Pancreatic ductal adenocarcinomas (PDAC) depend on autophagy for survival; however, the metabolic substrates that autophagy provides to drive PDAC progression are unclear. Ferritin, the cellular iron ...storage complex, is targeted for lysosomal degradation (ferritinophagy) by the selective autophagy adaptor NCOA4, resulting in release of iron for cellular utilization. Using patient-derived and murine models of PDAC, we demonstrate that ferritinophagy is upregulated in PDAC to sustain iron availability, thereby promoting tumor progression. Quantitative proteomics reveals that ferritinophagy fuels iron-sulfur cluster protein synthesis to support mitochondrial homeostasis. Targeting NCOA4 leads to tumor growth delay and prolonged survival but with the development of compensatory iron acquisition pathways. Finally, enhanced ferritinophagy accelerates PDAC tumorigenesis, and an elevated ferritinophagy expression signature predicts for poor prognosis in patients with PDAC. Together, our data reveal that the maintenance of iron homeostasis is a critical function of PDAC autophagy, and we define NCOA4-mediated ferritinophagy as a therapeutic target in PDAC.
Autophagy and iron metabolism are metabolic dependencies in PDAC. However, targeted therapies for these pathways are lacking. We identify NCOA4-mediated selective autophagy of ferritin ("ferritinophagy") as upregulated in PDAC. Ferritinophagy supports PDAC iron metabolism and thereby tumor progression and represents a new therapeutic target in PDAC. See related commentary by Jain and Amaravadi, p. 2023. See related article by Ravichandran et al., p. 2198. This article is highlighted in the In This Issue feature, p. 2007.
The mechanisms underlying metabolic adaptation of pancreatic ductal adenocarcinoma (PDA) cells to pharmacologic inhibition of RAS-MAPK signaling are largely unknown. Using transcriptome and chromatin ...immunoprecipitation profiling of PDA cells treated with the MEK inhibitor (MEKi) trametinib, we identify transcriptional antagonism between c-MYC and the master transcription factors for lysosome gene expression, the MiT/TFE proteins. Under baseline conditions, c-MYC and MiT/TFE factors compete for binding to lysosome gene promoters to fine-tune gene expression. Treatment of PDA cells or patient organoids with MEKi leads to c-MYC downregulation and increased MiT/TFE-dependent lysosome biogenesis. Quantitative proteomics of immunopurified lysosomes uncovered reliance on ferritinophagy, the selective degradation of the iron storage complex ferritin, in MEKi-treated cells. Ferritinophagy promotes mitochondrial iron-sulfur cluster protein synthesis and enhanced mitochondrial respiration. Accordingly, suppressing iron utilization sensitizes PDA cells to MEKi, highlighting a critical and targetable reliance on lysosome-dependent iron supply during adaptation to KRAS-MAPK inhibition.
Reduced c-MYC levels following MAPK pathway suppression facilitate the upregulation of autophagy and lysosome biogenesis. Increased autophagy-lysosome activity is required for increased ferritinophagy-mediated iron supply, which supports mitochondrial respiration under therapy stress. Disruption of ferritinophagy synergizes with KRAS-MAPK inhibition and blocks PDA growth, thus highlighting a key targetable metabolic dependency. See related commentary by Jain and Amaravadi, p. 2023. See related article by Santana-Codina et al., p. 2180. This article is highlighted in the In This Issue feature, p. 2007.
What happens when kidney stone clearance is not feasible? We report the case of a 46-year-old male who presented for review with bilateral congenital non-obstructive calyceal dilatation ...(megacalycosis) and high volume bilateral renal calculi in the setting of stage four chronic kidney disease. Since complete stone clearance was deemed futile, thus a consensus was made between Urology and Nephrology, and treatment goals were focused on addressing symptoms, preserving renal function and preventing urinary tract infections until renal transplantation is needed. This case highlights that for some patients with severe complex kidney stone disease, an alternative management plan is needed.
BackgroundAberrant translation of the non-coding genome in cancer can generate novel peptides capable of presentation by major histocompatibility complex class I (MHC-I; HLA-I in humans) and these ...non-canonical peptide sources can broaden the landscape of potentially targetable antigens in low-to-intermediate mutational burden malignancies. While emerging evidence suggests that translation of unannotated open reading frames (uORFs) can give rise to MHC class I-associated peptides (MAPs) across a range of malignancies, it is currently unknown to what extent these translation products are truly cancer-restricted and how effectively the resulting non-canonical MAPs (ncMAPs) can elicit a T cell response.MethodsWe leveraged twelve pancreatic cancer (PDAC) patient-derived organoids (PDOs) to purify the malignant compartment from low tumor cellularity tumor specimens. We developed a cutting-edge proteogenomics pipeline, coupled with high-depth immunopeptidomics to identify pancreatic cancer MAPs derived from somatic mutations, retained introns, and uORFs. To investigate the cancer-specificity of ncMAPs, we developed a translation-centric analysis pipeline that examines translation of uORFs encoding ncMAPs across a range of healthy tissues, including healthy thymus. To evaluate for immunogenicity, we employed a highly sensitive ex vivo platform to prime and expand ncMAP-specific cytotoxic T lymphocytes (CTLs) and evaluate cytolytic potential.ResultsWe demonstrate that ncMAPs are abundant and predominate over mutation-derived peptides in the pancreatic cancer immunopeptidome, establishing a novel class of recurrent cancer-restricted epitopes available for immune recognition. We observed widespread translation and MHC-I presentation of numerous ncMAPs across many healthy tissues, highlighting the importance of our translation-centric approach to assess cancer-restriction. Excitingly, we nominated over 500 ncMAPs that exhibit cancer-specific translation patterns. Approximately 30% of ncMAPs exhibited bona fide cancer-restricted translation patterns, and a substantial subset of these were shared among patients. We next interrogated immunogenicity using a highly sensitive ex vivo vaccination platform and demonstrated that the majority of cancer-restricted ncMAPs evaluated were highly immunogenic. Remarkably, the proportion of ncMAPs harboring immunogenic potential was substantially higher than mutation-derived neoepitopes and tumor-associated antigens, underscoring their therapeutic potential relative to traditional immunotherapy targets.ConclusionsThese findings demonstrate that aberrant translation in pancreatic cancer can give rise to recurrent cancer-restricted ncMAPs capable of recognition by cytotoxic T lymphocytes. Collectively, our findings furnish a novel set of recurrent, cancer-restricted immunotherapy targets not subject to central tolerance. We believe these findings will prompt translation-centric investigations in other solid tumors. We envision that these novel antigens will augment ongoing efforts to treat pancreatic cancer patients with vaccines and cell-based therapies.Ethics ApprovalInformed consent was obtained from patients at least 18 years old with pancreatic cancer under Dana-Farber/Harvard Cancer Center Institutional Review Board (IRB)-approved protocols 11–104, 17–000, 03–189, and/or 14–408 for tissue collection, molecular analysis, and organoid generation.
Broad-spectrum RAS inhibition has the potential to benefit roughly a quarter of human patients with cancer whose tumours are driven by RAS mutations
. RMC-7977 is a highly selective inhibitor of the ...active GTP-bound forms of KRAS, HRAS and NRAS, with affinity for both mutant and wild-type variants
. More than 90% of cases of human pancreatic ductal adenocarcinoma (PDAC) are driven by activating mutations in KRAS
. Here we assessed the therapeutic potential of RMC-7977 in a comprehensive range of PDAC models. We observed broad and pronounced anti-tumour activity across models following direct RAS inhibition at exposures that were well-tolerated in vivo. Pharmacological analyses revealed divergent responses to RMC-7977 in tumour versus normal tissues. Treated tumours exhibited waves of apoptosis along with sustained proliferative arrest, whereas normal tissues underwent only transient decreases in proliferation, with no evidence of apoptosis. In the autochthonous KPC mouse model, RMC-7977 treatment resulted in a profound extension of survival followed by on-treatment relapse. Analysis of relapsed tumours identified Myc copy number gain as a prevalent candidate resistance mechanism, which could be overcome by combinatorial TEAD inhibition in vitro. Together, these data establish a strong preclinical rationale for the use of broad-spectrum RAS-GTP inhibition in the setting of PDAC and identify a promising candidate combination therapeutic regimen to overcome monotherapy resistance.
