increased SAT1 expression, which in turn induced carbon flux into the tricarboxylic acid cycle. MUC1-mediated stabilization of HIF-1α enhanced the promoter occupancy of the latter on SAT1 promoter and corresponding transcriptional activation of SAT1, which could be abrogated by pharmacological inhibition of HIF-1α or CRISPR/Cas9-mediated knockout of HIF1A. MUC1 knockdown caused a significant reduction in the levels of SAT1-generated metabolites, N1-acetylspermidine and N8-acetylspermidine. Given the known role of MUC1 in therapy resistance, we also investigated whether inhibiting SAT1 would enhance the efficacy of FOLFIRINOX chemotherapy. By utilizing organoid and orthotopic pancreatic cancer mouse models, we observed that targeting SAT1 with pentamidine improved the efficacy of FOLFIRINOX, suggesting that the combination may represent a promising therapeutic strategy against pancreatic cancer. This study provides insights into the interplay between MUC1 and polyamine metabolism, offering potential avenues for the development of treatments against pancreatic cancer.

Cancer-associated fibroblast-derived acetate promotes pancreatic cancer development by altering polyamine metabolism via the ACSS2-SP1-SAT1 axis

The ability of tumour cells to thrive in harsh microenvironments depends on the utilization of nutrients available in the milieu. Here we show that pancreatic cancer-associated fibroblasts (CAFs) regulate tumour cell metabolism through the secretion of acetate, which can be blocked by silencing ATP citrate lyase (ACLY) in CAFs. We further show that acetyl-CoA synthetase short-chain family member 2 (ACSS2) channels the exogenous acetate to regulate the dynamic cancer epigenome and transcriptome, thereby facilitating cancer cell survival in an acidic microenvironment. Comparative H3K27ac ChIP-seq and RNA-seq analyses revealed alterations in polyamine homeostasis through regulation of SAT1 gene expression and enrichment of the SP1-responsive signature. We identified acetate/ACSS2-mediated acetylation of SP1 at the lysine 19 residue that increased SP1 protein stability and transcriptional activity. Genetic or pharmacologic inhibition of the ACSS2-SP1-SAT1 axis diminished the tumour burden in mouse models. These results reveal that the metabolic flexibility imparted by the stroma-derived acetate enabled cancer cell survival under acidosis via the ACSS2-SP1-SAT1 axis.

Associations of reproductive breast cancer risk factors with expression of stem cell markers in benign breast tissue

Background

We investigated the associations of reproductive factors known to influence breast cancer risk with the expression of breast stem cell markers CD44, CD24, and ALDH1A1 in benign breast biopsy samples.

Methods

We included 439 cancer-free women with biopsy-confirmed benign breast disease within the Nurses' Health Study (NHS) and NHSII. The data on reproductive and other breast cancer risk factors were obtained from biennial questionnaires. Immunohistochemistry (IHC) was performed on tissue microarrays. For each core, the IHC expression was assessed using a semi-automated platform and expressed as % of cells that stained positive for a specific marker out of the total cell count. Generalized linear regression was used to examine the associations of reproductive factors with a log-transformed expression of each marker (in epithelium and stroma), adjusted for other breast cancer risk factors.

Results

In multivariate analysis, the time between menarche and age at first birth was inversely associated with CD44 in epithelium (β per 5 years = -0.38, 95% CI -0.69; -0.06). Age at first birth and the time between menarche and age at first birth were inversely associated with ALDH1A1 (stroma: β per 5 years = -0.43, 95% CI -0.76; -0.10 and β = -0.47, 95% CI -0.79; -0.15, respectively; epithelium: β = -0.15, 95% CI -0.30; -0.01 and β = -0.17, 95% CI -0.30; -0.03, respectively). Time since last pregnancy was inversely associated with stromal ALDH1A1 (β per 5 years = -0.55, 95% CI -0.98; -0.11). No associations were found for CD24. The observed associations were similar in premenopausal women. In postmenopausal women, lifetime duration of breastfeeding was inversely associated with stromal ALDH1A1 expression (β for ≥24 vs. 0 to <1 months = -2.24, 95% CI 3.96; -0.51, p-trend = 0.01).

Conclusion

Early-life reproductive factors may influence CD44 and ALDH1A1 expression in benign breast tissue.

Vitamin B6 Competition in the Tumor Microenvironment Hampers Antitumor Functions of NK Cells

Nutritional factors play crucial roles in immune responses. The tumor-caused nutritional deficiencies are known to affect antitumor immunity. Here, we demonstrate that pancreatic ductal adenocarcinoma (PDAC) cells can suppress NK-cell cytotoxicity by restricting the accessibility of vitamin B6 (VB6). PDAC cells actively consume VB6 to support one-carbon metabolism, and thus tumor cell growth, causing VB6 deprivation in the tumor microenvironment. In comparison, NK cells require VB6 for intracellular glycogen breakdown, which serves as a critical energy source for NK-cell activation. VB6 supplementation in combination with one-carbon metabolism blockage effectively diminishes tumor burden in vivo. Our results expand the understanding of the critical role of micronutrients in regulating cancer progression and antitumor immunity, and open new avenues for developing novel therapeutic strategies against PDAC.

SIGNIFICANCE

The nutrient competition among the different tumor microenvironment components drives tumor growth, immune tolerance, and therapeutic resistance. PDAC cells demand a high amount of VB6, thus competitively causing NK-cell dysfunction. Supplying VB6 with blocking VB6-dependent one-carbon metabolism amplifies the NK-cell antitumor immunity and inhibits tumor growth in PDAC models. This article is featured in Selected Articles from This Issue, p. 5.

Associations of stem cell markers in benign breast tissue with subsequent breast cancer risk

We examined associations of stem cell markers CD44, CD24, and ALDH1A1 in benign breast biopsy samples with subsequent breast cancer (BCa) risk and explored if these associations were mediated by mammographic breast density (MBD). We included 101 BCa cases/375 controls, all with previous biopsy-confirmed benign breast disease (BBD) within the Nurses' Health Study (NHS) and NHSII. The data on BCa risk factors were obtained from biennial questionnaires. MBD was assessed with computer-assisted techniques. Immunohistochemistry (IHC) was done on BBD tissue microarrays. For each core, the IHC expression was assessed using a semi-automated method, and expressed as % of cells that stained positive for a specific marker out of the total cell count. Logistic regression was used to examine the associations of each marker's expression of each (in epithelium and stroma) with BCa risk, adjusted for risk factors. Stromal CD44 expression was inversely associated with BCa risk (OR for ≥10% vs. <10%=0.58, 95% CI 0.34, 1.00). Combined stromal + epithelial CD24 expression was inversely associated with BCa risk (>50% vs. 0-10% OR=0.17, 95% CI 0.04-0.81, p-trend =0.03). Stromal CD24 and ALDH1A1 as well as epithelial expression of any of the three markers were not associated with BCa risk. In a smaller subset of women with available MBD, these observed associations did not appear to be mediated by MBD. Our findings suggest inverse associations of CD44 in stroma and combined stromal + epithelial CD24 with BCa risk. Future studies are warranted to confirm our findings and to examine these associations by BBD subtype.

PTGES Expression Is Associated with Metabolic and Immune Reprogramming in Pancreatic Ductal Adenocarcinoma

Metabolic reprogramming is an established hallmark of multiple cancers, including pancreatic cancer. Dysregulated metabolism is utilized by cancer cells for tumor progression, metastasis, immune microenvironment remodeling, and therapeutic resistance. Prostaglandin metabolites have been shown to be critical for inflammation and tumorigenesis. While the functional role of prostaglandin E2 metabolite has been extensively studied, there is a limited understanding of the PTGES enzyme in pancreatic cancer. Here, we investigated the relationship between expression of prostaglandin E synthase (PTGES) isoforms and the pathogenesis and regulation of pancreatic cancer. Our analysis identified higher expression of PTGES in pancreatic tumors compared to normal pancreatic tissues, suggesting an oncogenic function. Only PTGES1 expression was significantly correlated with worse prognosis of pancreatic cancer patients. Further, utilizing cancer genome atlas data, PTGES was found to be positively correlated with epithelial-mesenchymal transition, metabolic pathways, mucin oncogenic proteins, and immune pathways in cancer cells. PTGES expression was also correlated with higher mutational burden in key driver genes, such as TP53 and KRAS. Furthermore, our analysis indicated that the oncogenic pathway controlled by PTGES1 could be regulated via DNA methylation-dependent epigenetic mechanisms. Notably, the glycolysis pathway was positively correlated with PTGES and may fuel cancer cell growth. PTGES expression was also associated with downregulation of the MHC pathway and negatively correlated with CD8+ T cell activation markers. In summary, our study established an association of PTGES expression with pancreatic cancer metabolism and the immune microenvironment.

Abstract P6-11-01: Scaffold attachment factor B1 modulates cholesterol pathways in triple-negative breast cancer

Historically known as a tumor suppressor by estrogen receptor (ER) co-repression in breast cancer (BC), the matrix binding protein Scaffold Attachment Factor B1 (SAFB) binds scaffold or matrix attachment region DNA elements (S/MAR DNA) in eukaryotic DNA. SAFB1 plays a role in cellular stress response, DNA repair, differentiation, and apoptosis. SAFB loss in ER-independent BC and pancreatic cancer (PC) patients resulted in poor survival rates, hinting at the role of SAFB1 as a tumor suppressor. To understand the tumor suppressive mechanism of SAFB1, we performed shRNA-mediated knockdown (KD) of SAFB in PC cell lines and triple-negative breast cancer (TNBC) cells, an aggressive subgroup of BC. Analysis of onco-properties showed an increase in clonogenicity potential and cell proliferation in SAFB KDs in both PDACs and TNBCs cells. Further, RNA-Seq analysis of SAFB KDs in the TNBC cell line revealed activation of the mevalonate (MVA) pathway and the resulting cholesterol biosynthesis as the key metabolic change. Both pancreatic ductal adenocarcinoma (PDACs) and TNBC exhibited higher levels of MVA pathway gene expression upon loss of SAFB. Sterol regulatory element binding proteins (SREBP) 1 and 2 dictate cholesterol biosynthesis, and SREBP2 promotes tumor properties via the MVA pathway. Molecular and metabolic analysis of SAFB KD TNBC showed an increase in lipid droplets and SREBP2 maturation. Using Chromatin Immunoprecipitation and quantitative real-time PCR (ChIP-qPCR) in TNBC we demonstrate the direct binding of SAFB to the SREBP2 promoter region. In addition, byproducts of the MVA pathway have been shown to activate YAP/TAZ-dependent tissue homeostasis and tumorigenesis. We also observed increased YAP1 mRNA levels and decreased YAP1 (Ser127) phosphorylation with SAFB loss in TNBC, explaining the aggressive tumorigenicity gained with SAFB loss. Our study thus far suggests SAFB has overt control over the SREBP2-MVA-YAP1 pathway, and loss of SAFB results in an enhanced tumor phenotype.

Citation Format: Meron Ghidey, Divya Murthy, Sukjin Yang, Songyeon Ahn, Jun Hyoung Park, Benny Kaipparettu. Scaffold attachment factor B1 modulates cholesterol pathways in triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-11-01.

Reliability of CD44, CD24, and ALDH1A1 immunohistochemical staining: Pathologist assessment compared to quantitative image analysis

Background

The data on the expression of stem cell markers CD44, CD24, and ALDH1A1 in the breast tissue of cancer-free women is very limited and no previous studies have explored the agreement between pathologist and computational assessments of these markers. We compared the immunohistochemical (IHC) expression assessment for CD44, CD24, and ALDH1A1 by an expert pathologist with the automated image analysis results and assessed the homogeneity of the markers across multiple cores pertaining to each woman.

Methods

We included 81 cancer-free women (399 cores) with biopsy-confirmed benign breast disease in the Nurses' Health Study (NHS) and NHSII cohorts. IHC was conducted with commercial antibodies [CD44 (Dako, Santa Clara, CA, USA) 1:25 dilution; CD24 (Invitrogen, Waltham, MA, USA) 1:200 dilution and ALDH1A1 (Abcam, Cambridge, United Kingdom) 1:300 dilution]. For each core, the percent positivity was quantified by the pathologist and Definiens Tissue Studio. Correlations between pathologist and computational scores were evaluated with Spearman correlation (for categorical positivity: 0, >0-<1, 1-10, >10-50, and >50%) and sensitivity/specificity (for binary positivity defined with 1 and 10% cut-offs), using the pathologist scores as the gold standard. Expression homogeneity was examined with intra-class correlation (ICC). Analyses were stratified by core [normal terminal duct-lobular units (TDLUs), benign lesions] and tissue type (epithelium, stroma).

Results

Spearman correlation between pathologist and Definiens ranged between 0.40-0.64 for stroma and 0.66-0.68 for epithelium in normal TDLUs cores and between 0.24-0.60 for stroma and 0.61-0.64 for epithelium in benign lesions. For stroma, sensitivity and specificity ranged between 0.92-0.95 and 0.24-0.60, respectively, with 1% cut-off and between 0.43-0.88 and 0.73-0.85, respectively, with 10% cut-off. For epithelium, 10% cut-off resulted in better estimates for both sensitivity and specificity. ICC between the cores was strongest for CD44 for both stroma and epithelium in normal TDLUs cores and benign lesions (range 0.74-0.80). ICC for CD24 and ALDH1A ranged between 0.42-0.63 and 0.44-0.55, respectively.

Conclusion

Our findings show that computational assessments for CD44, CD24, and ALDH1A1 exhibit variable correlations with manual assessment. These findings support the use of computational platforms for IHC evaluation of stem cell markers in large-scale epidemiologic studies. Pilot studies maybe also needed to determine appropriate cut-offs for defining staining positivity.

MnTE-2-PyP protects fibroblast mitochondria from hyperglycemia and radiation exposure

Radiation is a common anticancer therapy for prostate cancer, which transforms tumor-associated normal fibroblasts to myofibroblasts, resulting in fibrosis. Oxidative stress caused by radiation-mediated mitochondrial damage is one of the major contributors to fibrosis. As diabetics are oxidatively stressed, radiation-mediated reactive oxygen species cause severe treatment failure, treatment-related side effects, and significantly reduced survival for diabetic prostate cancer patients as compared to non-diabetic prostate cancer patients. Hyperglycemia and enhanced mitochondrial damage significantly contribute to oxidative damage and disease progression after radiation therapy among diabetic prostate cancer patients. Therefore, reduction of mitochondrial damage in normal prostate fibroblasts after radiation should improve the overall clinical state of diabetic prostate cancer patients. We previously reported that MnTE-2-PyP, a manganese porphyrin, reduces oxidative damage in irradiated hyperglycemic prostate fibroblasts by scavenging superoxide and activating NRF2. In the current study, we have investigated the potential role of MnTE-2-PyP to protect mitochondrial health in irradiated hyperglycemic prostate fibroblasts. This study revealed that hyperglycemia and radiation increased mitochondrial ROS via blocking the mitochondrial electron transport chain, altered mitochondrial dynamics, and reduced mitochondrial biogenesis. Increased mitochondrial damage preceeded an increase in myofibroblast differentiation. MnTE-2-PyP reduced myofibroblast differentiation, improved mitochondrial health by releasing the block on the mitochondrial electron transport chain, enhanced ATP production efficiency, and restored mitochondrial dynamics and metabolism in the irradiated-hyperglycemic prostate fibroblasts. Therefore, we are proposing that one of the mechanisms that MnTE-2-PyP protects prostate fibroblasts from irradiation and hyperglycemia-mediated damage is by protecting the mitochondrial health in diabetic prostate cancer patients.

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MnTE-2-PyP protects mitochondria from radiation and hyperglycemia-induced stress.

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MnTE-2-PyP reduced mitochondrial ROS by restoring the levels of OXPHOS complexes.

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MnTE-2-PyP increased the number of healthy mitochondria and enhanced ATP production efficiency.

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Mitochondrial protection by MnTE-2-PyP inhibits myofibroblast differentiation.

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MnTE-2-PyP treatment partly restores radiation-mediated metabolic changes.

Temporal analysis of melanogenesis identifies fatty acid metabolism as key skin pigment regulator

Therapeutic methods to modulate skin pigmentation has important implications for skin cancer prevention and for treating cutaneous hyperpigmentary conditions. Towards defining new potential targets, we followed temporal dynamics of melanogenesis using a cell-autonomous pigmentation model. Our study elucidates 3 dominant phases of synchronized metabolic and transcriptional reprogramming. The melanogenic trigger is associated with high MITF levels along with rapid uptake of glucose. The transition to pigmented state is accompanied by increased glucose channelisation to anabolic pathways that support melanosome biogenesis. SREBF1-mediated up-regulation of fatty acid synthesis results in a transient accumulation of lipid droplets and enhancement of fatty acids oxidation through mitochondrial respiration. While this heightened bioenergetic activity is important to sustain melanogenesis, it impairs mitochondria lately, shifting the metabolism towards glycolysis. This recovery phase is accompanied by activation of the NRF2 detoxication pathway. Finally, we show that inhibitors of lipid metabolism can resolve hyperpigmentary conditions in a guinea pig UV-tanning model. Our study reveals rewiring of the metabolic circuit during melanogenesis, and fatty acid metabolism as a potential therapeutic target in a variety of cutaneous diseases manifesting hyperpigmentary phenotype.

Temporal analysis of melanogenesis, based on transcriptomic and metabolomic signatures, reveals fatty acid metabolism as a crucial mediator of the transition between pigmentation phases. Inhibitors of the fatty acid pathway could represent a new target for modulating pigmentation.

CD73 induces GM-CSF/MDSC-mediated suppression of T cells to accelerate pancreatic cancer pathogenesis

Metabolic alterations regulate cancer aggressiveness and immune responses. Given the poor response of pancreatic ductal adenocarcinoma (PDAC) to conventional immunotherapies, we investigated the link between metabolic alterations and immunosuppression. Our metabolic enzyme screen indicated that elevated expression of CD73, an ecto-5'-nucleotidase that generates adenosine, correlates with increased aggressiveness. Correspondingly, we observed increased interstitial adenosine levels in tumors from spontaneous PDAC mouse models. Diminishing CD73 by genetic manipulations ablated in vivo tumor growth, and decreased myeloid-derived suppressor cells (MDSC) in orthotopic mouse models of PDAC. A high-throughput cytokine profiling demonstrated decreased GM-CSF in mice implanted with CD73 knockdowns. Furthermore, we noted increased IFN-γ expression by intratumoral CD4⁺ and CD8⁺ T cells in pancreatic tumors with CD73 knockdowns. Depletion of CD4⁺ T cells, but not CD8⁺ T cells abrogated the beneficial effects of decreased CD73. We also observed that splenic MDSCs from Nt5e knockdown tumor-bearing mice were incompetent in suppressing T cell activation in the ex vivo assays. Replenishing GM-CSF restored tumor growth in Nt5e knockout tumors, which was reverted by MDSC depletion. Finally, anti-CD73 antibody treatment significantly improved gemcitabine efficacy in orthotopic models. Thus, targeting the adenosine axis presents a novel therapeutic opportunity for improving the anti-tumoral immune response against PDAC.

Metabolic Rewiring by Loss of Sirt5 Promotes Kras-Induced Pancreatic Cancer Progression

BACKGROUND & AIMS

SIRT5 plays pleiotropic roles via post-translational modifications, serving as a tumor suppressor, or an oncogene, in different tumors. However, the role SIRT5 plays in the initiation and progression of pancreatic ductal adenocarcinoma (PDAC) remains unknown.

METHODS

Published datasets and tissue arrays with SIRT5 staining were used to investigate the clinical relevance of SIRT5 in PDAC. Furthermore, to define the role of SIRT5 in the carcinogenesis of PDAC, we generated autochthonous mouse models with conditional Sirt5 knockout. Moreover, to examine the mechanistic role of SIRT5 in PDAC carcinogenesis, SIRT5 was knocked down in PDAC cell lines and organoids, followed by metabolomics and proteomics studies. A novel SIRT5 activator was used for therapeutic studies in organoids and patient-derived xenografts.

RESULTS

SIRT5 expression negatively regulated tumor cell proliferation and correlated with a favorable prognosis in patients with PDAC. Genetic ablation of Sirt5 in PDAC mouse models promoted acinar-to-ductal metaplasia, precursor lesions, and pancreatic tumorigenesis, resulting in poor survival. Mechanistically, SIRT5 loss enhanced glutamine and glutathione metabolism via acetylation-mediated activation of GOT1. A selective SIRT5 activator, MC3138, phenocopied the effects of SIRT5 overexpression and exhibited antitumor effects on human PDAC cells. MC3138 also diminished nucleotide pools, sensitizing human PDAC cell lines, organoids, and patient-derived xenografts to gemcitabine.

CONCLUSIONS

Collectively, we identify SIRT5 as a key tumor suppressor in PDAC, whose loss promotes tumorigenesis through increased noncanonic use of glutamine via GOT1, and that SIRT5 activation is a novel therapeutic strategy to target PDAC.

Associations of reproductive breast cancer risk factors with breast tissue composition

BACKGROUND

We investigated the associations of reproductive factors with the percentage of epithelium, stroma, and fat tissue in benign breast biopsy samples.

METHODS

This study included 983 cancer-free women with biopsy-confirmed benign breast disease (BBD) within the Nurses' Health Study and Nurses' Health Study II cohorts. The percentage of each tissue type (epithelium, stroma, and fat) was measured on whole-section images with a deep-learning technique. All tissue measures were log-transformed in all the analyses to improve normality. The data on reproductive variables and other breast cancer risk factors were obtained from biennial questionnaires. Generalized linear regression was used to examine the associations of reproductive factors with the percentage of tissue types, while adjusting for known breast cancer risk factors.

RESULTS

As compared to parous women, nulliparous women had a smaller percentage of epithelium (β = - 0.26, 95% confidence interval [CI] - 0.41, - 0.11) and fat (β = - 0.34, 95% CI - 0.54, - 0.13) and a greater percentage of stroma (β = 0.04, 95% CI 0.01, 0.08). Among parous women, the number of children was inversely associated with the percentage of stroma (β per child = - 0.01, 95% CI - 0.02, - 0.00). The duration of breastfeeding of ≥ 24 months was associated with a reduced proportion of fat (β = - 0.30, 95% CI - 0.54, - 0.06; p-trend = 0.04). In a separate analysis restricted to premenopausal women, older age at first birth was associated with a greater proportion of epithelium and a smaller proportion of stroma.

CONCLUSIONS

Our findings suggest that being nulliparous as well as having a fewer number of children (both positively associated with breast cancer risk) is associated with a smaller proportion of epithelium and a greater proportion of stroma, potentially suggesting the importance of epithelial-stromal interactions. Future studies are warranted to confirm our findings and to elucidate the underlying biological mechanisms.

Automated percent mammographic density, mammographic texture variation, and risk of breast cancer: a nested case-control study

Percent mammographic density (PMD) is a strong breast cancer risk factor, however, other mammographic features, such as V, the standard deviation (SD) of pixel intensity, may be associated with risk. We assessed whether PMD, automated PMD (APD), and V, yielded independent associations with breast cancer risk. We included 1900 breast cancer cases and 3921 matched controls from the Nurses' Health Study (NHS) and the NHSII. Using digitized film mammograms, we estimated PMD using a computer-assisted thresholding technique. APD and V were determined using an automated computer algorithm. We used logistic regression to generate odds ratios (ORs) and 95% confidence intervals (CIs). Median time from mammogram to diagnosis was 4.1 years (interquartile range: 1.6-6.8 years). PMD (OR per SD:1.52, 95% CI: 1.42, 1.63), APD (OR per SD:1.32, 95% CI: 1.24, 1.41), and V (OR per SD:1.32, 95% CI: 1.24, 1.40) were positively associated with breast cancer risk. Associations for APD were attenuated but remained statistically significant after mutual adjustment for PMD or V. Women in the highest quartile of both APD and V (OR vs Q1/Q1: 2.49, 95% CI: 2.02, 3.06), or PMD and V (OR vs Q1/Q1: 3.57, 95% CI: 2.79, 4.58) had increased breast cancer risk. An automated method of PMD assessment is feasible and yields similar, but somewhat weaker, estimates to a manual measure. PMD, APD and V are each independently, positively associated with breast cancer risk. Women with dense breasts and greater texture variation are at the highest relative risk of breast cancer.

SIRT1-NOX4 signaling axis regulates cancer cachexia

Approximately one third of cancer patients die due to complexities related to cachexia. However, the mechanisms of cachexia and the potential therapeutic interventions remain poorly studied. We observed a significant positive correlation between SIRT1 expression and muscle fiber cross-sectional area in pancreatic cancer patients. Rescuing Sirt1 expression by exogenous expression or pharmacological agents reverted cancer cell–induced myotube wasting in culture conditions and mouse models. RNA-seq and follow-up analyses showed cancer cell–mediated SIRT1 loss induced NF-κB signaling in cachectic muscles that enhanced the expression of FOXO transcription factors and NADPH oxidase 4 (Nox4), a key regulator of reactive oxygen species production. Additionally, we observed a negative correlation between NOX4 expression and skeletal muscle fiber cross-sectional area in pancreatic cancer patients. Knocking out Nox4 in skeletal muscles or pharmacological blockade of Nox4 activity abrogated tumor-induced cachexia in mice. Thus, we conclude that targeting the Sirt1–Nox4 axis in muscles is an effective therapeutic intervention for mitigating pancreatic cancer–induced cachexia.

Abstract PS7-90: Reproductive breast cancer risk factors and breast tissue composition on benign breast biopsies

Background: Reproductive factors related to childbearing are recognized as breast cancer risk factors. Whether any of these factors could influence adult breast tissue composition is unclear. We investigated the associations of reproductive factors with percentage of epithelium, stroma, and fat tissue in benign breast biopsy samples. Methods: This study included 983 cancer-free women with biopsy-confirmed benign breast disease (BBD) within the Nurses’ Health Study and Nurses’ Health Study II cohorts. Percentage of each tissue type (epithelium stroma, and fat) was measured on whole section images with a deep-learning technique. All tissue measures were log-transformed in all the analyses to improve normality. The data on reproductive variables and other breast cancer risk factors were obtained from biennial questionnaires. Generalized linear regression was used to examine the associations of reproductive factors (parity, age at first birth, breastfeeding, age at menarche and the duration of the interval between menarche and age at first birth) with percentage of tissue types, while adjusting for known breast cancer risk factors.Results: In this study of 983 cancer-free women, 299 (30.4%) had non-proliferative disease, 559 (56.9%) had proliferative disease without atypia, and 125 (12.7%) had atypical hyperplasia, consistent with previously reported distributions of these BBD subtypes. The average proportion of epithelium, stroma, and fat in our study sample was 9.1% (range 0.5-52.2%), 72.4% (range 23.6-99.0%), and 18.5% (range 0-71.3%), respectively. As compared to parous women, nulliparous women had a smaller percentage of epithelium (β= -0.26, 95% confidence interval [CI] -0.41, -0.11) and fat (β= -0.34, 95% CI -0.54, -0.13) and a greater percentage of stroma (β=0.04, 95% CI 0.01, 0.08). Among parous women, number of children was inversely associated with percentage of stroma (β per child= -0.01 (-0.02, -0.00). Duration of breastfeeding of ≥24 months was associated with a reduced proportion of fat (β= -0.30, 95% CI -0.54, -0.06; p-trend=0.04). In a separate analysis restricted to premenopausal women, being nulliparous was associated with a greater proportion of stroma (β=0.06, 95% CI 0.02, 0.10) and smaller proportion of epithelium (β= -0.22, 95% CI -0.38, -0.06) and fat (β= -0.32, 95% CI -0.56,

-0.08). Greater parity and older age at first birth were both associated with a greater proportion of epithelium (and a smaller proportion of stroma. The age at menarche and the duration of the interval between age at menarche and first birth were not associated with the proportion of any of the tissue types. Conclusions: Our findings suggest that reproductive factors with a protective effect on breast cancer risk may be associated with a greater proportion of epithelium and a smaller proportion of stroma, potentially suggesting importance of epithelial-stromal interactions. Future studies are warranted to confirm our findings and to elucidate the underlying biological mechanisms.

Citation Format: Lusine Yaghjyan, Rebecca J Austin-Datta, Hannah Oh, Yujing J Heng, Adithya D Vellal, Korsuk Sirinukunwattana, Gabrielle M Baker, Laura Collins, Divya Murthy, Bernard Rosner, Rulla M Tamimi. Reproductive breast cancer risk factors and breast tissue composition on benign breast biopsies [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-90.

Early-Life and Adult Adiposity, Adult Height, and Benign Breast Tissue Composition

BACKGROUND

Early-life and adult anthropometrics are associated with breast density and breast cancer risk. However, little is known about whether these factors also influence breast tissue composition beyond what is captured by breast density among women with benign breast disease (BBD).

METHODS

This analysis included 788 controls from a nested case-control study of breast cancer within the Nurses' Health Study BBD subcohorts. Body fatness at ages 5 and 10 years was recalled using a 9-level pictogram. Weight at age 18, current weight, and height were reported via questionnaires. A deep-learning image analysis was used to quantify the percentages of epithelial, fibrous stromal, and adipose tissue areas within BBD slides. We performed linear mixed models to estimate beta coefficients (β) and 95% confidence intervals (CI) for the relationships between anthropometrics and the log-transformed percentages of individual tissue type, adjusting for confounders.

RESULTS

Childhood body fatness (level ≥ 4.5 vs. 1), BMI at age 18 (≥23 vs. <19 kg/m²), and current adult BMI (≥30 vs. <21 kg/m²) were associated with higher proportions of adipose tissue [β (95% CI) = 0.34 (0.03, 0.65), 0.19 (-0.04-0.42), 0.40 (0.12, 0.68), respectively] and lower proportions of fibrous stromal tissue [-0.05 (-0.10, 0.002), -0.03 (-0.07, 0.003), -0.12 (-0.16, -0.07), respectively] during adulthood (all P _trend < 0.04). BMI at age 18 was also inversely associated with epithelial tissue (P _trend = 0.03). Adult height was not associated with any of the individual tissue types.

CONCLUSIONS

Our data suggest that body fatness has long-term impacts on breast tissue composition.

IMPACT

This study contributes to our understanding of the link between body fatness and breast cancer risk.See related commentary by Oskar et al., p. 590.

JNK signaling contributes to skeletal muscle wasting and protein turnover in pancreatic cancer cachexia

Cancer cachexia patients experience significant muscle wasting, which impairs the quality of life and treatment efficacy for patients. Skeletal muscle protein turnover is imparted by increased expression of ubiquitin-proteasome pathway components. Mitogen-activated protein kinases p38 and ERK have been shown to augment E3 ubiquitin ligase expression. Utilizing reverse-phase protein arrays, we identified pancreatic cancer cell-conditioned media-induced activation of JNK signaling in myotubes differentiated from C2C12 myoblasts. Inhibition of JNK signaling with SP600125 reduced cancer cell-conditioned media-induced myotube atrophy, myosin heavy chain protein turnover, and mRNA expression of cachexia-specific ubiquitin ligases Trim63 and Fbxo32. Furthermore, utilizing an orthotopic pancreatic cancer cachexia mouse model, we demonstrated that treatment of tumor-bearing mice with SP600125 improved longitudinal measurements of forelimb grip strength. Post-necropsy measurements demonstrated that SP600125 treatment rescued body weight, carcass weight, and gastrocnemius muscle weight loss without impacting tumor growth. JNK inhibitor treatment also rescued myofiber degeneration and reduced the muscle expression of Trim63 and Fbxo32. These data demonstrate that JNK signaling contributes to muscle wasting in cancer cachexia, and its inhibition has the potential to be utilized as an anti-cachectic therapy.

Abstract 5132: Lactic acidosis-mediated transcriptomic and metabolomic rewiring in pancreatic cancer cells

Tumor microenvironment plays a critical role in regulating tumor cell metabolism and progression. The tumor cells are constantly exposed to hypoxia, nutrient starvation, and extracellular acidification that contribute to tumor malignancy. These malignant cells exhibit Warburg effect by maintaining glycolytic phenotype even in the presence of oxygen and excrete lactate and protons via monocarboxylate transporters, and sodium-hydrogen antiporter 1 (NHE1) causing constant acidification of the tumor microenvironment. The tumor cells must thus adapt to acidosis to thrive in such hostile microenvironment. The purpose of the study is to identify the functional response of pancreatic cancer cells to the acidic tumor microenvironment. We performed integrated transcriptomic and metabolomic analyses to identify the existence of low pH-responsive transcriptional and metabolic regulators. Culturing the cells under low pH resulted in a reduction in cell growth and an increase in oxidative stress within the cells. RNA-seq-based transcriptomic analyses revealed that acidosis drives distinct gene expression patterns in PDAC cells with the expression of 499 and 496 genes up- and downregulated, respectively in PDAC cells. GSEA analyses of significantly modulated genes identified pathways including cell cycle, DNA repair, metabolic pathways, ABC transporters, glutathione metabolism, and genes involved in signaling cascades such as the inositide signaling pathway. As the transcriptomic analyses showed an enrichment of metabolic genes, intracellular metabolomic analyses revealed that chronic acidosis leads to a shift in cellular metabolism towards oxidative metabolism. Our studies demonstrate that while chronic acidosis in the tumor microenvironment leads to reduced proliferation and glycolysis in tumor cells, it also results in increased expression of genes involved in cellular migration, signaling pathways and switching to anaplerotic glutamine metabolism in response to an acidic tumor microenvironment. Overall, our studies demonstrate metabolic reprogramming in PDAC cells in response to low pH microenvironments creating a metabolic vulnerability that could be exploited for therapeutic targeting of pancreatic cancer.

Citation Format: Divya Murthy, Jaime Abrego, Ryan James King, Pankaj Kumar Singh. Lactic acidosis-mediated transcriptomic and metabolomic rewiring in pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5132.

Phosphoinositide 3-Kinase Signaling Pathway in Pancreatic Ductal Adenocarcinoma Progression, Pathogenesis, and Therapeutics

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy characterized by its sudden manifestation, rapid progression, poor prognosis, and limited therapeutic options. Genetic alterations in key signaling pathways found in early pancreatic lesions are pivotal for the development and progression of pancreatic intraepithelial neoplastic lesions into invasive carcinomas. More than 90% of PDAC tumors harbor driver mutations in K-Ras that activate various downstream effector-signaling pathways, including the phosphoinositide-3-kinase (PI3K) pathway. The PI3K pathway also responds to stimuli from various growth factor receptors present on the cancer cell surface that, in turn, modulate downstream signaling cascades. Thus, the inositide signaling acts as a central node in the complex cellular signaling networks to impact cancer cell growth, motility, metabolism, and survival. Also, recent publications highlight the importance of PI3K signaling in stromal cells, whereby PI3K signaling modifies the tumor microenvironment to dictate disease outcome. The high incidence of mutations in the PI3K signaling cascade, accompanied by activation of parallel signaling pathways, makes PI3K a promising candidate for drug therapy. In this review, we describe the role of PI3K signaling in pancreatic cancer development and progression. We also discuss the crosstalk between PI3K and other major cellular signaling cascades, and potential therapeutic opportunities for targeting pancreatic ductal adenocarcinoma.

Evaluating the Metabolic Impact of Hypoxia on Pancreatic Cancer Cells

Hypoxia is frequently observed in human cancers and induces global metabolic reprogramming that includes an increase in glucose uptake and glycolysis, alterations in NAD(P)H/NAD(P)⁺ and intracellular ATP levels, and increased utilization of glutamine as the major precursor for fatty acid synthesis. In this chapter, we describe in detail various physiological assays that have been adopted to study the metabolic shift propagated by exposure to hypoxic conditions in pancreatic cell culture model that includes glucose uptake, glutamine uptake, and lactate release by pancreatic cancer cell lines. We have also elaborated the assays to evaluate the ratio of NAD(P)H/NAD(P)⁺ and intracellular ATP estimation using the commercially available kit to assess the metabolic state of cancer cells.

MUC1 and HIF-1alpha Signaling Crosstalk Induces Anabolic Glucose Metabolism to Impart Gemcitabine Resistance to Pancreatic Cancer

Poor response to cancer therapy due to resistance remains a clinical challenge. The present study establishes a widely prevalent mechanism of resistance to gemcitabine in pancreatic cancer, whereby increased glycolytic flux leads to glucose addiction in cancer cells and a corresponding increase in pyrimidine biosynthesis to enhance the intrinsic levels of deoxycytidine triphosphate (dCTP). Increased levels of dCTP diminish the effective levels of gemcitabine through molecular competition. We also demonstrate that MUC1-regulated stabilization of hypoxia inducible factor-1α (HIF-1α) mediates such metabolic reprogramming. Targeting HIF-1α or de novo pyrimidine biosynthesis, in combination with gemcitabine, strongly diminishes tumor burden. Finally, reduced expression of TKT and CTPS, which regulate flux into pyrimidine biosynthesis, correlates with better prognosis in pancreatic cancer patients on fluoropyrimidine analogs.

Classical autophagy proteins LC3B and ATG4B facilitate melanosome movement on cytoskeletal tracks

Macroautophagy/autophagy is a dynamic and inducible catabolic process that responds to a variety of hormonal and environmental cues. Recent studies highlight the interplay of this central pathway in a variety of pathophysiological diseases. Although defective autophagy is implicated in melanocyte proliferation and pigmentary disorders, the mechanistic relationship between the 2 pathways has not been elucidated. In this study, we show that autophagic proteins LC3B and ATG4B mediate melanosome trafficking on cytoskeletal tracks. While studying melanogenesis, we observed spatial segregation of LC3B-labeled melanosomes with preferential absence at the dendritic ends of melanocytes. This LC3B labeling of melanosomes did not impact the steady-state levels of these organelles but instead facilitated their intracellular positioning. Melanosomes primarily traverse on microtubule and actin cytoskeletal tracks and our studies reveal that LC3B enables the assembly of microtubule translocon complex. At the microtubule-actin crossover junction, ATG4B detaches LC3B from melanosomal membranes by enzymatic delipidation. Further, by live-imaging we show that melanosomes transferred to keratinocytes lack melanocyte-specific LC3B. Our study thus elucidates a new role for autophagy proteins in directing melanosome movement and reveal the unconventional use of these proteins in cellular trafficking pathways. Such crosstalk between the central cellular function and housekeeping pathway may be a crucial mechanism to balance melanocyte bioenergetics and homeostasis.

GOT1-mediated anaplerotic glutamine metabolism regulates chronic acidosis stress in pancreatic cancer cells

The increased rate of glycolysis and reduced oxidative metabolism are the principal biochemical phenotypes observed in pancreatic ductal adenocarcinoma (PDAC) that lead to the development of an acidic tumor microenvironment. The pH of most epithelial cell-derived tumors is reported to be lower than that of plasma. However, little is known regarding the physiology and metabolism of cancer cells enduring chronic acidosis. Here, we cultured PDAC cells in chronic acidosis (pH 6.9-7.0) and observed that cells cultured in low pH had reduced clonogenic capacity. However, our physiological and metabolomics analysis showed that cells in low pH deviate from glycolytic metabolism and rely more on oxidative metabolism. The increased expression of the transaminase enzyme GOT1 fuels oxidative metabolism of cells cultured in low pH by enhancing the non-canonical glutamine metabolic pathway. Survival in low pH is reduced upon depletion of GOT1 due to increased intracellular ROS levels. Thus, GOT1 plays an important role in energy metabolism and ROS balance in chronic acidosis stress. Our studies suggest that targeting anaplerotic glutamine metabolism may serve as an important therapeutic target in PDAC.

Racial disparity in metabolic regulation of cancer

Genetic mutations and metabolic reprogramming are two key hallmarks of cancer, required for proliferation, invasion, and metastasis of the disease. While genetic mutations, whether inherited or acquired, are critical for the initiation of tumor development, metabolic reprogramming is an effector mechanism imperative for adaptational transition during the progression of cancer. Recent findings in the literature emphasize the significance of molecular cross-talk between these two cellular processes in regulating signaling and differentiation of cancer cells. Genome-wide sequencing analyses of cancer genomes have highlighted the association of various genic mutations in predicting cancer risk and survival. Oncogenic mutational frequency is heterogeneously distributed among various cancer types in different populations, resulting in varying susceptibility to cancer risk. In this review, we explore and discuss the role of genetic mutations in metabolic enzymes and metabolic oncoregulators to stratify cancer risk in persons of different racial backgrounds.

The Molecular Mechanism Underlying Recruitment and Insertion of Lipid-Anchored LC3 Protein into Membranes

Lipid modification of cytoplasmic proteins initiates membrane engagement that triggers diverse cellular processes. Despite the abundance of lipidated proteins in the human proteome, the key determinants underlying membrane recognition and insertion are poorly understood. Here, we define the course of spontaneous membrane insertion of LC3 protein modified with phosphatidylethanolamine using multiple coarse-grain simulations. The partitioning of the lipid anchor chains proceeds through a concerted process, with its two acyl chains inserting one after the other. Concurrently, a conformational rearrangement involving the α-helix III of LC3, especially in the three basic residues Lys65, Arg68, and Arg69, ensures stable insertion of the phosphatidylethanolamine anchor into membranes. Mutational studies validate the crucial role of these residues, and further live-cell imaging analysis shows a substantial reduction in the formation of autophagic vesicles for the mutant proteins. Our study captures the process of water-favored LC3 protein recruitment to the membrane and thus opens, to our knowledge, new avenues to explore the cellular dynamics underlying vesicular trafficking.

Network, nodes and nexus: systems approach to multitarget therapeutics

Systems biology is revealing multiple layers of regulatory networks that manifest spatiotemporal variations. Since genes and environment also influence the emergent property of a cell, the biological output requires dynamic understanding of various molecular circuitries. The metabolic networks continually adapt and evolve to cope with the changing milieu of the system, which could also include infection by another organism. Such perturbations of the functional networks can result in disease phenotypes, for instance tuberculosis and cancer. In order to develop effective therapeutics, it is important to determine the disease progression profiles of complex disorders that can reveal dynamic aspects and to develop mutitarget systemic therapies that can help overcome pathway adaptations and redundancy.

Immunoglobulin G4-associated cholangitis mimicking cholangiocarcinoma in a young boy

Autoimmune pancreatitis is a rare form of chronic pancreatitis, which commonly mimics pancreatic carcinoma. Immunoglobulin G4-associated cholangitis (IAC) is a rare type of autoimmune pancreatitis associated with bile duct involvement, which can present with or without pancreatic involvement. Usually, the bile duct involvement is in the form of multiple intra-and extra-hepatic strictures mimicking primary sclerosing cholangitis. Rarely, there can be an isolated stricture which mimics cholangiocarcinoma. Differentiating these from cholangiocarcinoma, though extremely difficult, is of critical importance since it can be treated without surgical intervention. Most cases with rare presentation mimicking cholangiocarcinoma have been reported in elderly patients. We present one such rare presentation of autoimmune pancreatitis in a young 13-year-old patient in whom hepaticojejunostomy was done for a hilar stricture, which later turned out to be related to IAC. To our knowledge this is the first reported case of its kind from India.