Berzosertib Plus Topotecan vs Topotecan Alone in Patients With Relapsed Small Cell Lung Cancer: A Randomized Clinical Trial

Importance

Patients with relapsed small cell lung cancer (SCLC), a high replication stress tumor, have poor prognoses and few therapeutic options. A phase 2 study showed antitumor activity with the addition of the ataxia telangiectasia and Rad3-related kinase inhibitor berzosertib to topotecan.

Objective

To investigate whether the addition of berzosertib to topotecan improves clinical outcomes for patients with relapsed SCLC.

Design, Setting, and Participants

Between December 1, 2019, and December 31, 2022, this open-label phase 2 randomized clinical trial recruited 60 patients with SCLC and relapse after 1 or more prior therapies from 16 US cancer centers. Patients previously treated with topotecan were not eligible.

Interventions

Eligible patients were randomly assigned to receive topotecan alone (group 1), 1.25 mg/m2 intravenously on days 1 through 5, or with berzosertib (group 2), 210 mg/m2 intravenously on days 2 and 5, in 21-day cycles. Randomization was stratified by tumor sensitivity to first-line platinum-based chemotherapy.

Main Outcomes and Measures

The primary end point was progression-free survival (PFS) in the intention-to-treat population. Secondary end points included overall survival (OS) in the overall population and among patients with platinum-sensitive or platinum-resistant tumors. The PFS and OS for each treatment group were estimated using the Kaplan-Meier method. The log-rank test was used to compare PFS and OS between the 2 groups, and Cox proportional hazards models were used to estimate the treatment hazard ratios (HRs) and the corresponding 2-sided 95% CI.

Results

Of 60 patients (median [range] age, 59 [34-79] years; 33 [55%] male) included in this study, 20 were randomly assigned to receive topotecan alone and 40 to receive a combination of topotecan with berzosertib. After a median (IQR) follow-up of 21.3 (18.1-28.3) months, there was no difference in PFS between the 2 groups (median, 3.0 [95% CI, 1.2-5.1] months for group 1 vs 3.9 [95% CI, 2.8-4.6] months for group 2; HR, 0.80 [95% CI, 0.46-1.41]; P = .44). Overall survival was significantly longer with the combination therapy (5.4 [95% CI, 3.2-6.8] months vs 8.9 [95% CI, 4.8-11.4] months; HR, 0.53 [95% CI, 0.29-0.96], P = .03). Adverse event profiles were similar between the 2 groups (eg, grade 3 or 4 thrombocytopenia, 11 of 20 [55%] vs 20 of 40 [50%], and any grade nausea, 9 of 20 [45%] vs 14 of 40 [35%]).

Conclusions and Relevance

In this randomized clinical trial, treatment with berzosertib plus topotecan did not improve PFS compared with topotecan therapy alone among patients with relapsed SCLC. However, the combination treatment significantly improved OS.

Trial Registration

ClinicalTrials.gov Identifier: NCT03896503.

Repurposing the FDA-approved anthelmintic pyrvinium pamoate for pancreatic cancer treatment: study protocol for a phase I clinical trial in early-stage pancreatic ductal adenocarcinoma

BACKGROUND

Recent reports of the utilisation of pyrvinium pamoate (PP), an FDA-approved anti-helminth, have shown that it inhibits pancreatic ductal adenocarcinoma (PDAC) cell growth and proliferation in-vitro and in-vivo in preclinical models. Here, we report about an ongoing phase I open-label, single-arm, dose escalation clinical trial to determine the safety and tolerability of PP in PDAC surgical candidates.

METHODS AND ANALYSIS

In a 3+3 dose design, PP is initiated 3 days prior to surgery. The first three patients will be treated with the initial dose of PP at 5 mg/kg orally for 3 days prior to surgery. Dose doubling will be continued to a reach a maximum of 20 mg/kg orally for 3 days, if the previous two dosages (5 mg/kg and 10 mg/kg) were tolerated. Dose-limiting toxicity grade≥3 is used as the primary endpoint. The pharmacokinetic and pharmacodynamic (PK/PD) profile of PP and bioavailability in humans will be used as the secondary objective. Each participant will be monitored weekly for a total of 30 days from the final dose of PP for any side effects. The purpose of this clinical trial is to examine whether PP is safe and tolerable in patients with pancreatic cancer, as well as assess the drug's PK/PD profile in plasma and fatty tissue. Potential implications include the utilisation of PP in a synergistic manner with chemotherapeutics for the treatment of pancreatic cancer.

ETHICS AND DISSEMINATION

This study was approved by the Thomas Jefferson Institutional Review Board. The protocol number for this study is 20F.041 (Version 3.1 as of 27 October 2021). The data collected and analysed from this study will be used to present at local and national conferences, as well as, written into peer-reviewed manuscript publications.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT05055323.

Targeting Replication Stress and Chemotherapy Resistance with a Combination of Sacituzumab Govitecan and Berzosertib: A Phase I Clinical Trial

PURPOSE

Despite promising preclinical studies, toxicities have precluded combinations of chemotherapy and DNA damage response (DDR) inhibitors. We hypothesized that tumor-targeted chemotherapy delivery might enable clinical translation of such combinations.

PATIENTS AND METHODS

In a phase I trial, we combined sacituzumab govitecan, antibody-drug conjugate (ADC) that delivers topoisomerase-1 inhibitor SN-38 to tumors expressing Trop-2, with ataxia telangiectasia and Rad3-related (ATR) inhibitor berzosertib. Twelve patients were enrolled across three dose levels.

RESULTS

Treatment was well tolerated, with improved safety over conventional chemotherapy-based combinations, allowing escalation to the highest dose. No dose-limiting toxicities or clinically relevant ≥grade 4 adverse events occurred. Tumor regressions were observed in 2 patients with neuroendocrine prostate cancer, and a patient with small cell lung cancer transformed from EGFR-mutant non-small cell lung cancer.

CONCLUSIONS

ADC-based delivery of cytotoxic payloads represents a new paradigm to increase efficacy of DDR inhibitors. See related commentary by Berg and Choudhury, p. 3557.

ATR inhibition augments the efficacy of lurbinectedin in small-cell lung cancer

Small-cell lung cancer (SCLC) is the most lethal type of lung cancer. Specifically, MYC-driven non-neuroendocrine SCLC is particularly resistant to standard therapies. Lurbinectedin was recently approved for the treatment of relapsed SCLC, but combinatorial approaches are needed to increase the depth and duration of responses to lurbinectedin. Using high-throughput screens, we found inhibitors of ataxia telangiectasia mutated and rad3 related (ATR) as the most effective agents for augmenting lurbinectedin efficacy. First-in-class ATR inhibitor berzosertib synergized with lurbinectedin in multiple SCLC cell lines, organoid, and in vivo models. Mechanistically, ATR inhibition abrogated S-phase arrest induced by lurbinectedin and forced cell cycle progression causing mitotic catastrophe and cell death. High CDKN1A/p21 expression was associated with decreased synergy due to G1 arrest, while increased levels of ERCC5/XPG were predictive of increased combination efficacy. Importantly, MYC-driven non-neuroendocrine tumors which are resistant to first-line therapies show reduced CDKN1A/p21 expression and increased ERCC5/XPG indicating they are primed for response to lurbinectedin-berzosertib combination. The combination is being assessed in a clinical trial NCT04802174.

A Novel 3DNA® Nanocarrier effectively delivers payloads to pancreatic tumors

INTRODUCTION

Standard-of-care systemic chemotherapies for pancreatic ductal adenocarcinoma (PDAC) currently have limited clinical benefits, in addition to causing adverse side effects in many patients. One factor known to contribute to the poor chemotherapy response is the poor drug diffusion into PDAC tumors. Novel treatment methods are therefore drastically needed to improve targeted delivery of treatments. Here, we evaluated the efficacy of the 3DNA® Nanocarrier (3DNA) platform to direct delivery of therapeutics to PDAC tumors in vivo.

MATERIALS AND METHODS

A panel of PDAC cell lines and a patient tissue microarray were screened for established tumor-specific proteins to identify targeting moieties for active targeting of the 3DNA. NRG mice with or without orthotopic MIA PaCa-2-luciferase PDAC tumors were treated intraperitoneally with 100 μl of fluorescently labeled 3DNA.

RESULTS

Folic acid and transferrin receptors were significantly elevated in PDAC compared to normal pancreas. Accordingly, both folic acid- and transferrin-conjugated 3DNA treatments significantly increased delivery of 3DNA specifically to tumors in comparison to unconjugated 3DNA treatment. In the absence of tumors, there was an increased clearance of both folic acid-conjugated 3DNA and unconjugated 3DNA, compared to the clearance rate in tumor-bearing mice. Lastly, delivery of siLuciferase by folic acid-conjugated 3DNA in an orthotopic model of luciferase-expressing PDAC showed significant and prolonged suppression of luciferase protein expression and activity.

CONCLUSION

Our study progresses the 3DNA technology as a reliable and effective treatment delivery platform for targeted therapeutic approaches in PDAC.

Extrachromosomal DNA Amplification Contributes to Small Cell Lung Cancer Heterogeneity and Is Associated with Worse Outcomes

Small-cell lung cancer (SCLC) is an aggressive neuroendocrine lung cancer. Oncogenic MYC amplifications drive SCLC heterogeneity, but the genetic mechanisms of MYC amplification and phenotypic plasticity, characterized by neuroendocrine and nonneuroendocrine cell states, are not known. Here, we integrate whole-genome sequencing, long-range optical mapping, single-cell DNA sequencing, and fluorescence in situ hybridization to find extrachromosomal DNA (ecDNA) as a primary source of SCLC oncogene amplifications and driver fusions. ecDNAs bring to proximity enhancer elements and oncogenes, creating SCLC transcription-amplifying units, driving exceptionally high MYC gene dosage. We demonstrate that cell-free nucleosome profiling can noninvasively detect ecDNA amplifications in plasma, facilitating its genome-wide interrogation in SCLC and other cancers. Altogether, our work provides the first comprehensive map of SCLC ecDNA and describes a new mechanism that governs MYC-driven SCLC heterogeneity. ecDNA-enabled transcriptional flexibility may explain the significantly worse survival outcomes of SCLC harboring complex ecDNA amplifications.

SIGNIFICANCE

MYC drives SCLC progression, but the genetic basis of MYC-driven SCLC evolution is unknown. Using SCLC as a paradigm, we report how ecDNA amplifications function as MYC-amplifying units, fostering tumor plasticity and a high degree of tumor heterogeneity. This article is highlighted in the In This Issue feature, p. 799.

The RNA-Binding Protein HuR Posttranscriptionally Regulates the Protumorigenic Activator YAP1 in Pancreatic Ductal Adenocarcinoma

Yes-associated protein 1 (YAP1) is indispensable for the development of mutant KRAS-driven pancreatic ductal adenocarcinoma (PDAC). High YAP1 mRNA is a prognostic marker for worse overall survival in patient samples; however, the regulatory mechanisms that mediate its overexpression are not well understood. YAP1 genetic alterations are rare in PDAC, suggesting that its dysregulation is likely not due to genetic events. HuR is an RNA-binding protein whose inhibition impacts many cancer-associated pathways, including the "conserved YAP1 signature" as demonstrated by gene set enrichment analysis. Screening publicly available and internal ribonucleoprotein immunoprecipitation (RNP-IP) RNA sequencing (RNA-Seq) data sets, we discovered that YAP1 is a high-confidence target, which was validated in vitro with independent RNP-IPs and 3' untranslated region (UTR) binding assays. In accordance with our RNA sequencing analysis, transient inhibition (e.g., small interfering RNA [siRNA] and small-molecular inhibition) and CRISPR knockout of HuR significantly reduced expression of YAP1 and its transcriptional targets. We used these data to develop a HuR activity signature (HAS), in which high expression predicts significantly worse overall and disease-free survival in patient samples. Importantly, the signature strongly correlates with YAP1 mRNA expression. These findings highlight a novel mechanism of YAP1 regulation, which may explain how tumor cells maintain YAP1 mRNA expression at dynamic times during pancreatic tumorigenesis.

Abstract 1811: Dithiazanine Iodide suppresses mitochondrial function to strongly inhibit pancreatic ductal adenocarcinoma growth in-vitro and in-vivo, producing a marked increase in survival

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive recalcitrant cancer with a uniquely austere tumor microenvironment (TME). It is hypovascularized, hypoxic, and poor in nutrients. These features, which are critical due to the increased energetic demand in continuously replicating cancer cells, drive metabolic reprograming to support the continued activity. Thus leading to a vulnerability in the form of energy restriction - a vulnerability further exacerbated by the nutrient-poor pancreatic cancer TME. We have recently shown mitochondrial inhibition to have great potential in in-vitro inhibition of PDAC cells. Since repurposing of FDA-approved drugs holds great promise in terms of faster and safer drug development, we selected to investigate the effect of mitochondrial inhibition on pancreatic cancer cells through assessment of the previously FDA-approved antimicrobial Dithiazanine Iodide (CDI). CDI is a fluorescent, orally bioavailable, small molecule. In-vitro, it has been previously shown to preferentially localize to the mitochondria, bind proteins and nucleic acids, and have a yet to be discerned inhibitory effect on the electron transport chain. We demonstrated CDI had low IC50s (30-300 nM) in multiple PDAC and other GI cancer cell lines. In an agnostic, unbiased manner, we assessed metabolomic and transcriptomic perturbations caused by CDI. These revealed a profound 92% decrease in the abundance of mitochondrial-encoded transcripts (P<0.05), decreased mitochondrial beta-oxidation, and a reduction in the ATP/ADP ratio. We have therefore hypothesized that the anti-cancer effects of CDI may be related to disruption of mitochondrial processes and we proceeded to characterize its mechanism of action. CDI treatment reduced protein expression of electron transport chain complexes I, II, III, and IV. Treatment with CDI in hypoglycemic conditions resulted in a 3-4 fold increase in sensitivity (P<0.05) and ATP quantification showed a marked >90% decrease in cellular ATP (P<0.05). Furthermore, mitochondria-depleted PDAC cell lines were 4-fold more resistant to CDI treatment (P<0.05). In-vivo, oral CDI treatment resulted in a 2-fold decrease in mouse xenograft tumor growth compared to gemcitabine treatment. RNA-sequencing from the in-vivo samples showed a 60% reduction in the abundance of mitochondrial-encoded transcripts (P<0.05). Examination of the mitochondrial sequences revealed the existence of putative G-Quadruplex sequences. Fluorescence shift and stop-PCR assays confirmed CDI to be a G-Quadruplex binder of mitochondrial sequences.

Citation Format: Avinoam Nevler, Christopher W. Schultz, Aditi Jain, Saed Khalilieh, Grace McCarthy, Harish Lavu, Wilbur Bowne, Charles J. Yeo, Jonathan R. Brody. Dithiazanine Iodide suppresses mitochondrial function to strongly inhibit pancreatic ductal adenocarcinoma growth in-vitro and in-vivo, producing a marked increase in survival [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 1811.

Replication stress defines distinct molecular subtypes across cancers

Endogenous replication stress is a major driver of genomic instability. Current assessments of replication stress are low throughput precluding its comprehensive assessment across tumors. Here we develop and validate a transcriptional profile of replication stress by leveraging established cellular characteristics that portend replication stress. The repstress gene signature defines a subset of tumors across lineages characterized by activated oncogenes, aneuploidy, extrachromosomal DNA amplification, immune evasion, high genomic instability, and poor survival, and importantly predicts response to agents targeting replication stress more robustly than previously reported transcriptomic measures of replication stress. Repstress score profiles the dual roles of replication stress during tumorigenesis and in established cancers and defines distinct molecular subtypes within cancers that may be more vulnerable to drugs targeting this dependency. Altogether, our study provides a molecular profile of replication stress, providing novel biological insights of the replication stress phenotype, with clinical implications.

Heterogeneity of neuroendocrine transcriptional states in metastatic small cell lung cancers and patient-derived models

Molecular subtypes of small cell lung cancer (SCLC) defined by the expression of key transcription regulators have recently been proposed in cell lines and limited number of primary tumors. The clinical and biological implications of neuroendocrine (NE) subtypes in metastatic SCLC, and the extent to which they vary within and between patient tumors and in patient-derived models is not known. We integrate histology, transcriptome, exome, and treatment outcomes of SCLC from a range of metastatic sites, revealing complex intra- and intertumoral heterogeneity of NE differentiation. Transcriptomic analysis confirms previously described subtypes based on ASCL1, NEUROD1, POU2F3, YAP1, and ATOH1 expression, and reveal a clinical subtype with hybrid NE and non-NE phenotypes, marked by chemotherapy-resistance and exceedingly poor outcomes. NE tumors are more likely to have RB1, NOTCH, and chromatin modifier gene mutations, upregulation of DNA damage response genes, and are more likely to respond to replication stress targeted therapies. In contrast, patients preferentially benefited from immunotherapy if their tumors were non-NE. Transcriptional phenotypes strongly skew towards the NE state in patient-derived model systems, an observation that was confirmed in paired patient-matched tumors and xenografts. We provide a framework that unifies transcriptomic and genomic dimensions of metastatic SCLC. The marked differences in transcriptional diversity between patient tumors and model systems are likely to have implications in development of novel therapeutic agents.

The FDA-Approved Anthelmintic Pyrvinium Pamoate Inhibits Pancreatic Cancer Cells in Nutrient-Depleted Conditions by Targeting the Mitochondria

Pancreatic ductal adenocarcinoma (PDAC) is a lethal aggressive cancer, in part due to elements of the microenvironment (hypoxia, hypoglycemia) that cause metabolic network alterations. The FDA-approved antihelminthic pyrvinium pamoate (PP) has previously been shown to cause PDAC cell death, although the mechanism has not been fully determined. We demonstrated that PP effectively inhibited PDAC cell viability with nanomolar IC50 values (9-93 nmol/L) against a panel of PDAC, patient-derived, and murine organoid cell lines. In vivo, we demonstrated that PP inhibited PDAC xenograft tumor growth with both intraperitoneal (IP; P < 0.0001) and oral administration (PO; P = 0.0023) of human-grade drug. Metabolomic and phosphoproteomic data identified that PP potently inhibited PDAC mitochondrial pathways including oxidative phosphorylation and fatty acid metabolism. As PP treatment reduced oxidative phosphorylation (P < 0.001), leading to an increase in glycolysis (P < 0.001), PP was 16.2-fold more effective in hypoglycemic conditions similar to those seen in PDAC tumors. RNA sequencing demonstrated that PP caused a decrease in mitochondrial RNA expression, an effect that was not observed with established mitochondrial inhibitors rotenone and oligomycin. Mechanistically, we determined that PP selectively bound mitochondrial G-quadruplexes and inhibited mitochondrial RNA transcription in a G-quadruplex-dependent manner. This subsequently led to a 90% reduction in mitochondrial encoded gene expression. We are preparing to evaluate the efficacy of PP in PDAC in an IRB-approved window-of-opportunity trial (IND:144822).

Novel and Highly Potent ATR Inhibitor M4344 Kills Cancer Cells With Replication Stress, and Enhances the Chemotherapeutic Activity of Widely Used DNA Damaging Agents

Although several ATR inhibitors are in development, there are unresolved questions regarding their differential potency, molecular signatures of patients with cancer for predicting activity, and most effective therapeutic combinations. Here, we elucidate how to improve ATR-based chemotherapy with the newly developed ATR inhibitor, M4344 using in vitro and in vivo models. The potency of M4344 was compared with the clinically developed ATR inhibitors BAY1895344, berzosertib, and ceralasertib. The anticancer activity of M4344 was investigated as monotherapy and combination with clinical DNA damaging agents in multiple cancer cell lines, patient-derived tumor organoids, and mouse xenograft models. We also elucidated the anticancer mechanisms and potential biomarkers for M4344. We demonstrate that M4344 is highly potent among the clinically developed ATR inhibitors. Replication stress (RepStress) and neuroendocrine (NE) gene expression signatures are significantly associated with a response to M4344 treatment. M4344 kills cancer cells by inducing cellular catastrophe and DNA damage. M4344 is highly synergistic with a broad range of DNA-targeting anticancer agents. It significantly synergizes with topotecan and irinotecan in patient-derived tumor organoids and xenograft models. Taken together, M4344 is a promising and highly potent ATR inhibitor. It enhances the activity of clinical DNA damaging agents commonly used in cancer treatment including topoisomerase inhibitors, gemcitabine, cisplatin, and talazoparib. RepStress and NE gene expression signatures can be exploited as predictive markers for M4344.

Therapeutic targeting of ATR yields durable regressions in small cell lung cancers with high replication stress

Small cell neuroendocrine cancers (SCNCs) are recalcitrant cancers arising from diverse primary sites that lack effective treatments. Using chemical genetic screens, we identified inhibition of ataxia telangiectasia and rad3 related (ATR), the primary activator of the replication stress response, and topoisomerase I (TOP1), nuclear enzyme that suppresses genomic instability, as synergistically cytotoxic in small cell lung cancer (SCLC). In a proof-of-concept study, we combined M6620 (berzosertib), first-in-class ATR inhibitor, and TOP1 inhibitor topotecan in patients with relapsed SCNCs. Objective response rate among patients with SCLC was 36% (9/25), achieving the primary efficacy endpoint. Durable tumor regressions were observed in patients with platinum-resistant SCNCs, typically fatal within weeks of recurrence. SCNCs with high neuroendocrine differentiation, characterized by enhanced replication stress, were more likely to respond. These findings highlight replication stress as a potentially transformative vulnerability of SCNCs, paving the way for rational patient selection in these cancers, now treated as a single disease.

Selecting the optimal parameters for sonoporation of pancreatic cancer in a pre-clinical model

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in the modern world, in part due to poor delivery of chemotherapeutics. Sonoporation can be used to enhance the efficacy of standard of care therapies for PDAC. Using xenograft models of PDAC we investigate sonoporation using four ifferent ultrasound contrast agents (UCAs) and two ultrasound regimens to identify the ideal parameters to increase therapeutic efficacy. MIA-PaCa2 xenografts in over 175 immunodeficient mice were treated with gemcitabine and paclitaxel and subjected to low or high power ultrasound (60 and 200 mW/cm² respectively) in conjunction with one of four different UCAs. The UCAs investigated were Definity®, SonoVue®, Optison™ or Sonazoid™. Tumor volumes, vascularity, hemoglobin, and oxygenation were measured and compared to controls. High power treatment in conjunction with Sonazoid sonoporation led to significantly smaller tumors when started early (tumors ~50mm³; p = .0105), while no UCAs significantly increased efficacy in the low power cohort. This trend was also found in larger tumors (~250mm³) where all four UCA agents significantly increased therapeutic efficacy in the high power group (p < .01), while only Definity and SonoVue increased efficacy in the low power cohort (p < .03). Overall, the higher power ultrasound treatment modality was more consistently effective at decreasing tumor volume and increasing vascularity characteristics. In conclusion, Sonazoid was the most consistently effective UCA at decreasing tumor volume and increasing vascularity. Thus, we are pursuing a larger phase II clinical trial to validate the increased efficacy of sonoporation in conjunction with chemotherapy in PDAC patients.

HuR/ELAVL1 drives malignant peripheral nerve sheath tumor growth and metastasis

Cancer cells can develop a strong addiction to discrete molecular regulators, which control the aberrant gene expression programs that drive and maintain the cancer phenotype. Here, we report the identification of the RNA-binding protein HuR/ELAVL1 as a central oncogenic driver for malignant peripheral nerve sheath tumors (MPNSTs), which are highly aggressive sarcomas that originate from cells of the Schwann cell lineage. HuR was found to be highly elevated and bound to a multitude of cancer-associated transcripts in human MPNST samples. Accordingly, genetic and pharmacological inhibition of HuR had potent cytostatic and cytotoxic effects on tumor growth, and strongly suppressed metastatic capacity in vivo. Importantly, we linked the profound tumorigenic function of HuR to its ability to simultaneously regulate multiple essential oncogenic pathways in MPNST cells, including the Wnt/β-catenin, YAP/TAZ, RB/E2F, and BET pathways, which converge on key transcriptional networks. Given the exceptional dependency of MPNST cells on HuR for survival, proliferation, and dissemination, we propose that HuR represents a promising therapeutic target for MPNST treatment.

Splenic-vasculature involvement is associated with poor prognosis in resected distal pancreatic cancer

Background

Distal pancreatic carcinoma is one of the most lethal cancers largely due to its high incidence of distant metastasis. This study aims to assess the prognostic value of splenic-vasculature involvement in resected distal pancreatic carcinoma.

Methods

In this retrospective study, we collected the clinicopathologic information of 454 patients with pancreatic cancer and performed univariate and multivariate analyses to identify factors associated with progression-free survival (PFS) and overall survival (OS), with an emphasis on the prognostic value of splenic-artery and -vein involvement.

Results

Univariate analysis revealed that larger tumor size, non-intraductal papillary mucinous neoplasm (non-IPMN)-associated adenocarcinoma, poor differentiation, stage pT3, nodal metastasis, lymphovascular invasion, perineural invasion, and pathologic and radiographic evidence of splenic-vein invasion were significantly associated with shorter PFS and OS (all P < 0.05). Multivariate analysis confirmed non-IPMN-associated adenocarcinoma, stage pT3, stage pN1–2, and post-operative adjuvant chemotherapy as independent risk factors for both PFS and OS, and larger tumor size and radiographic evidence of splenic-artery invasion as predictors of PFS only.

Conclusion

Guidelines should be developed for a uniform approach with regard to the examination and reporting of the status of the splenic vasculature when dealing with distal-pancreatic-cancer specimens.

Margin-Positive Pancreatic Ductal Adenocarcinoma during Pancreaticoduodenectomy: Additional Resection Does Not Improve Survival

BACKGROUND

The impact of resecting positive margins during pancreaticoduodenectomy (PD) for pancreatic ductal adenocarcinoma (PDA) remains debated. Additionally, the survival benefit of resecting multiple positive margins is unknown.

METHODS

We identified patients with PDA who underwent PD from 2006 to 2015. Pancreatic neck, bile duct, and uncinate frozen section margins were assessed before and after resection of positive margins. Survival curves were compared with log-rank tests. Multivariable Cox regression assessed the effect of margin status on overall survival.

RESULTS

Of 501 patients identified, 17.3%, 5.3%, and 19.7% had an initially positive uncinate, bile duct, or neck margin, respectively. Among initially positive bile duct and neck margins, 77.8% and 67.0% were resected, respectively. Although median survival was decreased among patients with any positive margins (15.6 vs. 20.9 months; p = 0.006), it was similar among patients with positive bile duct or neck margins with or without R1 to R0 resection (17.0 vs. 15.6 months; p = 0.20). Median survival with and without positive uncinate margins was 13.8 vs. 19.7 months (p = 0.04). Uncinate margins were never resected. Resection of additional margins when the uncinate was concurrently positive was not associated with improved survival (p = 0.37). Patients with positive margins who received adjuvant therapy had improved survival, regardless of margin resection (p = 0.03). Adjuvant therapy was independently protective against death (hazard ratio 0.6, 95% CI 0.5-0.7).

CONCLUSIONS

Positive PD margins at any position are associated with reduced overall survival; however, resection of additional margins may not improve survival, particularly with concurrently positive uncinate margins. Adjuvant chemotherapy improves survival with positive margins, regardless of resection.

Abstract B45: A feedback gene regulatory mechanism between YAP1 and the RNA-binding protein, Human Antigen R (HuR), in pancreatic cancer cells: Implications for a context-dependent pancreatic cancer cell survival network

Pancreatic ductal adenocarcinoma (PDAC) is the third-leading cause of cancer-related death in the U.S. In roughly 95% of cases, gain-of-function mutations in KRAS combine with loss of tumor suppressors to progress preinvasive neoplasms (PanINs) to late-stage ductal adenocarcinoma. Two important facilitators of KRAS function, Human Antigen R (HuR) and Yes-associated protein 1 (YAP1), are both highly overexpressed in PDAC. HuR is an RNA-binding protein that facilitates gene expression through the stabilization and increased translation of target prosurvival mRNAs upon stress. YAP1 is a transcriptional coactivator, which associates with a number of transcription factor families to sense and upregulate targets that lead to tumor growth and cellular crosstalk. While the functions of HuR and YAP1 are well known, the events that lead to their overexpression and regulation are poorly understood.

Our previous work has shown that overexpression of cytoplasmic HuR correlates strongly with tumor staging. Low levels of HuR correspond to early PanINs with staining steadily increasing in late-stage PanIN lesions and gross overexpression in invasive adenocarcinoma. Conversely, YAP1 overexpression seems to be most critical for initial development and expansion of the tumor cells, while it converts to a maintenance role once PDAC is fully developed. Ongoing studies will address whether the temporal regulation of these proteins could explain their overexpression patterns in pancreatic pathologic stages as they relate to cooperating with KRAS activity.

YAP1 was first identified as a HuR target via ribonucleoprotein-immunoprecipitation assays in which HuR-bound mRNAs were run on a whole-transcriptome microarray. YAP1 mRNA was significantly bound to HuR as compared to the IgG isotype control (13.2-fold) and was in line with previously established mRNA targets (WEE1, 3.2-fold; PIM1, 13.9-fold). YAP1 mRNA bound to HuR is abolished when treated with a known HuR inhibitor, pyrvinium pamoate, even in the presence of an established HuR stressor (i.e., oxaliplatin). Actinomycin D chase assays demonstrated that YAP1 mRNA stability is significantly dependent on HuR proficiency. We validated that both YAP1 mRNA and protein expression levels are dependent on HuR via real-time quantitative PCR and Western blot analysis. Impact of YAP1 transcriptional activity was evaluated both by measuring total expression of canonical YAP targets (i.e., CTGF and CYR61) and by using a TEAD reporter construct (i.e., 8xGTIIC). Surprisingly, we found that RNA silencing of YAP1 significantly reduced HuR mRNA and protein expression, as well as established HuR targets, WEE1 and PIM1. Treatment with small-molecule inhibitors verteporfin and CA3, which target the interface of YAP1’s transcription-factor binding domain, recapitulated these effects in a dose- and time-dependent manner. We are currently cloning HuR’s promoter region into a luciferase reporter in order to evaluate the impact of YAP1 on HuR transcriptional expression.

Citation Format: Samantha Z. Brown, Christopher W. Schultz, Avinoam Nevler, Tianyun Li, Aditi Jain, Raymond O’Neil, Wei Jiang, Eric Londin, Dan A. Dixon, Liang Xu, Charles J. Yeo, Jonathan R. Brody. A feedback gene regulatory mechanism between YAP1 and the RNA-binding protein, Human Antigen R (HuR), in pancreatic cancer cells: Implications for a context-dependent pancreatic cancer cell survival network [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B45.

Validation of American Joint Committee on Cancer 8th edition of TNM staging in resected distal pancreatic cancer

BACKGROUND

In order to improve risk stratification and clinical management of the pancreatic ductal adenocarcinoma (PDAC), the American Joint Committee on Cancer (AJCC) has published its eighth edition staging manual. Some major changes have been introduced in the new staging system for both T and N categories. Given the rarity of resectable disease, distal pancreatic cancer is likely underrepresented in the published clinical studies, and how the impact of the staging system actually reflects on to clinical outcomes remain unclear.

AIM

To validate the AJCC 8^th edition of TNM staging in distal PDAC.

METHODS

A retrospective cohort study was performed in seven academic medical centers in the United States. Clinicopathological prognostic factors associated with progression-free survival (PFS) and overall survival (OS) were evaluated through univariate and multivariate analyses.

RESULTS

Overall, 454 patients were enrolled in the study, and were divided into 2 subgroups: Invasive intraductal papillary mucinous neoplasms (IPMN) (115 cases) and non-IPMN associated adenocarcinoma (339 cases). Compared to invasive IPMN, non-IPMN associated adenocarcinomas are more common in relatively younger patients, have larger tumor size, are more likely to have positive lymph nodes, and are associated with a higher tumor (T) stage and nodal (N) stage, lymphovascular invasion, perineural invasion, tumor recurrence, and a worse PFS and OS. The cohort was predominantly categorized as stage 3 per AJCC 7^th edition staging manual, and it’s more evenly distributed based on 8^th edition staging manual. T and N staging of both 7^th and 8^th edition sufficiently stratify PFS and OS in the entire cohort, although dividing into N1 and N2 according to the 8^th edition does not show additional stratification. For PDAC arising in IPMN, T staging of the 7^th edition and N1/N2 staging of the 8^th edition appear to further stratify PFS and OS. For PDAC without an IPMN component, T staging from both versions fails to stratify PFS and OS.

CONCLUSION

The AJCC 8^th edition TNM staging system provides even distribution for the T staging, however, it does not provide better risk stratification than previous staging system for distal pancreatic cancer.

ATM Dysfunction in Pancreatic Adenocarcinoma and Associated Therapeutic Implications

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal solid malignancies with very few therapeutic options to treat advanced or metastatic disease. The utilization of genomic sequencing has identified therapeutically relevant alterations in approximately 25% of PDAC patients, most notably in the DNA damage response and repair (DDR) genes, rendering cancer cells more sensitive to DNA-damaging agents and to DNA damage response inhibitors, such as PARP inhibitors. ATM is one of the most commonly mutated DDR genes, with somatic mutations identified in 2% to 18% of PDACs and germline mutations identified in 1% to 34% of PDACs. ATM plays a complex role as a cell-cycle checkpoint kinase, regulator of a wide array of downstream proteins, and responder to DNA damage for genome stability. The disruption of ATM signaling leads to downstream reliance on ATR and CHK1, among other DNA-repair mechanisms, which may enable exploiting the inhibition of downstream proteins as therapeutic targets in ATM-mutated PDACs. In this review, we detail the function of ATM, review the current data on ATM deficiency in PDAC, examine the therapeutic implications of ATM alterations, and explore the current clinical trials surrounding the ATM pathway.

Effect of Hypercapnia, an Element of Obstructive Respiratory Disorder, on Pancreatic Cancer Chemoresistance and Progression

BACKGROUND

Chronic obstructive respiratory disorders (ORDs) are linked to increased rates of cancer-related deaths. Little is known about the effects of hypercapnia (elevated CO₂) on development of pancreatic ductal adenocarcinoma (PDAC) and drug resistance.

STUDY DESIGN

Two PDAC cell lines were exposed to normocapnic (5% CO₂) and hypercapnic (continuous/intermittent 10% CO₂) conditions, physiologically similar to patients with active ORD. Cells were assessed for proliferation rate, colony formation, and chemo-/radiotherapeutic efficacy. In a retrospective clinical study design, patients with PDAC who had undergone pancreatic resection between 2002 and 2014 were reviewed. Active smokers were excluded to remove possible smoking-related protumorigenic influence. Clinical data, pathologic findings, and survival end points were recorded. Kaplan-Meier and Cox regression analyses were performed.

RESULTS

Exposure to hypercapnia resulted in increased colony formation and proliferation rates in vitro in both cell lines (MIA-PaCa-2: 111% increase and Panc-1: 114% increase; p < 0.05). Hypercapnia exposure induced a 2.5-fold increase in oxaliplatin resistance (p < 0.05) in both cell lines and increased resistance to ionizing radiation in MIA-PaCa-2 cells (p < 0.05). Five hundred and seventy-eight patients were included (52% were male, median age was 68.7 years [interquartile range 60.6 to 76.8 years]). Cox regression analysis, assessing TNM staging, age, sex, and ORD status, identified ORD as an independent risk factor for both overall survival (hazard ratio 1.64; 95% CI, 1.2 to 2.3; p < 0.05) and disease-free survival (hazard ratio 1.68; 95% CI, 1.06 to 2.67).

CONCLUSIONS

PDAC cells exposed to hypercapnic environments, which is common in patients with ORD, showed tumor proliferation, radioresistance, and chemoresistance. Patients with a history of ORD had a worse overall prognosis, suggesting that hypercapnic conditions play a role in the development and progression of PDAC and stressing the need for patient-tailored care.

Understanding and targeting the disease-related RNA binding protein human antigen R (HuR)

Altered gene expression is a characteristic feature of many disease states such as tumorigenesis, and in most cancers, it facilitates cancer cell survival and adaptation. Alterations in global gene expression are strongly impacted by post-transcriptional gene regulation. The RNA binding protein (RBP) HuR (ELAVL1) is an established regulator of post-transcriptional gene regulation and is overexpressed in most human cancers. In many cancerous settings, HuR is not only overexpressed, but it is "overactive" as denoted by increased subcellular localization within the cytoplasm. This dysregulation of HuR expression and cytoplasmic localization allows HuR to stabilize and increase the translation of various prosurvival messenger RNA (mRNAs) involved in the pathogenesis of numerous cancers and various diseases. Based on almost 20 years of work, HuR is now recognized as a therapeutic target. Herein, we will review the role HuR plays in the pathophysiology of different diseases and ongoing therapeutic strategies to target HuR. We will focus on three ongoing-targeted strategies: (1) inhibiting HuR's translocation from the nucleus to the cytoplasm; (2) inhibiting the ability of HuR to bind target RNA; and (3) silencing HuR expression levels. In an oncologic setting, HuR has been demonstrated to be critical for a cancer cell's ability to survive a variety of cancer relevant stressors (including drugs and elements of the tumor microenvironment) and targeting this protein has been shown to sensitize cancer cells further to insult. We strongly believe that targeting HuR could be a powerful therapeutic target to treat different diseases, particularly cancer, in the near future. This article is categorized under: RNA in Disease and Development > RNA in Disease NRA Turnover and Surveillance > Regulation of RNA Stability Translation > Translation Regulation.

Poly (ADP) Ribose Glycohydrolase Can Be Effectively Targeted in Pancreatic Cancer

Patients with metastatic pancreatic ductal adenocarcinoma (PDAC) have an average survival of less than 1 year, underscoring the importance of evaluating novel targets with matched targeted agents. We recently identified that poly (ADP) ribose glycohydrolase (PARG) is a strong candidate target due to its dependence on the pro-oncogenic mRNA stability factor HuR (ELAVL1). Here, we evaluated PARG as a target in PDAC models using both genetic silencing of PARG and established small-molecule PARG inhibitors (PARGi), PDDX-01/04. Homologous repair-deficient cells compared with homologous repair-proficient cells were more sensitive to PARGi in vitro. In vivo, silencing of PARG significantly decreased tumor growth. PARGi synergized with DNA-damaging agents (i.e., oxaliplatin and 5-fluorouracil), but not with PARPi therapy. Mechanistically, combined PARGi and oxaliplatin treatment led to persistence of detrimental PARylation, increased expression of cleaved caspase-3, and increased γH2AX foci. In summary, these data validate PARG as a relevant target in PDAC and establish current therapies that synergize with PARGi. SIGNIFICANCE: PARG is a potential target in pancreatic cancer as a single-agent anticancer therapy or in combination with current standard of care.

Abemaciclib Is Effective Against Pancreatic Cancer Cells and Synergizes with HuR and YAP1 Inhibition

Mutation or promoter hypermethylation of CDKN2A is found in over 90% of pancreatic ductal adenocarcinomas (PDAC) and leads to loss of function of cell-cycle inhibitors p16 (INK4A) and p14 (ARF) resulting in unchecked proliferation. The CDK4/6 inhibitor, abemaciclib, has nanomolar IC₅₀s in PDAC cell lines and decreases growth through inhibition of phospho-Rb (pRb), G₁ cell-cycle arrest, apoptosis, and the senescent phenotype detected with β-galactosidase staining and relevant mRNA elevations. Daily abemaciclib treatments in mouse PDAC xenograft studies were safe and demonstrated a 3.2-fold decrease in tumor volume compared with no treatment (P < 0.0001) accompanying a decrease in both pRb and Ki67. We determined that inhibitors of HuR (ELAVL1), a prosurvival mRNA stability factor that regulates cyclin D1, and an inhibitor of Yes-Associated Protein 1 (YAP1), a pro-oncogenic, transcriptional coactivator important for CDK6 and cyclin D1, were both synergistic with abemaciclib. Accordingly, siRNA oligonucleotides targeted against HuR, YAP1, and their common target cyclin D1, validated the synergy studies. In addition, we have seen increased sensitivity to abemaciclib in a PDAC cell line that harbors a loss of the ELAVL1 gene via CRISP-Cas9 technology. As an in vitro model for resistance, we investigated the effects of long-term abemaciclib exposure. PDAC cells chronically cultured with abemaciclib displayed a reduction in cellular growth rates (GR) and coresistance to gemcitabine and 5-fluorouracil (5-FU), but not to HuR or YAP1 inhibitors as compared with no treatment controls. We believe that our data provide compelling preclinical evidence for an abemaciclib combination-based clinical trial in patients with PDAC. IMPLICATIONS: Our data suggest that abemaciclib may be therapeutically relevant for the treatment in PDAC, especially as part of a combination regimen inhibiting YAP1 or HuR.

Abstract 3058: Recharacterizing the FDA approved drug pyrvinium pamoate as a clinically relevant HuR inhibitor in pancreatic ductal adenocarcinoma

HuR is an RNA binding protein involved in a coordinated cellular survival response to stressors. Upon insults such as chemotherapy, HuR translocates from the nucleus to the cytoplasm where it binds the 3’UTR of target mRNAs. HuR’s interaction with target mRNAs leads to the upregulation of target genes and ultimately treatment resistance. This is particularly relevant in the case of pancreatic ductal adenocarcinoma (PDA). PDA is highly resistant to radiotherapy and standard chemotherapy such as FOLFIRINOX or gemcitabine/nab-paclitaxel. Using a tumor microarray (TMA), we found 79% of patient tumor samples (n=70) were positive for active cytoplasmic HuR, while little to no cytoplasmic localization was detected in normal tissue. In addition, HuR CRISPR knockout cell lines have a xenograft lethal phenotype. The aim of our current study is to target HuR by re-purposing the anti-helminthic, FDA approved small molecule pyrvinium pamoate (PP) to inhibit HuR’s translocation and sensitize PDA cells to concurrent therapies. PP has been shown in bladder cancer to inhibit the translocation of HuR in vitro and in vivo. We have reproduced this in multiple PDA cell lines and have shown impressive drug potency with IC50s as low as 38nM in 2D cultures of PDA cell lines and PDX lines and 16nM in a 3D mouse PDA organoid model. We have demonstrated that inhibition of HuR translocation is likely to occur through secondary effectors AMPK and CDK1. We have also demonstrated that PP’s inhibition of HuR function may be through direct inhibition of target binding. In comparison to other published HuR inhibitors PP inhibits the binding of HuR to targets more potentlt with nanomolar IC50’s. We confirmed this work through HuR RNA Immunoprecipitation experiments and determined that PP inhibited the ability of HuR to bind target mRNA. We generated HuR deficient CRISPR lines to and demonstrated that lack of HuR sensitizes PDA cells to various therapeutics, an effect which is exacerbated in physiologically relevant low glucose settings. We next demonstrated that PP can synergize with several therapeutics including the CDK4/6 inhibitors Abemaciclib and Palbociclib in PDA cells and that this synergy is increased in low glucose setting. This synergistic effect is ameliorated in HuR deficient CRISPR cell lines, indicating that PP achieves this synergistic potential through the inhibition of HuR. We performed targeted phosphoproteomics and found that PP robustly inhibited critical mTOR pathway members as well as validating previous reports that it can inhibit the WNT pathway. Finally, we have demonstrated that PP has a dose dependent effect on PDA tumor growth in vivo with IP and PO dosing regimens. This work supports the recharacterization of PP as a potentially effective therapeutic agent for the treatment of PDA. Early phase clinical trials of PP in human subjects are being planned for 2019.

Citation Format: Christopher W. Schultz, Teena Dhir, Samantha Z. Brown, Saswati Chand, Wei Jiang, Grace A. McCarthy, Alex O. Haber, Charles J. Yeo, Austin Goetz, Avinoam Nevler, Oloruntoba Bolaji, Jonathan R. Brody. Recharacterizing the FDA approved drug pyrvinium pamoate as a clinically relevant HuR inhibitor in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3058.

Abstract 1961: Gaps in the armor: Targeting HuR to sensitize pancreatic cancer

HuR is an RNA binding protein involved in a coordinated cellular response to stressors. Upon insults such as chemotherapy or radiation treatment, HuR translocates from the nucleus to the cytoplasm where it binds the 3'UTR of target mRNAs. HuR's interaction with target mRNAs leads to the upregulation of target genes and ultimately treatment resistance. This is particularly relevant in the case of pancreatic ductal adenocarcinoma (PDA). PDA is highly resistant to standard chemotherapy such as FOLFIRINOX or gemcitabine/nab-paclitaxel. Using a tumor microarray (TMA), we found 79% of patient tumor samples (n=70) were positive for active cytoplasmic HuR, while little to no cytoplasmic localization was detected in normal tissue. In addition, HuR CRISPR knockout cell lines have a xenograft lethal phenotype. Previously published data also demonstrated that reduction of HuR in xenografts with a DOX-inducible shRNA system caused a 3.6 fold decrease in tumor size. HuR reduction was also shown to potentiate a PARP-inhibitor (olaparib) treatment from a 5.6-fold reduction alone to 9.3-fold reduction in tumor size when combined with shHuR, demonstrating the role of HuR in drug resistance. The aim of our current study was: A) to target HuR directly using nanoparticle delivery of siRNA against HuR; and B) to use the FDA approved small molecule pyrvinium pamoate (PP) to inhibit HuR's translocation and sensitize PDA cells to concurrent therapies. Using 3DNA, a 60nm nanoparticle composed of a sphere of crosslinked DNA, we have successfully delivered siRNA against HuR in vivo utilizing targeting moieties against receptors known to be overexpressed on the surface of PDA cells: EGFR, folic acid receptor, and transferrin receptor. Bi-weekly IP treatment of siHuR bound to 3DNA was safe and effective at extending life in a xenograft model as indicated by Kaplan Meier analysis (p=0.01). We are currently testing siHuR-3DNA dendrimer therapy's ability to sensitize PDA cells to oxaliplatin or olaparib in vivo. We are also investigating the use of PP to target HuR's localization. PP has previously been shown in bladder cancer to inhibit the translocation of HuR in vitro and in vivo. We have reproduced this finding in PDA cells, and have shown impressive drug potency with IC50s as low as 38nM in 2D cultures and 16nM in a 3D mouse PDA organoid model. Combination index (CI) values determine drugs interactions where 1 is additive, &lt;1 is synergistic and &gt;1 is antagonistic. We have determined that PP can enhance therapies such as gemcitabine (CI of 0.55), olaparib (CI of 0.40) and palbociclib (CI of 0.37) in vitro, and are currently validating these findings in vivo. Taken together, our data demonstrate that HuR inhibition via 3DNA delivery of siHuR and/or PP treatment can sensitize PDA cells to chemotherapy and targeted therapies. By inhibiting a resistance driver (HuR) in pancreatic cancer we aim to improve current therapies for this devastating disease.

Citation Format: Christopher W. Schultz, Kevin O'Hayer, Teena Dhir, Oloruntoba Bolaji, Kathryn M. Bormes, Samantha Z. Brown, Henry Thomsett, Saswati Chand, Aditi Jain, Wei Jiang, Grace McCarthy, Charles J. Yeo, Austin Goetz, Avinoam Nevler, Jonathan R. Brody, Jordan M. Winter, Ranjan Preet, Dan Dixon, Jessica Bowers, Kelly Rhodes, Robert Getts. Gaps in the armor: Targeting HuR to sensitize pancreatic cancer [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 1961.