Staphylococcus aureus induces drug resistance in cancer T cells in Sézary syndrome

ABSTRACT

Patients with Sézary syndrome (SS), a leukemic variant of cutaneous T-cell lymphoma (CTCL), are prone to Staphylococcus aureus infections and have a poor prognosis due to treatment resistance. Here, we report that S aureus and staphylococcal enterotoxins (SE) induce drug resistance in malignant T cells against therapeutics commonly used in CTCL. Supernatant from patient-derived, SE-producing S aureus and recombinant SE significantly inhibit cell death induced by histone deacetylase (HDAC) inhibitor romidepsin in primary malignant T cells from patients with SS. Bacterial killing by engineered, bacteriophage-derived, S aureus-specific endolysin (XZ.700) abrogates the effect of S aureus supernatant. Similarly, mutations in major histocompatibility complex (MHC) class II binding sites of SE type A (SEA) and anti-SEA antibody block induction of resistance. Importantly, SE also triggers resistance to other HDAC inhibitors (vorinostat and resminostat) and chemotherapeutic drugs (doxorubicin and etoposide). Multimodal single-cell sequencing indicates T-cell receptor (TCR), NF-κB, and JAK/STAT signaling pathways (previously associated with drug resistance) as putative mediators of SE-induced drug resistance. In support, inhibition of TCR-signaling and Protein kinase C (upstream of NF-κB) counteracts SE-induced rescue from drug-induced cell death. Inversely, SE cannot rescue from cell death induced by the proteasome/NF-κB inhibitor bortezomib. Inhibition of JAK/STAT only blocks rescue in patients whose malignant T-cell survival is dependent on SE-induced cytokines, suggesting 2 distinct ways SE can induce drug resistance. In conclusion, we show that S aureus enterotoxins induce drug resistance in primary malignant T cells. These findings suggest that S aureus enterotoxins cause clinical treatment resistance in patients with SS, and antibacterial measures may improve the outcome of cancer-directed therapy in patients harboring S aureus.

The Methyltransferases METTL7A and METTL7B Confer Resistance to Thiol-Based Histone Deacetylase Inhibitors

Histone deacetylase inhibitors (HDACi) are part of a growing class of epigenetic therapies used for the treatment of cancer. Although HDACis are effective in the treatment of T-cell lymphomas, treatment of solid tumors with this class of drugs has not been successful. Overexpression of the multidrug resistance protein P-glycoprotein (P-gp), encoded by ABCB1, is known to confer resistance to the HDACi romidepsin in vitro, yet increased ABCB1 expression has not been associated with resistance in patients, suggesting that other mechanisms of resistance arise in the clinic. To identify alternative mechanisms of resistance to romidepsin, we selected MCF-7 breast cancer cells with romidepsin in the presence of the P-gp inhibitor verapamil to reduce the likelihood of P-gp-mediated resistance. The resulting cell line, MCF-7 DpVp300, does not express P-gp and was found to be selectively resistant to romidepsin but not to other HDACis such as belinostat, panobinostat, or vorinostat. RNA-sequencing analysis revealed upregulation of the mRNA coding for the putative methyltransferase, METTL7A, whose paralog, METTL7B, was previously shown to methylate thiol groups on hydrogen sulfide and captopril. As romidepsin has a thiol as the zinc-binding moiety, we hypothesized that METTL7A could inactivate romidepsin and other thiol-based HDACis via methylation of the thiol group. We demonstrate that expression of METTL7A or METTL7B confers resistance to thiol-based HDACis and that both enzymes are capable of methylating thiol-containing HDACis. We thus propose that METTL7A and METTL7B confer resistance to thiol-based HDACis by methylating and inactivating the zinc-binding thiol.

Beyond BRCA: Diagnosis and management of homologous recombination repair deficient pancreatic cancer

Approximately 4%-7% of patients diagnosed with pancreatic adenocarcinoma (PDAC) are found to harbor deleterious germline mutations in BRCA1 and/or BRCA2. Loss of function of BRCA1 and/or BRCA2 results in deficiency in homologous recombination repair (HRR), a critical DNA repair pathway, and confers sensitivity to certain DNA damaging agents, including platinum chemotherapy and PARP inhibitors. The PARP inhibitor olaparib is food and drug administration (FDA) approved for use in pancreatic cancer based on the POLO trial, which found that maintenance olaparib significantly prolonged progression free survival compared to placebo among patients with germline BRCA1 or BRCA2 mutations and metastatic PDAC that had not progressed following frontline platinum-based chemotherapy. Recently, there has been considerable interest in identifying patients without BRCA inactivation whose tumors also exhibit properties of HRR deficiency and thus may be susceptible to therapies with proven benefit in cancers harboring BRCA mutations. Here, we discuss methods for identification of HRR-deficiency and review the management of HRR-deficient cancers with a focus on HRR-deficient PDAC.

Analysis of data from the PALOMA-3 trial confirms the efficacy of palbociclib and offers alternatives for novel assessment of clinical trials

PURPOSE

There remains a need for novel therapies for patients with metastatic breast cancer (MBC). We explore the use of a novel biomarker of survival that could potentially expedite the testing of novel therapies.

METHODS

We applied a tumor regression-growth model to radiographic measurement data from 393 women with MBC enrolled in PALOMA-3 examining efficacy of palbociclib in disease that had progressed on previous endocrine therapy. 261 and 132 women were randomized to fulvestrant plus palbociclib or placebo, respectively. We estimated rates of regression (d) and growth (g) of the sensitive and resistant fractions of tumors, respectively. We compared the median g of both arms. We examined the relationship between g and progression-free and overall survival (OS).

RESULTS

As in other tumors, g is a biomarker of OS. In PALOMA-3, we found significant differences in g among patients with tumors sensitive to endocrine therapy but not amongst resistant tumors, emulating clinical trial results. Subgroup analysis found favorable g values in visceral metastases treated with palbociclib. Palbociclib efficacy demonstrated by slower g values was evident early in the trial, twelve weeks after the first 28 patients had been enrolled.

CONCLUSION

Values of g, estimated using data collected while a patient is enrolled in a clinical trial is an excellent biomarker of OS. Our results correlate with the survival outcomes of PALOMA-3 and argue strongly for using g as a clinical trial endpoint to help inform go/no-go decisions, improve trial efficiency, and deliver novel therapies to patients sooner.

Novel Therapeutic Strategies Exploiting the Unique Properties of Neuroendocrine Neoplasms

BACKGROUND

Over the last few decades of treatment, the outcomes for at least some subsets of neuroendocrine neoplasms (NENs) have improved. However, the identification of new vulnerabilities for this heterogeneous group of cancers remains a priority.

METHODS

Using two libraries of compounds selected for potential repurposing, we identified the inhibitors of nicotinamide phosphoribosyltransferase (NAMPT) and histone deacetylases (HDAC) as the agents with the highest activity. We validated the hits in an expanded set of neuroendocrine cell lines and examined the mechanisms of action.

RESULTS

In Kelly, NH-6, and NCI-H82, which are two neuroblastoma and one small cell lung cancer cell lines, respectively, metabolic studies suggested that cell death following NAMPT inhibition is the result of a reduction in basal oxidative phosphorylation and energy production. NAMPT is the rate-limiting enzyme in the production of NAD+, and in the three cell lines, NAMPT inhibition led to a marked reduction in the ATP and NAD+ levels and the catalytic activity of the citric acid cycle. Moreover, comparative analysis of the mRNA expression in drug-sensitive and -insensitive cell lines found less dependency of the latter on oxidative phosphorylation for their energy requirement. Further, the analysis of HDAC and NAMPT inhibitors administered in combination found marked activity using low sub-lethal concentrations of both agents, suggesting a synergistic effect.

CONCLUSION

These data suggest NAMPT inhibitors alone or in combination with HDAC inhibitors could be particularly effective in the treatment of neuroendocrine neoplasms.

Highlights of ASCO 2023

Considering presentations at this year’s ASCO annual meeting, this editorial highlights a number of studies of interest, from adjuvant therapy studies to tumor agnostic therapy.

A Phase I Study of a Combination of Liposomal Irinotecan and Veliparib in Solid Tumors

BACKGROUND

Multiple preclinical studies have shown cytotoxic synergy involving combinations of poly (ADP-ribose) polymerase (PARP) inhibitors and topoisomerase 1 (TOP1) inhibitors, but such combinations have proven too toxic in clinical trials. Liposomal irinotecan (nal-IRI) achieved similar intratumoral exposure with better antitumor activity than the conventional TOP1 inhibitor irinotecan in preclinical models. Tumor targeted delivery of TOP1 inhibitor using nal-IRI and an intermittent schedule of administration of PARP inhibitor may provide a tolerable combination.

METHODS

A phase I study was performed to evaluate the safety and tolerability of escalating doses of nal-IRI and the PARP inhibitor veliparib in patients with solid tumors resistant to standard treatments. Nal-IRI was administered on days 1 and 15 and veliparib on days 5-12 and 19-25 in 28-day cycles.

RESULTS

Eighteen patients were enrolled across 3 dose levels. Five patients encountered dose-limiting toxicities, including grade 3 diarrhea lasting more than 72 h in 3 patients and 1 patient each with grade 4 diarrhea and grade 3 hyponatremia. The most common grade 3 or 4 toxicities included diarrhea (50% of patients), nausea (16.6%), anorexia, and vomiting (11.1% each) (Table 1). There was no difference in frequencies of adverse events based on UGT1A1*28 status or prior opioid use (Table 1).

CONCLUSION

The clinical trial was terminated due to high frequency of unacceptable gastrointestinal toxicities, which precluded dose escalation of veliparib in combination with nal-IRI (ClinicalTrials.gov Identifier: NCT02631733).

Back to the Future, II

This editorial reflects on the vision and focus of The Oncologist, both historically and with a look toward the future.

Abstract PR020: Cholinergic modulation of T lymphocytes in pancreatic adenocarcinoma

Immunotherapy, which can produce durable responses in some cancers, has generally proven ineffective in PDAC, partially due to an immunosuppressive tumor immune microenvironment (TIME). Adjunctive therapies to sensitize PDAC to immunotherapy have the potential to greatly improve survival for patients with PDAC. We have shown that parasympathetic signaling via the vagus nerve inhibits PDAC by suppressing cancer stem cells. Cholinergic signaling through the Muscarinic Acetylcholine Receptor 1 (Chrm1) mediates this phenomenon. The effect of cholinergic signaling on the tumor immune microenvironment is unknown. Our objective is to investigate if loss of Chrm1 or cholinergic signaling impairs anti-tumor immune responses. We used two models of PDAC a) the KRasLSL G12D/+;Trp53R172H/+;Pdx1-Cre (KPC) autochthonous mouse model of PDAC crossed with Chrm1 knockout mice (KPCM) and b) orthotopic PDAC transplantation models. The composition of the TIME and tumor kinetics of these models were assessed, and the effect of genetic loss or pharmacological inhibition of CHRM1 on T lymphocytes function was examined. Inflammatory markers were analyzed in plasma samples from PDAC patients enrolled in a Phase 0/window of opportunity study of the cholinergic agonist, bethanechol, prior to surgery. Results show that loss of Chrm1 is associated with decreased T cell infiltration in the TIME of PDAC and increased tumor growth. CD8+ T cells deficient in Chrm1 demonstrate impaired proliferation, activation and suppression of TCF1, a transcription factor with well described roles in T cell development and maintenance of effector T cell function. Analysis of paired plasma samples obtained from patients treated with the cholinergic agonist, bethanechol show increased expression of CCL5, a chemokine with known roles in T cell migration in the TIME as well as suppression of a number of other inflammatory cytokines including TNF-alpha. These data suggest that cholinergic signaling via CHRM1 on T lymphocytes promotes CD8+ T cell infiltration into the TIME and maintenance of anti-tumor immune responses.

Citation Format: Ruth A. White, Quin T. Waterbury, Yosuke Ochiai, Leah B. Zamechek, Susan E. Bates, Timothy C. Wang. Cholinergic modulation of T lymphocytes in pancreatic adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr PR020.

Tumor Growth Rate Informs Treatment Efficacy in Metastatic Pancreatic Adenocarcinoma: Application of a Growth and Regression Model to Pivotal Trial and Real-World Data

BACKGROUND

Methods for screening agents earlier in development and strategies for conducting smaller randomized controlled trials (RCTs) are needed.

METHODS

We retrospectively applied a tumor growth model to estimate the rates of growth of pancreatic cancer using radiographic tumor measurements or serum CA 19-9 values from 3033 patients with stages III-IV PDAC who were enrolled in 8 clinical trials or were included in 2 large real-world data sets.

RESULTS

g correlated inversely with OS and was consistently lower in the experimental arms than in the control arms of RCTs. At the individual patient level, g was significantly faster for lesions metastatic to the liver relative to those localized to the pancreas. Regardless of regimen, g increased toward the end of therapy, often by over 3-fold.

CONCLUSIONS

Growth rates of PDAC can be determined using radiographic tumor measurement and CA 19-9 values. g is inversely associated with OS and can differentiate therapies within the same trial and across trials. g can also be used to characterize changes in the behavior of an individual's PDAC, such as differences in the growth rate of lesions based on metastatic site, and the emergence of chemoresistance. We provide examples of how g can be used to benchmark phase II and III clinical data to a virtual reference arm to inform go/no go decisions and consider novel trial designs to optimize and accelerate drug development.

Cost-effectiveness of neoadjuvant FOLFIRINOX versus gemcitabine plus nab-paclitaxel in borderline resectable/locally advanced pancreatic cancer patients

BACKGROUND

The 2020 National Comprehensive Cancer Network guidelines recommend neoadjuvant FOLFIRINOX or neoadjuvant gemcitabine plus nab-paclitaxel (G-nP) for borderline resectable/locally advanced pancreatic ductal adenocarcinoma (BR/LA PDAC).

AIM

The purpose of our study was to compare treatment outcomes, toxicity profiles, costs, and quality-of-life measures between these two treatments to further inform clinical decision-making.

METHODS AND RESULTS

We developed a decision-analytic mathematical model to compare the total cost and health outcomes of neoadjuvant FOLFIRINOX against G-nP over 12 years. The model inputs were estimated using clinical trial data and published literature. The primary endpoint was incremental cost-effectiveness ratios (ICERs) with a willingness-to-pay threshold of $100 000 per quality-adjusted-life-year (QALY). Secondary endpoints included overall (OS) and progression-free survival (PFS), total cost of care, QALYs, PDAC resection rate, and monthly treatment-related adverse events (TRAE) costs (USD). FOLFIRINOX was the cost-effective strategy, with an ICER of $60856.47 per QALY when compared to G-nP. G-nP had an ICER of $44639.71 per QALY when compared to natural history. For clinical outcomes, more patients underwent an "R0" resection with FOLFIRINOX compared to G-nP (84.9 vs. 81.0%), but FOLFIRINOX had higher TRAE costs than G-nP ($10905.19 vs. $4894.11). A one-way sensitivity analysis found that the ICER of FOLFIRINOX exceeded the threshold when TRAE costs were higher or PDAC recurrence rates were lower.

CONCLUSION

Our modeling analysis suggests that FOLFIRNOX is the cost-effective treatment compared to G-nP for BR/LA PDAC despite having a higher cost of total care due to TRAE costs. Trial data with sufficient follow-up are needed to confirm our findings.

Long-term follow-up experience with adjuvant therapy after irreversible electroporation of locally advanced pancreatic cancer

BACKGROUND

Irreversible electroporation (IRE) expands the surgical options for patients with unresectable pancreatic cancer. This study evaluated for differences in survival stratified by type of IRE and receipt of adjuvant chemotherapy.

METHODS

Patients with locally advanced pancreatic cancer treated by IRE (2012-2020) were retrospectively included. Overall survival (OS) and recurrence-free survival (RFS) were compared by type of IRE (in situ for local tumor control or IRE of potentially positive margins with resection) and by receipt of adjuvant chemotherapy.

RESULTS

Thirty-nine patients had IRE in situ, 61 had IRE for margin extension, and 19 received adjuvant chemotherapy. Most (97.00%) underwent induction chemotherapy. OS was 28.71 months (interquartile range [IQR] 19.17, 51.19) from diagnosis, with no difference by IRE type (hazard ratio [HR] 1.05 for margin extension [p = 0.85]) or adjuvant chemotherapy (HR 1.14 [p = 0.639]). RFS was 8.51 months (IQR 4.95, 20.17) with no difference by IRE type (HR 0.90 for margin extension [p = 0.694]) or adjuvant chemotherapy (HR 0.90 [p = 0.711]).

CONCLUSION

These findings suggest that adjuvant therapy may have limited benefit for patients treated with induction chemotherapy followed by local control with IRE for unresectable pancreatic cancer. Further study of the duration and timing of systemic therapy is warranted to maximize benefit and limit toxicity.

Supporting Patients with Cancer after Dobbs v. Jackson Women's Health Organization

In the context of cancer, whether or not to choose pregnancy termination represents a difficult and multifaceted decision. In this editorial, members of The Oncologist editorial team attempt to contextualize the potential implications of the recent Supreme Court decision in Dobbs v. Jackson Women’s Health Organizationfor patients with cancer.

Influence of cancer on COVID-19 incidence, outcomes, and vaccine effectiveness: A Prospective Cohort Study of U.S. Veterans

Purpose

Coronavirus disease 2019 (COVID-19) has been a constant health threat since its emergence. Amongst risk factors proposed, a diagnosis of cancer has been worrisome. We report the impact of cancer and other risk factors in US Veterans receiving care at Veterans Administration (VA) Hospitals, their adjusted odds ratio (aOR) for infection and death, and report on the impact of vaccines on the incidence and severity of COVID-19 infections in Veterans without/with cancer.

Methods

We conducted a cohort study of US Veterans without/with cancer by mining VA COVID-19 Shared Data Resource (CSDR) data using the VA Informatics and Computing Infrastructure (VINCI). Our observation period includes index dates from 14DEC2020 to 25JAN2022, encompassing both the delta and omicron waves in the US.

Results

We identified 915,928 Veterans, 24% of whom were African Americans who had undergone COVID testing–688,541 were and 227,387 were not vaccinated. 157,072 had a cancer diagnosis in the preceding two years. Age emerged as the major risk factor, with gender, BMI, and (Elixhauser) comorbidity contributing less. Among veterans with solid tumors other than lung cancer, risks of infection and death within 60 days were comparable to Veterans without cancer. However, those with hematologic malignancies fared worse. Vaccination was highly effective across all cancer cohorts; the respective rates of infection and death after infection were 8% and 5% among the vaccinated compared to 47% and 10% in the unvaccinated. Amongst vaccinated, increased risk of infection was noted in both, Veterans with hematologic malignancy treated with chemotherapy (HR, 2.993, P < 0.0001) or targeted therapies (HR, 1.781, P < 0.0001), and in solid tumors treated with either chemotherapy (HR 2.328, 95%CI 2.075–2.611, P < 0.0001) or targeted therapies (HR 1.328, P < 0.0001) when compared to those not on treatment.

Conclusions

Risk for COVID-19 infection and death from infection vary based on cancer type and therapies administered. Importantly and encouragingly, the duration of protection from infection following vaccination in Veterans with a diagnosis of cancer was remarkably like those without a cancer diagnosis. Veterans with hematologic malignancies are especially vulnerable, with lower vaccine effectiveness (VE).

Novel biomarkers in NSCLC: Radiomic analysis, kinetic analysis, and circulating tumor DNA

Current radiographic methods of measuring treatment response for patients with nonsmall cell lung cancer have significant limitations. Recently, new modalities using standard of care images or minimally invasive blood-based DNA tests have gained interest as methods of evaluating treatment response. This article highlights three emerging modalities: radiomic analysis, kinetic analysis and serum-based measurement of circulating tumor DNA, with a focus on the clinical evidence supporting these methods. Additionally, we discuss the possibility of combining these modalities to develop a robust biomarker with strong correlation to clinically meaningful outcomes that could impact clinical trial design and patient care. At Last, we focus on how these methods specifically apply to a Veteran population.

Abstract 4083: Case study of single-cell protein activity-based drug prediction and validation for precision treatment of cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive biliary adenocarcinoma, with a median survival ranging from 12 to 37 months and no effective treatment options [Dhanasekaran et al. 2013]. Studies of the CCA tumor micro-environment (TME) and intratumoral heterogeneity have been limited, despite clinically significant interaction between tumor and stromal or immune components across other tumor types. Single-cell RNA Sequencing (scRNASeq) has emerged as a valuable technique to characterize the TME. Here we present a case study profiling CCA TME at the resolution of scRNASeq, and the first application of a unique OncoTarget (OTar) and OncoTreat (OTr) approach [Alvarez et al. 2018, Zeleke et al. 2020, Mundi et al. 2021] to predict and identify actionable drug targets at the single-cell level. These are both CLIA-certified algorithms for personalized drug prediction, now adapted for the first time to drug sensitivity prediction at the level of individual tumor cells. scRNASeq from a human CCA sample revealed significant tumor immune infiltration, with T-cells comprising the largest population, and fewer than 10% of cells identified as tumor cells, such that transcriptional profiles from RNA-Seq derived from whole tumor samples would be dominated by non-tumor cells. VIPER-based protein activity inference of tumor cells identified three sub-populations, not distinguished by gene expression alone [Alvarez et al. 2016]. These were characterized by upregulation of KRAS pathway, TNFa signaling with epithelial-mesenchymal transition, and upregulation of MYC targets, respectively. Consensus OTar/OTr drug prediction analysis on both scRNASeq tumor cells and bulk RNA-Seq of an engrafted PDX model from resected tumor at the time of biopsy ranked Glasdegib, Plicamycin, Flavopiridol, AT9283, and Dacinostat as the top 5 drugs with best overall tumor cell coverage. Therefore, we administered these drugs to a cohort of 8 PDX-bearing mice per treatment arm. Dacinostat and Plicamycin significantly reduced tumor growth rate (p=0.007 and p=0.03, respectively), with Dacinostat stabilizing tumor size over 28 days of treatment. Both of these drugs significantly extended survival time by Kaplan-Meier regression (p=0.001 and p=0.03, respectively). Furthermore, scRNASeq data of drug-treated PDXs showed that Dacinostat uniformly depleted all three tumor sub-populations compared to Vehicle control, whereas one of the tumor sub-clusters was resistant to Plicamycin, consistent with single-cell drug sensitivity predicted by OTr.

Given the in vivo activity of these two drugs in inhibiting tumor growth, and the effectiveness of Dacinostat across observed tumor cell phenotypes, as well as the high immune infiltration of this CCA sample, these drugs may be translated into pre-clinical and clinical trials alone and in combination with checkpoint immunotherapy.

Citation Format: Lorenzo Tomassoni, Aleksandar Obradovic, Filemon Dela Cruz, Daoqi Yu, Elise Fraser, Susan E. Bates, Yvonne Saenger, Andrea Califano. Case study of single-cell protein activity-based drug prediction and validation for precision treatment of cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4083.

A Histone Deacetylase Inhibitor Induces Acetyl-CoA Depletion Leading to Lethal Metabolic Stress in RAS-Pathway Activated Cells

Simple Summary

Epigenetic therapies have been difficult to translate to solid tumors, in part because a lack of a full mechanistic understanding has not allowed the selection of tumors most likely to benefit from the therapies. Here we identified a RAS-phenotype that can be targeted by the histone deacetylase inhibitor (HDACi) romidepsin. We showed that the hyperacetylation induced by romidepsin depletes acetyl-CoA, the cell donor substrate for acetylation, and it leads to metabolic stress and death in KRAS-activated cells. Transcriptomic analysis confirmed that perturbation of two acetyl-CoA generation pathways (fatty acid metabolism and branched-chain amino acid (BCAA) metabolism) were correlated with HDACi sensitivity in a 608-cell line panel and in patients treated with belinostat. Our analysis highlights the potential utility of an acetyl-CoA phenotype to sharpen treatment choices for RAS-activated tumors, and it suggests that acetyl-CoA depletion could be a key effect underlying the myriad cellular responses that follow HDAC inhibition.

Abstract

Background: The mechanism of action of romidepsin and other histone deacetylase inhibitors is still not fully explained. Our goal was to gain a mechanistic understanding of the RAS-linked phenotype associated with romidepsin sensitivity. Methods: The NCI60 dataset was screened for molecular clues to romidepsin sensitivity. Histone acetylation, DNA damage, ROS production, metabolic state (real-time measurement and metabolomics), and gene expression alterations (transcriptomics) were determined in KRAS-WT versus KRAS-mutant cell groups. The search for biomarkers in response to HDACi was implemented by supervised machine learning analysis on a 608-cell transcriptomic dataset and validated in a clinical dataset. Results: Romidepsin treatment induced depletion in acetyl-CoA in all tested cell lines, which led to oxidative stress, metabolic stress, and increased death—particularly in KRAS-mutant cell lines. Romidepsin-induced stresses and death were rescued by acetyl-CoA replenishment. Two acetyl-CoA gene expression signatures associated with HDACi sensitivity were derived from machine learning analysis in the CCLE (Cancer Cell Line Encyclopedia) cell panel. Signatures were then validated in the training cohort for seven HDACi, and in an independent 13-patient cohort treated with belinostat. Conclusions: Our study reveals the importance of acetyl-CoA metabolism in HDAC sensitivity, and it highlights acetyl-CoA generation pathways as potential targets to combine with HDACi.

Neoadjuvant chemoradiation alters the immune microenvironment in pancreatic ductal adenocarcinoma

Patients with pancreatic ductal adenocarcinoma (PDAC) have a grim prognosis despite complete surgical resection and intense systemic therapies. While immunotherapies have been beneficial with many different types of solid tumors, they have almost uniformly failed in the treatment of PDAC. Understanding how therapies affect the tumor immune microenvironment (TIME) can provide insights for the development of strategies to treat PDAC. We used quantitative multiplexed immunofluorescence (qmIF) quantitative spatial analysis (qSA), and immunogenomic (IG) analysis to analyze formalin-fixed paraffin embedded (FFPE) primary tumor specimens from 44 patients with PDAC including 18 treated with neoadjuvant chemoradiation (CRT) and 26 patients receiving no treatment (NT) and compared them with tissues from 40 treatment-naïve melanoma patients. We find that relative to NT tumors, CD3+ T cell infiltration was increased in CRT treated tumors (p = .0006), including increases in CD3+CD8+ cytotoxic T cells (CTLs, p = .0079), CD3+CD4+FOXP3- T helper cells (Th, p = .0010), and CD3+CD4+FOXP3+ regulatory T cells (Tregs, p = .0089) with no difference in CD68+ macrophages. IG analysis from micro-dissected tissues indicated overexpression of genes involved in antigen presentation, T cell activation, and inflammation in CRT treated tumors. Among treated patients, a higher ratio of Tregs to total T cells was associated with shorter survival time (p = .0121). Despite comparable levels of infiltrating T cells in CRT PDACs to melanoma, PDACs displayed distinct spatial profiles with less T cell clustering as defined by nearest neighbor analysis (p < .001). These findings demonstrate that, while CRT can achieve high T cell densities in PDAC compared to melanoma, phenotype and spatial organization of T cells may limit benefit of T cell infiltration in this immunotherapy-resistant tumor.

Dual Inhibition of Histone Deacetylases and the Mechanistic Target of Rapamycin Promotes Apoptosis in Cell Line Models of Uveal Melanoma

Purpose

Over 90% of uveal melanomas harbor pathogenic variants of the GNAQ or GNA11 genes that activate survival pathways. As previous studies found that Ras-mutated cell lines were vulnerable to a combination of survival pathway inhibitors and the histone-deacetylase inhibitor romidepsin, we investigated whether this combination would be effective in models of uveal melanoma.

Methods

A small-scale screen of inhibitors of bromodomain-containing protein 4 (BRD4; OTX-015), extracellular signal-related kinase (ERK; ulixertinib), mechanistic target of rapamycin (mTOR; AZD-8055), or phosphoinositide 3-kinase (PI3K; GDC-0941) combined with a clinically relevant administration of romidepsin was performed on a panel of uveal melanoma cell lines (92.1, Mel202, MP38, and MP41) and apoptosis was quantified by flow cytometry after 48 hours. RNA sequencing analysis was performed on Mel202 cells treated with romidepsin alone, AZD-8055 alone, or the combination, and protein changes were validated by immunoblot.

Results

AZD-8055 with romidepsin was the most effective combination in inducing apoptosis in the cell lines. Increased caspase-3 and PARP cleavage were noted in the cell lines when they were treated with romidepsin and mTOR inhibitors. RNA sequencing analysis of Mel202 cells revealed that apoptosis was the most affected pathway in the romidepsin/AZD-8055-treated cells. Increases in pro-apoptotic BCL2L11 and decreases in anti-apoptotic BIRC5 and BCL2L1 transcripts noted in the sequencing analysis were confirmed at the protein level in Mel202 cells.

Conclusions

Our data suggest that romidepsin in combination with mTOR inhibition could be an effective treatment strategy against uveal melanoma due in part to changes in apoptotic proteins.

Targeting the T-Cell Lymphoma Epigenome Induces Cell Death, Cancer Testes Antigens, Immune-Modulatory Signaling Pathways

The peripheral T-cell lymphomas (PTCL) could be considered the prototypical epigenetic disease. As a disease, they are uniquely sensitive to histone deacetylase (HDAC) and DNA methyltransferase (DNMT) inhibitors, both alone and in combination, are characterized by a host of mutations in epigenetic genes, and can develop spontaneously in genetically engineered murine models predicated on established recurring mutations in (RHOAG17V) and TET2, an epigenetic gene governing DNA methylation. Given the clinical benefit of HDAC inhibitors (HDACi) and hypomethlyation agents alone and in combination in PTCL, we sought to explore a mechanistic basis for these agents in PTCL. Herein, we reveal profound class synergy between HDAC and DNMT inhibitors in PTCL, and that the combination induces degrees of gene expression that are substantially different and more extensive than that observed for the single agents. A prominent signature of the combination relates to the transcriptional induction of cancer testis antigens and genes involved in the immune response. Interestingly, TBX21 and STAT4, master regulators of TH1 differentiation, were among the genes upregulated by the combination, suggesting the induction of a TH1-like phenotype. Moreover, suppression of genes involved in cholesterol metabolism and the matrisome were also identified. We believe that these data provide a strong rationale for clinical studies, and future combinations leveraging an immunoepigenetic platform.

R-Loop-Mediated ssDNA Breaks Accumulate Following Short-Term Exposure to the HDAC Inhibitor Romidepsin

Histone deacetylase inhibitors (HDACi) induce hyperacetylation of histones by blocking HDAC catalytic sites. Despite regulatory approvals in hematological malignancies, limited solid tumor clinical activity has constrained their potential, arguing for better understanding of mechanisms of action (MOA). Multiple activities of HDACis have been demonstrated, dependent on cell context, beyond the canonical induction of gene expression. Here, using a clinically relevant exposure duration, we established DNA damage as the dominant signature using the NCI-60 cell line database and then focused on the mechanism by which hyperacetylation induces DNA damage. We identified accumulation of DNA-RNA hybrids (R-loops) following romidepsin-induced histone hyperacetylation, with single-stranded DNA (ssDNA) breaks detected by single-cell electrophoresis. Our data suggest that transcription-coupled base excision repair (BER) is involved in resolving ssDNA breaks that, when overwhelmed, evolve to lethal dsDNA breaks. We show that inhibition of BER proteins such as PARP will increase dsDNA breaks in this context. These studies establish accumulation of R-loops as a consequence of romidepsin-mediated histone hyperacetylation. We believe that the insights provided will inform design of more effective combination therapy with HDACis for treatment of solid tumors. IMPLICATIONS: Key HDAC inhibitor mechanisms of action remain unknown; we identify accumulation of DNA-RNA hybrids (R-loops) due to chromatin hyperacetylation that provokes single-stranded DNA damage as a first step toward cell death.

Antibiotics and Imiquimod for Cutaneous T-Cell Lymphoma in Veterans: A Patient Population with Agent Orange Exposure

LESSONS LEARNED

Staphylococcus aureus infection in cutaneous T-cell lymphoma (CTCL) is thought to contribute to disease progression; thus, adjunctive treatment with antibiotics warrants further investigation. This trial of antibiotic therapy followed by imiquimod in early stage CTCL was not completed because of difficulties with patient accrual.

BACKGROUND

Cutaneous T-cell lymphoma (CTCL), a form of non-Hodgkin lymphoma, is a heterogeneous group of malignancies of mature memory T lymphocytes. It has an annual age-adjusted incidence of 7.5 per million persons in the U.S. population [1]. The etiology of CTCL is unknown, but epidemiological studies have reported potential associations with environmental and occupational factors, including Agent Orange exposure in Vietnam Veterans [2]. Both topical and systemic therapies have been identified as effective in CTCL; the choice of treatment is dependent on disease stage, with the overall goal of improving symptoms given the chronic and recurrent nature of the disease. Several studies have suggested that CTCL is exacerbated by the presence of Staphylococcus aureus in the skin and can be ameliorated by treatment with antibiotics [3].

METHODS

Our study was designed to assess the effects of antibiotics and imiquimod on early stage CTCL. Patients between the ages of 30-89 years with stage I and II CTCL were eligible for enrollment. They could not be receiving concurrent therapy, and the study design included a 14-day washout period after discontinuation of CTCL therapy. The washout period was followed by doxycycline 100 mg p.o. b.i.d. for 14 days and then two packets (250 mg per packet) of imiquimod 5% cream topically to the most clinically active lesions 3 days a week (Monday, Wednesday, and Friday) for 28 days. Skin lesions were measured using the modified Severity Weighted Assessment Tool (mSWAT).

RESULTS

Our study enrolled only two patients with early stage CTCL because of difficulty locating patients with active CTCL able to discontinue all therapy. The two enrolled patients completed all therapy. One patient had a complete response after imiquimod, whereas the other patient had stable disease.

CONCLUSION

Antibiotics and imiquimod have reported activity as single agents in CTCL; we did not enroll enough patients to assess value in the sequence of antibiotic therapy followed by imiquimod.

Mitochondrial ATP fuels ABC transporter-mediated drug efflux in cancer chemoresistance

Chemotherapy remains the standard of care for most cancers worldwide, however development of chemoresistance due to the presence of the drug-effluxing ATP binding cassette (ABC) transporters remains a significant problem. The development of safe and effective means to overcome chemoresistance is critical for achieving durable remissions in many cancer patients. We have investigated the energetic demands of ABC transporters in the context of the metabolic adaptations of chemoresistant cancer cells. Here we show that ABC transporters use mitochondrial-derived ATP as a source of energy to efflux drugs out of cancer cells. We further demonstrate that the loss of methylation-controlled J protein (MCJ) (also named DnaJC15), an endogenous negative regulator of mitochondrial respiration, in chemoresistant cancer cells boosts their ability to produce ATP from mitochondria and fuel ABC transporters. We have developed MCJ mimetics that can attenuate mitochondrial respiration and safely overcome chemoresistance in vitro and in vivo. Administration of MCJ mimetics in combination with standard chemotherapeutic drugs could therefore become an alternative strategy for treatment of multiple cancers.

Positive attitudes toward clinical trials among military veterans leaves unanswered questions about poor trial accrual

Participation in clinical trials is essential to bringing novel and innovative cancer treatments to the bedside but trials that specifically enroll Veterans are relatively few. Given the inherent differences between Veterans and the general United States population, we sought to investigate awareness of and attitudes toward clinical trials among Veterans diagnosed with cancer at a large, urban Veterans Administration Medical Center in Bronx, New York. The survey was administered in 2018-2019. Questions assessed sociodemographic characteristics, health literacy, and general attitudes about clinical trials. Based on key informant interviews, we also inquired about military-specific attitudes. Univariable analyses were conducted to evaluate differences in attitudes by age (<65 v ≥65 years) and race/ethnicity (non-Hispanic black v other). Of 115 Veterans approached, 67 (58.3%) completed the survey. Approximately 95% of participants were male, 59.7% were ≥65 years old, and 41.8% were non-Hispanic black. Only 58.2% reported knowing what a clinical trial is but 78.5% of Veterans stated that they trust doctors who do medical research and 87.5% reported they would strongly consider joining a trial if their VA primary care physician recommended it. Many stated that they would be part of a clinical trial if it would help fellow Veterans in the future (93.8%) and would help scientists learn how to treat other Veterans with the same disease (93.8%). Among non-Hispanic black participants, 62.5% agreed that the government has a history of using Veterans in experiments without their knowledge compared to 34.2% of Veterans of other race/ethnicity (P = 0.03). Clearly Veterans in our study were amenable to joining clinical trials. While many are aware of past misconduct in the treatment of military personnel in research, overall attitudes toward clinical trials were favorable and were especially positive when the possibility of improving cancer care for fellow Veterans was considered. In approaching Veterans regarding participation in a clinical trial we recommend education aligned with the literacy level of the Veteran, involvement of the VA primary care provider in clinical trial decisions, and awareness of a Veteran's altruism to help others.

Gemcitabine plus nab-paclitaxel versus FOLFIRINOX for unresected pancreatic cancer: Comparative effectiveness and evaluation of tumor growth in Veterans

PURPOSE

Advanced, unresectable pancreatic cancer is often treated with either gemcitabine plus nab-paclitaxel (Gem/NabP) or FOLFIRINOX, although these regimens have never been compared in a head-to-head trial. In this study, we compared these two regimens using Veterans Administration (VA) data and evaluated the use of a novel tumor growth formula to predict outcomes.

METHODS

We identified 670 Veterans from national VA data with unresected stage II-IV pancreatic adenocarcinoma diagnosed between 2003 and 2016 who were treated with either first-line Gem/NabP or FOLFIRINOX. We compared overall survival (OS) and adverse events by treatment using propensity scores (PS) to account for allocation bias. Using longitudinal CA19-9 biomarker information we then fit the data to a novel tumor growth equation, comparing growth with OS.

RESULTS

We found no difference in PS-adjusted (hazard ratio [HR] 1.00; 95% confidence interval [95% CI] 0.84-1.20) or PS-matched (HR: 0.93; 95% CI: 0.76-1.13) OS between the two treatment groups. Tumor growth analysis revealed similar growth parameter values for Gem/NabP and FOLFIRINOX (P = .074 for difference).

CONCLUSIONS

Gem/NabP appeared noninferior to FOLFIRINOX for survival outcomes for advanced pancreatic adenocarcinoma based on national VA data. Biomarker-based growth equations may be useful for monitoring treatment response and predicting prognosis for pancreatic cancer.

Two decades of research toward the treatment of locally advanced and metastatic pancreatic cancer: Remarkable effort and limited gain

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy that is diagnosed at the locally advanced or metastatic stage in approximately 80% of cases. Relative to other tumor types, progress in the treatment of this disease has been painfully slow. While agents targeting DNA repair have proven successful in a subset of patients, the majority of PDACs do not exhibit validated molecular targets. Hence, conventional chemotherapy remains at the forefront of therapy for this disease. In this review, we study two decades of efforts to improve upon the gemcitabine backbone - 67 phase II and III trials enrolling 16,446 patients - that culminated in the approvals of gemcitabine/nab-paclitaxel (Gem/NabP) and FOLFIRINOX. Today, these remain gold standards for the first-line treatment of locally advanced unresectable and metastatic PDAC, while ongoing efforts focus on improving upon the Gem/NabP backbone. Because real world data often do not reflect the data of randomized controlled trials (RCTs), we also summarize the retrospective evidence comparing the efficacy of Gem/NabP and FOLFIRINOX in the first-line setting - 29 studies reporting a median overall survival of 10.7 and 9.1 months for FOLFIRINOX and Gem/NabP, respectively. These values are surprisingly comparable to those reported by the pivotal RCTs at 11.1 and 8.5 months. Finally, there is a paucity of RCT data regarding the efficacy of second-line therapy. Hence, we conclude this review by summarizing the data that ultimately demonstrate a small but significant survival benefit of second-line therapy with Gem/NabP or FOLFIRINOX. Collectively, these studies describe the long journey, the steady effort, and the myriad lessons to be learned from 20 years of PDAC trials to inform strategies for success in clinical trials moving forward.

A Medical Pearl Harbor: Pandemic Uncovers Societal Fissures and Leadership Breaches

The Editors of The Oncologist remark on recent national events and call for new strategies for the New Year.

Drug resistant cells with very large proliferative potential grow exponentially in metastatic prostate cancer

Most metastatic cancers develop drug resistance during treatment and continue to grow, driven by a subpopulation of cancer cells unresponsive to the therapy being administered. There is evidence that metastases are formed by phenotypically plastic cancer cells with stem-cell like properties. Currently the population structure and growth dynamics of the resulting metastatic tumors is unknown. Here, using scaling analysis of clinical data of tumor burden in patients with metastatic prostate cancer, we show that the drug resistant, metastasis-causing cells (MCC) are capable of producing drug resistant, exponentially growing tumors, responsible for tumor growth as a patient receives different treatments.

Metastatic and recurrent adrenocortical cancer is not defined by its genomic landscape

Background

Adrenocortical carcinoma (ACC) is a rare, often-aggressive neoplasm of the adrenal cortex, with a 14–17 month median overall survival. We asked whether tumors from patients with advanced or metastatic ACC would offer clues as to putative genes that might have critical roles in disease progression or in more aggressive disease biology.

Methods

We conducted comprehensive genomic and expression analyses of ACCs from 43 patients, 30 female, and 42 from metastatic sites, including deep sequencing, copy number analysis, mRNA expression and microRNA arrays.

Results

Copy number gains and losses were similar to that previously reported for ACC. We identified a median mutation rate of 3.38 per megabase (Mb). The mutational signature was characterized by a predominance of C > T, C > A and T > C transitions. Only cancer genes TP53 (26%) and beta-catenin (CTNNB1, 14%) were mutated in more than 10% of samples. The TCGA-identified putative cancer genes MEN1 and PRKAR1A were found in low frequency—4.7 and 2.3%, respectively. The majority of the mutations were in genes not implicated in the etiology or maintenance of cancer. Specifically, amongst the 38 genes that were mutated in more than 9% of samples, only four were represented in Tier 1 of the 576 COSMIC Cancer Gene Census (CCGC). Thus, 82% of genes found to have mutations likely have no role in the etiology or biology of ACC; while the role of the other 18%, if any, remains to be proven. Finally, the transcript length for the 38 most frequently mutated genes in ACC is statistically longer than the average of all coding genes, raising the question of whether transcript length in part determined mutation probability.

Conclusions

We conclude that the mutational and expression profiles of advanced and metastatic tumors are very similar to those from newly diagnosed patients—with very little in the way of genomic aberration to explain differences in biology. With relatively low mutation rates, few major oncogenic drivers, and loss of function mutations in several epigenetic regulators, an epigenetic basis for ACC may be postulated and serve as the basis for future studies.

Randomized Phase III Trial of Pegvorhyaluronidase Alfa With Nab-Paclitaxel Plus Gemcitabine for Patients With Hyaluronan-High Metastatic Pancreatic Adenocarcinoma

PURPOSE

To evaluate the efficacy and safety of pegvorhyaluronidase alfa (PEGPH20) plus nab-paclitaxel/gemcitabine (AG) in patients with hyaluronan-high metastatic pancreatic ductal adenocarcinoma (PDA).

PATIENTS AND METHODS

HALO 109-301 was a phase III, randomized, double-blind, placebo-controlled study. Patients ≥ 18 years of age with untreated, metastatic, hyaluronan-high PDA were randomly assigned 2:1 to PEGPH20 plus AG or placebo plus AG. Treatment was administered intravenously in 4-week cycles (3 weeks on, 1 week off) until progression or intolerable adverse events: PEGPH20 3.0 µg/kg twice per week for cycle 1 and once per week thereafter; nab-paclitaxel 125 mg/m² once per week; and gemcitabine 1,000 mg/m² once per week. The primary end point was overall survival (OS); secondary end points included progression-free survival (PFS), objective response rate (ORR), and safety. Response was independently assessed per RECIST v1.1.

RESULTS

At data cutoff, 494 patients were randomly assigned, with 492 (327 for PEGPH20 and 165 for placebo) included in intention-to-treat analyses. Baseline characteristics were balanced for PEGPH20 plus AG versus placebo plus AG. There were 330 deaths, with a median OS of 11.2 months for PEGPH20 plus AG versus 11.5 months for placebo plus AG (hazard ratio [HR], 1.00; 95% CI, 0.80 to 1.27; P = .97); median PFS was 7.1 months versus 7.1 months (HR, 0.97 [95% CI, 0.75 to 1.26]); ORR was 47% versus 36% (ORR ratio, 1.29 [95% CI, 1.03 to 1.63]). Grade ≥ 3 adverse events with a ≥ 2% higher rate with PEGPH20 plus AG than with placebo plus AG included fatigue (16.0% v 9.6%), muscle spasms (6.5% v 0.6%), and hyponatremia (8.0% v 3.8%).

CONCLUSION

The addition of PEGPH20 to AG increased the ORR but did not improve OS or PFS. The safety profile of PEGPH20 plus AG was consistent with that found in previous studies. These results do not support additional development of PEGPH20 in metastatic PDA.

Neutrophil-to-lymphocyte ratio as a prognostic indicator for overall and cancer-specific survival in squamous cell carcinoma of the head and neck

BACKGROUND

Neutrophil-to-lymphocyte ratio (NLR) is a biomarker that is correlated with systemic inflammation and poor prognosis in solid tumors. We investigated the value of NLR in predicting survival in a large population of head and neck cancer patients in the United States.

METHODS

We performed a retrospective cohort study of Veterans Affairs patients with head and neck squamous cell carcinoma (HNSCC) diagnosed between January 2000 and December 2017. We compared 5-year overall survival and cancer-specific survival for different NLR tertiles using cox proportional hazards modeling with adjustment for covariates.

RESULTS

The primary cohort consisted of 14 644 subjects of which 99% were male. Relative to patients with NLRs in the lower tertile, patients with NLRs in the top tertile had an 71% increased hazard of all-cause mortality (P < .001) and 44% increased hazard of cancer-specific mortality (P < .001) at 5 years.

CONCLUSIONS

Elevated NLR in HNSCC confers a poor prognosis.

Emerging Therapeutic Implications of STK11 Mutation: Case Series

STK11 was first recognized as a tumor suppressor gene in the late 1990s based on linkage analysis of patients with Peutz-Jeghers syndrome. STK11 encodes LKB1, an intracellular serine-threonine kinase involved in cellular metabolism, cell polarization, regulation of apoptosis, and DNA damage response. Recurrent somatic loss-of-function mutations occur in multiple cancer types, most notably in 13% of lung adenocarcinomas. Recent reports indicate that KRAS-mutant non-small cell lung cancers harboring co-mutations in STK11 do not respond to PD-1 axis inhibitors. We present three patients with STK11-mutated tumors and discuss the proposed mechanisms by which germline and somatic alterations in STK11 promote carcinogenesis, potential approaches for therapeutic targeting, and the new data on resistance to immune checkpoint inhibitors. KEY POINTS: STK11 is a tumor suppressor gene, and loss-of-function mutations are oncogenic, due at least in part to loss of AMPK regulation of mTOR and HIF-1-α. Clinical trials are under way, offering hope to patients whose STK11-mutated tumors are refractory and/or have progressed on chemotherapeutic regimens. Whether gastrointestinal cancers with STK11 loss of function will show the same outcome and potential refractoriness to immune therapy that were reported for lung cancer is unknown. However, physicians managing such patients should consider the experience in lung cancer, particularly outside the context of a clinical trial. In the CheckMate-057 trial lung tumors harboring co-mutations in KRAS and STK11 had an inferior response to PD-1 axis inhibitors. Coupled with the observation that STK11-mutated tumors were found to have a cold immune microenvironment regardless of KRAS status, the conclusion could extend to KRAS wild-type tumors with STK11 mutation. Current data suggest that the use of PD-1 axis inhibitors may be ill advised in the presence of STK11 mutation.

PD-1 Pandemonium at the American Association for Cancer Research Annual Meeting

This editorial describes the results of discussions between the U.S. FDA Oncology Center of Excellence and members of six pharmaceutical companies—a forum aptly named PD‐1 Pandemonium—regarding development and regulatory approvals of immune checkpoint inhibitors.

Accrual, Publication Bias, and the Coronavirus in 2020

The era of COVID19 reflects the importance, perhaps now more than ever, of transparency in the outcomes of trials small and large. The Oncologist Clinical Trial Results (CTR) section has endeavored to provide a remedy for the persistent problem of underreporting in clinical trials in oncology and the subsequent publication bias that this practice necessarily creates. As The Oncologist celebrates its 25th Anniversary, we focus not only on the ethical and moral imperatives behind CTR, but also on the practical goal of informing the practice of treating physicians.

BRCA Mutations in Pancreas Cancer: Spectrum, Current Management, Challenges and Future Prospects

Pancreatic ductal adenocarcinoma (PDAC) remains a challenging disease to treat. Despite advances in surgical techniques, radiation, and medical therapies, the 5-year survival rate remains below 9%. Over the past decade, the genomic landscape of PDAC has been well studied and BRCA mutations have emerged as a target for the development of more effective therapies. Alterations in germline BRCA and PALB2 are detected in approximately 5-9% of patients with PDAC and can lead to homologous repair deficiency (HRD). PDAC with HRD is more susceptible to cytotoxic agents, such as platinum salts and topoisomerase inhibitors, that cause DNA damage. Furthermore, PARP inhibitors have emerged as an effective non-cytotoxic approach to treating HRD-PDAC. In addition to BRCA and PALB2, germline mutations in other genes involved in the homologous DNA repair pathway - such as ATM and RAD51 - are potential targets, as are patients with the "BRCAness" phenotype and somatic mutations in the DNA repair pathway. Given the clinical implications of germline mutation related HRD in PDAC, universal germline testing is now recommended. In this review, we will discuss current and emerging biomarkers for HRD in PDAC, treatments, and the challenges associated with them.

Prevention of Venous Thromboembolism in Pancreatic Cancer: Breaking Down a Complex Clinical Dilemma

Venous thromboembolism (VTE) frequently occurs in patients with cancer, and particularly those with pancreatic ductal adenocarcinoma (PDAC). Therapeutic anticoagulation with either low-molecular-weight heparin or a direct oral anticoagulant is clearly beneficial in patients who develop a VTE. However, whether thromboprophylaxis improves patient outcomes remains unclear. Studies assessing this risk show a 10%-25% risk of VTE, with reduction to 5%-10% with thromboprophylaxis but no impact on survival. To aid in the risk stratification of patients, several tools have been developed to identify those at highest risk for a VTE event. However, the clinical application of these risk stratification models has been limited, and most patients, even those at the highest risk, will never have a VTE event. New oral anticoagulants have greatly improved the feasibility of prophylaxis but do show increased risk of bleeding in patients with the underlying gastrointestinal dysfunction frequently found in patients with pancreatic cancer. Recently, several completed clinical trials shed new light on this complicated risk versus benefit decision. Here, we present this recent evidence and discuss important considerations for the clinician in determining whether to initiate thromboprophylaxis in patients with PDAC. IMPLICATIONS FOR PRACTICE: Given the high risk of venous thromboembolism in patients with pancreatic adenocarcinoma (PDAC), whether to initiate prophylactic anticoagulation is a complex clinical decision. This review discusses recent evidence regarding the risk stratification and treatment options for thromboprophylaxis in patients with PDAC, with the goal of providing practicing clinicians with updates on recent developments in the field. This article also highlights important considerations for individualizing the treatment approach for a given patient given the lack of general consensus of uniform recommendations for this patient population.

Abstract B125: Targeting translation for the treatment of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is currently the third leading cause of cancer deaths in the United States and is projected to be in second place by 2030. A key cellular aberration is the activating KRAS mutation (&gt;90%) which in turn leads to stabilizing the MYC oncoprotein and stimulating the growth of PDAC tumors. Dense stroma with elevated levels of hyaluronic acid is another characteristic of PDAC tumors contributing to poor therapeutic response. We describe a novel approach for the treatment of PDAC involving the targeting of thetranslation initiation factor 4A (eIF4A) with a new class of Pateamine A derivatives, DMDA PatA and MZ735.Our data show that nanomolar concentrations of these compounds inhibit cell proliferation and cause G0/G1 arrest in PDAC cell lines. We observed reduction of c-MYC, CyclinD1 and hyaluronic acid synthase HAS3 following treatment with eIF4A targeting compounds. RNA-seq analysis of Miapaca-2 cells treated with MZ735 using the Virtual Inference of Protein-activity by Enriched Regulon analysis (VIPER) algorithm revealed that loss of several MYC gene sets was among the most significantly altered compared to the control cells. We further performed proteomics to better define the consequences of MZ735-induced translation inhibition and observed that several key oncoproteins in PDAC were among the most depleted including MYC, CCND1, and EGFR. Finally, confocal imaging confirmed the reduction of hyaluronic acid in the eIF4A inhibitor-treated PDAC cells. We believe these small molecule compounds represent a new class of anticancer agents that have the potential to address both altered cellular and microenvironment components in PDAC.

Citation Format: Maryam Safari, Yu Ri Kim, Prabhjot S. Mundi, Changchun Deng, Susan E. Bates. Targeting translation for the treatment of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B125. doi:10.1158/1535-7163.TARG-19-B125