Citations

AbstractIt has been challenging to target mutant KRAS (mKRAS) in colorectal cancer (CRC) and other malignancies. Recent efforts have focused on developing inhibitors blocking molecules essential for KRAS activity. In this regard, SOS1 inhibition has arisen as an attractive approach for mKRAS CRC given its essential role as a guanine nucleotide exchange factor for this GTPase. Here, we demonstrated the translational value of SOS1 blockade in mKRAS CRC. We used CRC patient‐derived organoids (PDOs) as preclinical models to evaluate their sensitivity to SOS1 inhibitor BI3406. A combination of in silico analyses and wet lab techniques was utilized to define potential predictive markers for SOS1 sensitivity and potential mechanisms of resistance in CRC. RNA‐seq analysis of CRC PDOs revealed two groups of CRC PDOs with differential sensitivities to SOS1 inhibitor BI3406. The resistant group was enriched in gene sets involving cholesterol homeostasis, epithelial−mesenchymal transition, and TNF‐α/NFκB signaling. Expression analysis identified a significant correlation between SOS1 and SOS2 mRNA levels (Spearman's ρ 0.56, p < 0.001). SOS1/2 protein expression was universally present with heterogeneous patterns in CRC cells but only minimal to none in surrounding nonmalignant cells. Only SOS1 protein expression was associated with worse survival in patients with RAS/RAF mutant CRC (p = 0.04). We also found that SOS1/SOS2 protein expression ratio >1 by immunohistochemistry (p = 0.03) instead of KRAS mutation (p = 1) was a better predictive marker to BI3406 sensitivity of CRC PDOs, concordant with the significant positive correlation between SOS1/SOS2 protein expression ratio and SOS1 dependency. Finally, we showed that GTP‐bound RAS level underwent rebound even in BI3406‐sensitive PDOs with no change of KRAS downstream effector genes, thus suggesting upregulation of guanine nucleotide exchange factor as potential cellular adaptation mechanisms to SOS1 inhibition. Taken together, our results show that high SOS1/SOS2 protein expression ratio predicts sensitivity to SOS1 inhibition and support further clinical development of SOS1‐targeting agents in CRC.

Abstract Myocardial infarction is a leading cause of morbidity and mortality. While reperfusion is now standard therapy, pathological remodeling leading to heart failure remains a clinical problem. Cellular senescence has been shown to contribute to disease pathophysiology and treatment with the senolytic navitoclax attenuates inflammation, reduces adverse myocardial remodeling and results in improved functional recovery. However, it remains unclear which senescent cell populations contribute to these processes. To identify whether senescent cardiomyocytes contribute to disease pathophysiology post-myocardial infarction, we established a transgenic model in which p16 (CDKN2A) expression was specifically knocked-out in the cardiomyocyte population. Following myocardial infarction, mice lacking cardiomyocyte p16 expression demonstrated no difference in cardiomyocyte hypertrophy but exhibited improved cardiac function and significantly reduced scar size in comparison to control animals. This data demonstrates that senescent cardiomyocytes participate in pathological myocardial remodeling. Importantly, inhibition of cardiomyocyte senescence led to reduced senescence-associated inflammation and decreased senescence-associated markers within other myocardial lineages, consistent with the hypothesis that cardiomyocytes promote pathological remodeling by spreading senescence to other cell-types. Collectively this study presents a novel demonstration that senescent cardiomyocytes are major contributors to myocardial remodeling and dysfunction following a myocardial infarction. Therefore, to maximize the potential for clinical translation, it is important to further understand the mechanisms underlying cardiomyocyte senescence and how to optimize senolytic strategies to target this cell lineage.

Pathogenic variants in KMT5B , a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM # 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest ( n = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and Kmt5b haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in KMT5B -related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems.

AbstractCheckpoint inhibitor (CPI) therapy with anti–PD-1 antibodies has been associated with mixed outcomes in small cohorts of patients with relapsed aggressive B-cell lymphomas after CAR-T failure. To define CPI therapy efficacy more definitively in this population, we retrospectively evaluated clinical outcomes in a large cohort of 96 patients with aggressive B-cell lymphomas receiving CPI therapy after CAR-T failure across 15 US academic centers. Most patients (53%) had diffuse large B-cell lymphoma, were treated with axicabtagene ciloleucel (53%), relapsed early (≤180 days) after CAR-T (83%), and received pembrolizumab (49%) or nivolumab (43%). CPI therapy was associated with an overall response rate of 19% and a complete response rate of 10%. Median duration of response was 221 days. Median progression-free survival (PFS) and overall survival (OS) were 54 and 159 days, respectively. Outcomes to CPI therapy were significantly improved in patients with primary mediastinal B-cell lymphoma. PFS (128 vs 51 days) and OS (387 vs 131 days) were significantly longer in patients with late (&gt;180 days) vs early (≤180 days) relapse after CAR-T. Grade ≥3 adverse events occurred in 19% of patients treated with CPI. Most patients (83%) died, commonly because of progressive disease. Only 5% had durable responses to CPI therapy. In the largest cohort of patients with aggressive B-cell lymphoma treated with CPI therapy after CAR-T relapse, our results reveal poor outcomes, particularly among those relapsing early after CAR-T. In conclusion, CPI therapy is not an effective salvage strategy for most patients after CAR-T, where alternative approaches are needed to improve post–CAR-T outcomes.

Abstract Introduction: Clonal hematopoiesis (CH) is defined by acquisition of somatic mutations in hematopoietic stem cells with potential for expansion over time. CH is influenced by exposures to chemotherapy/radiation & has been associated with therapy related myeloid neoplasms (tMN). Peptide receptor radionuclide therapy (PRRT) is a radionuclide therapy and is FDA approved for neuroendocrine tumors (NET). PRRT has been associated with a 2-10% risk of tMN, especially with prior exposure to alkylating agents. A prior study of 13 NET patients found CH prevalence of 64%. We carried out a prospective assessment of CH in NET patients prior to PRRT. Methods: We evaluated pre-PRRT blood samples in 37 NET patients. Genomic DNA from mononuclear cells was analyzed for CH using a custom panel targeting 229 genes to a targeted depth of &gt;1000X. Results: After approval by Mayo Clinic IRB, 45 patients with Stage IV NET were enrolled & CH data was available for 37. Fifty-one percent of patients were female, with a median age of 68yrs (range, 34-84yrs). Types of NET included small bowel (51%), pancreatic (29%), carcinoid (8%), paraganglioma (5%), & other (5%). The median number of therapies prior to PRRT was 1 (range, 0-4) & included somatostatin analogues (SSA)-81%, alkylating agents-30%, & prior radiation-13%. Thirty-six of 37 patients had variants identified, 5 of which were presumed germline (DDX41, CDKN2B, CHEK2, POT1, ERBB2), & 17 (45.9%) had pathogenic variants meeting the operational definition of CH (DNMT3A, TET2, PPM1D, TP53, SF3B1, ASXL1). The median number of pathogenic variants per patient was 1 (range, 0-2), & 6 patients had &gt;1. In patients &gt;60yrs old, 46% had pathogenic variants & 3 patients with pathogenic variants (TET2, TP53, DNMT3A) were &lt;60 years old. The most common pathogenic variants were in epigenetic regulators, DNMT3A (37.5%) & TET2 (16.7%) with a median VAF of 2.8% (range, 0.70-50%). Eight patients (47%) with pathogenic CH had grade 1 cytopenias at baseline, compared to 10 patients (50%) without pathogenic CH. One patient had grade 3/4 cytopenia at baseline & had a missense variant in TP53 (VAF 50%) & history of exposure to anthracyclines, alkylating agents, platinum & radiation. The patient developed MDS before receiving PRRT. Pathogenic CH variants were more common in patients with previous exposure to radiation (p=0.008) or SSA (p=0.005). Two patients had PPM1D variants, both with a history of prior radiation, one with a history of prior alkylating treatment. Conclusion: To our knowledge this is the largest prospective evaluation of CH in NET. We identified CH to be present in 46% of patients & DNMT3A mutations were most common. This establishes the clonal landscape with mutations involving epigenetic regulators, DNA damage repair, transcription & splicing factors. Prospective longitudinal evaluation will evaluate the association between CH, cytopenias and tMN. Citation Format: Yael Kusne, Terra Lasho, Zaid Elsabbagh, Abhishek Mangaonkar, Rachel Eiring, Timothy Hobday, Jason Starr, Tanios Bekaii-Saab, Thorvardur Halfdanarson, Mrinal Patnaik, Mohamad Sonbol. Prevalence of clonal hematopoiesis in neuroendocrine tumor patients prior to lutetium 177 dotatate therapy (Lu177): A prospective trial of 36 patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5928.

Abstract There are no routine screening tests for head and neck (H&N) cancers, which account for approximately 4% of all cancers in the US. Risk factors for oropharyngeal cancer include smoking and human papillomavirus (HPV) infection. An MCED test that uses a cell-free DNA-based targeted methylation assay and machine learning classifiers to detect a shared cancer signal and predict the cancer signal origin (CSO) is available as a complement to existing single-cancer screening tests. If a cancer signal is detected, the positive result is reported with 1 or 2 CSO prediction(s). We report here a tonsil cancer case detected using an MCED test and review the CSO-guided diagnostic journey. An asymptomatic 74-year-old White male (BMI: 29.9 kg/m2) with history of chronic lymphocytic leukemia (CLL; Rai stage 0; 13q, CD38, and ZAP-70 negative; no treatment was needed) 17 years prior and papillary thyroid cancer (stage IVa; pT3N1bM0; thyroidectomy and radiation therapy; no recurrence) 8 years prior was screened using the MCED test. Patient had an elevated PSA level (9-10 ng/mL) and was a nonsmoker. Fifteen days after a blood sample was collected for analysis, a positive test result (CSO prediction=H&N) was communicated to the patient (Day 1). PET showed abnormal uptake in the right tonsil (Day 28). The patient was referred for an ENT consult and underwent a right lymph node biopsy (Day 54). The biopsy showed invasive moderately differentiated SCC, non-keratinizing, forming a 3 × 2.1 × 1.2 cm mass (Day 57). Patient underwent right tonsillectomy (the surgical margins were negative for invasive or in situ carcinoma) and lymph node dissection (Day 57). The cancer was diagnosed as HPV-mediated p16+, pT2, pN1, cM0 (stage I) SCC of the oropharynx (Day 57). No chemotherapy or radiation was required due to the early stage of detection. The patient will follow-up with ENT and radiation oncology. The MCED test detected a cancer signal and predicted an accurate CSO for an asymptomatic individual with stage I HPV-mediated oropharyngeal SCC. Notably, despite a history of CLL and an elevated PSA level, the test accurately predicted CSO leading to a directed workup diagnosing asymptomatic cancer in less than 2 months, while the cancer was still at stage I. In the case-control Circulating Cell-free Genome Atlas study, the MCED test sensitivity to detect a cancer signal was 63% in stage I H&N cancer. The use of this MCED test led to detection of cancer in a patient with CLL history and treatment (surgery without complications and without chemotherapy or radiation) with curative intent. Citation Format: Janet Vittone, Julia Feygin, Jason Carey. A case of stage I HPV-mediated oropharyngeal squamous cell carcinoma (SCC) diagnosed using a multi-cancer early detection (MCED) test [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6523.

Abstract Cancer cachexia is a multifactorial syndrome entailing muscle and fat wasting, inflammation, and metabolic dysfunction. Pancreatic cancer has the highest incidence of cachexia at around 80%. However, there are no FDA approved therapy for cachexia in the clinic yet. This is mostly because of the failure of preclinical therapies to demonstrate success in the clinic. Most preclinical studies utilize 6-8 week old mice which roughly corresponds to a human age of ~ 20 years. However, the median age of diagnosis of pancreatic cancer is ~70 years. Given widespread physiology, microenvironment, and metabolism differences in young and aged skeletal muscle, we sought to study cancer cachexia in mice aged to &gt;78 weeks, which corresponds to a human age of greater than 60 years. Our previously published study reported little difference in tumor growth or survival between the two cohorts, yet significant alterations in the muscle transcriptome. Building on this work, we show significant differences in the muscle metabolome of young/aged control and tumor bearing mice. Notably, histamine was higher in aged versus young control mice and even higher in the aged tumor-bearing cohort. We show higher activity of histamine decarboxylase (HDC), the enzyme that converts histidine to histamine in the muscles of aged tumor-bearing mice. Addition of cancer conditioned-media (CM) to C2C12 myotubes was able to induce histamine production and HDC activity in vitro, which demonstrates the ability of muscle cells to induce histamine independent of mast cells. We further show that addition of histamine to myotubes is sufficient to increase atrophy-associated markers. Inhibition of HDC activity by α-fluoromethylhistidine (FMH) in the in vitro model of cachexia protected against myotube thinning. Finally, we treated tumor-bearing aged mice with FMH and observed a) decreased histamine in the muscles 2) decreased HDC activity in the muscles 3) decreased muscle wasting, 4) decreased atrophy markers. Together, we present a novel wasting-associated metabolic pathway and corresponding therapeutic avenue for cancer cachexia that may have been overlooked if not for the use of a more-age-appropriate model of pancreatic cancer. Citation Format: Aneesha Dasgupta, Rebecca E. Schmitt, Jessica Z. Schneider, Tatsuyoshi Kono, Chih-Chun Lee, Carmella Evans-Molina, Jason D. Doles. Targeting differential metabolism in an aged model of cancer cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 356.

Abstract Chemotherapy-induced cognitive impairment (CICI, also termed “chemobrain”) is a major neurotoxic side effect exhibited by a wide range of chemotherapeutic agents. These side effects affect approximately 14 million cancer survivors. More importantly, CICI persists well after cessation of therapy, severely interfering with quality of life. Unfortunately, there is no treatment and novel therapies are urgently needed. Utilizing cisplatin, a platinum-based chemotherapy, to model chemobrain mice in vivo, we have established that cisplatin accelerates the brain aging process thus leading to long-term memory impairment in mice similar to what is clinically reported. We further show that cisplatin causes oxidative DNA damage, mitochondrial defects, impaired neurogenesis, synaptic defects, and increased gliosis in the adult hippocampus, a brain region critical for learning and memory. Mechanistically, our RNA-sequencing and qRT-PCR analysis revealed that cisplatin dramatically increases COX-2 (Ptgs2) expression and its major product, prostaglandin E2 (PGE2) in adult mouse brain and human cortical neurons derived from induced pluripotent stem cells (iPSCs). Similar as cisplatin treatment, the levels of COX-2 expression began to increase at 0.1 µM methotrexate treatment, which significantly increased at 1 µM in human cortical neurons, indicating that COX-2 induction is a common pathogenic mechanism mediating cognitive impairment associated with cisplatin and methotrexate in spite of the fact that these compounds have different mechanisms of action for cancer eradication. Most importantly, NS-398, a selective COX-2 inhibitor, effectively prevents cognitive deficits in mice and reduction in cell viability of human neurons associated with these chemotherapies, without promoting tumor growth or interfering with cisplatin’s anti-tumor activity. Taken together, our findings strongly suggest that COX-2 induction is a main cause of CICI, making COX-2 inhibition a therapeutic target for CICI. Given that COX-2 inhibitors are currently being tested in cancer prevention as well as age-related memory loss in clinical trials, inhibiting COX-2 may have far-reaching therapeutic effects on CICI and cancer treatment, which can be applied quickly, safely, and effectively to clinical trials, in the effort to improve cancer survivor quality of life. Citation Format: Mohammad Abdur Rashid, Jason J. Tang, Ki-Hyun Yoo, Ana Corujo-Ramirez, Sang Hoon Kim, Alfredo Oliveros, Peter Cole, John R. Hawse, Mi-Hyeon Jang. Blockade of the cyclooxygenase-2 prevents chemotherapy-induced cognitive impairments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2694.