Acid Ceramidase (ASAH1) Mediates Intrinsic and Intercellular Transfer of Proteasome Inhibitor Resistance in Multiple Myeloma

INTRODUCTION: Despite proteasome inhibitors (PIs) improving multiple MM (MM) outcomes, patients often become resistant. Identifying mechanisms of resistance with translational potential are an urgent unmet clinical need. Preliminary studies from our group have identified that the therapeutically targetable acid ceramidase, ASAH1, is a key mediator of PI resistance and its presence in extracellular vesicles (EVs) derived from resistant MM cells, confers PI resistance on drug naïve MM cells. METHODS: Nanosight technology, transmission electron microscopy and immunoblot were used to define EVs. Viability and apoptosis assays were used to determine the effects of EVs and inhibitors on resistance acquisition/sensitization to PIs. LC-MS was used to interrogate EV cargo contents. Clinical relevance of ASAH1 was determined in multiple human data cohorts (M2GEN and MMRF CoMMpass). Genetic (shRNA) and pharmacological (ceranib-2) approaches were used to assess the role of ASAH1 mechanistically in vitro and in vivo using multiple isogenic naïve and PI resistant cell lines, patient derived CD138+ MM cells and NSG mouse models. RESULTS: Co-culture of sensitive MM cells with resistant MM-EVs alone significantly protected against PI cytotoxicity. Proteomic profiling revealed high levels of ASAH1 in EVs derived from PI resistant MM cells. Further, we observed ASAH1 is abundant in lysates of multiple PI resistant cell lines compared to their isogenic drug sensitive counterparts. In human datasets, high ASAH1 expression was noted in PI resistant MM patients compared to those newly diagnosed and correlated with significantly shorter survival times. Mechanistically, knockdown of ASAH1 led to reduced conversion of ceramide to sphingosine 1-phosphate (S1-P) and decreased expression/activity of the anti-apoptotic proteins MCL-1, BCL2 and BCL-xL and increases in pro-apoptotic BIM and NOXA. Notably, ASAH1 knockdown also significantly sensitized the cells to PI treatment and this effect was rescued by addition of exogenous S1-P. Pharmacological inhibition of ASAH1 with ceranib-2 also sensitized resistant cells to PI treatment and prevented EV mediated resistance transfer in vitro. This was recapitulated ex vivo with human clinical samples. Our orthotopic in vivo model using PI-resistant U266-PSR cells show that ceranib-2 is highly effective in limiting the growth of PI-resistant disease, protecting against MM induced bone disease, and increasing overall survival compared to both bortezomib and vehicle controls. CONCLUSION: We define the ceramidase ASAH1 as a novel, druggable target for the treatment of PI resistant MM. Disclosures Hampton: M2Gen: Current Employment. Siqueira Silva: AbbVie Inc.: Research Funding; Karyopharm Therapeutics Inc.: Research Funding. Shain: Janssen oncology: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi Genzyme: Consultancy, Speakers Bureau; Karyopharm Therapeutics Inc.: Honoraria, Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; GlaxoSmithLine, LLC: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Adaptive Biotechnologies Corporation: Consultancy, Speakers Bureau; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding.

DDRE-06. TARGETING THE SPHINGOLIPID BALANCE VIA ACID CERAMIDASE INHIBITION TO DECREASE GROWTH OF TMZ-RESISTANT GLIOBLASTOMA AND BLOCK MIGRATION

Dysregulated sphingolipid metabolism is associated with many cancers; allowing cells to evade apoptosis through increases in sphingosine-1-phosphate (S1P) and decreases in ceramides. Ceramides can be hydrolyzed by ceramidases to sphingosine, which can then be phosphorylated by sphingosine kinases to S1P. S1P allows cells to evade apoptosis and increase migration, while shifts toward ceramides favor cell death. Glioblastoma (GBM) exhibits shifts in the sphingolipid balance towards S1P, contributing to chemoresistance and migration. Understanding of sphingolipid metabolism in GBM is still limited, and currently, there are no approved treatments to target the dysregulation. Acid ceramidase (ASAH1), a key enzyme in the production of S1P, is highly expressed in GBM and is associated with worse survival of GBM patients, as per The Cancer Genome Atlas data. To address the altered sphingolipid metabolism and therapeutic resistance in GBM, we explored the efficacy of pharmacologic and genetic inhibition of ASAH1 in both parental and temozolomide (TMZ)-resistant patient-derived xenografts. Cells were infected with ASAH1 shRNA or treated with ASAH1 inhibitors and assessed for cell growth and migration. Our work suggests that pharmacologic inhibition of ASAH1 induces cell death and that this effect is maintained in TMZ-resistant cells. Furthermore, we find a novel role for carmofur, an ASAH1 inhibitor, in the inhibition of GBM migration. Together, these data suggest the potential utility of normalizing the sphingolipid balance in the context of GBM TMZ resistance.

Alterations of lipid metabolism provide serologic biomarkers for the detection of asymptomatic versus symptomatic COVID-19 patients

COVID-19 pandemic exerts a health care emergency around the world. The illness severity is heterogeneous. It is mostly unknown why some individuals who are positive for SARS-CoV-2 antibodies stay asymptomatic while others show moderate to severe disease symptoms. Reliable biomarkers for early detection of the disease are urgently needed to attenuate the virus’s spread and help make early treatment decisions. Bioactive sphingolipids play a crucial role in the regulation of viral infections and pro-inflammatory responses involved in the severity of COVID-19. However, any roles of sphingolipids in COVID-19 development or detection remain unknown. In this study, lipidomics measurement of serum sphingolipids demonstrated that reduced sphingosine levels are highly associated with the development of symptomatic COVID-19 in the majority (99.24%) SARS-CoV-2-infected patients compared to asymptomatic counterparts. The majority of asymptomatic individuals (73%) exhibited increased acid ceramidase (AC) in their serum, measured by Western blotting, consistent with elevated sphingosine levels compared to SARS-CoV-2 antibody negative controls. AC protein was also reduced in almost all of the symptomatic patients’ serum, linked to reduced sphingosine levels, measured in longitudinal acute or convalescent COVID-19 samples. Thus, reduced sphingosine levels provide a sensitive and selective serologic biomarker for the early identification of asymptomatic versus symptomatic COVID-19 patients.

O13 Acid ceramidase: a potential biomarker for locally advanced rectal cancer?

Introduction We have previously utilized proteomic and immuno-histochemical data to validate that high levels of acid ceramidase (AC) expression confers poorer neoadjuvant response in rectal cancer. Biological (siRNA, plasmid and CRISPR) AC manipulation altered radiosensitivity in-vitro. We aimed to assess the radiosensitising effect of pharmacological AC inhibitions and elucidate the potential underlying mechanism. Methods Optimal drug dosing was achieved using ELISA activity assays in multiple colorectal cancer cell lines (HCT116, HT29, LIM1215). Carmofur and a novel small molecular inhibitor (LCL521) were used as pharmacological inhibitors. Standard clonogenic assays assessed cell survival following increasing irradiation (2 D), volume change in 3 D spheroids and cell viability in patient derived organoids. Annexin V/PI staining was used to determine apoptosis. Results Carmofur clonogenic assays demonstrated reduced colony formation efficiency (CFE) and improved radiosensitivity across cell lines. HCT116 showed 0.438(CFE) control v 0.183(CFE) carmofur at 1 Gy, 0.140(CFE) control v 0.076(CFE) at 2 Gy (P = 0.000563). LCL521 dosing improved radiosensitivity in spheroid models. HCT116 volume day-15 2.36x10-5mm v control 4.15x10-5mm. siRNA-AC demonstrated increased apoptosis across time points compared to NT control (P = 0.035), and increased poly-ADP ribose polymerase-1 (PARP-1) cleavage in a p53-dependent process. Conclusion Initial work demonstrates that pharmacological inhibition of AC produces comparative radiosensitizing effects in these cell lines and cancer models. siRNA-AC increases apoptosis, suggestive of a potential underlying mechanism. This work further solidifies AC as a potential biomarker, however further recapitulation in more complex models and ultimately in-vivo is required to establish a translatable clinical role.