Oncogenic KIT or PDGFRA receptor tyrosine kinase mutations are compelling therapeutic targets in gastrointestinal stromal tumor (GIST), and treatment with the KIT/PDGFRA inhibitor imatinib is the standard of care for patients with advanced GIST. Polyclonal emergence of KIT/PDGFRA secondary mutations is the main mechanism of imatinib progression, making it challenging to overcome KIT/PDGFRA-inhibitor resistance. It is unclear whether there are other therapeutic targets in advanced GIST. Using genome-wide transcriptomic profiling of advanced versus early-stage GIST and CRISPR knockout functional screens, we demonstrate that CDK1 is frequently highly expressed in advanced GIST but not in early-stage GIST across three patient cohorts. High expression of CDK1 was associated with malignancy in GIST. CDK1 was critically required for advanced GIST, including imatinib-resistant GIST. CDK1 ablation led to robust proliferation inhibition. A mass spectrometry-based proteomics screen further revealed that AKT is a novel substrate of CDK1 kinase in GIST. CDK1 bound AKT and regulated its phosphorylation, thereby promoting GIST proliferation and progression. Importantly, a pharmacologic inhibitor of CDK1, RO-3306, disrupted GIST cell proliferation in CDK1 highly expressed GIST but not in CDK1-negative GIST cells and nontransformed fibroblast cells. Treatment with RO-3306 reduced tumor growth in both imatinib-resistant and imatinib-sensitive GIST xenograft mouse models. Our findings suggest that CDK1 represents a druggable therapeutic target in GIST and warrants further testing in clinical trials. Significance: These findings propose CDK1 as a novel cell-cycle–independent vulnerability in gastrointestinal stromal tumors, representing a new therapeutic opportunity for patients with advanced disease.
Central precocious puberty (CPP), largely caused by germline mutations in the MKRN3 gene, has been epidemiologically linked to cancers. MKRN3 is frequently mutated in non–small cell lung cancers (NSCLCs) with five cohorts. Genomic MKRN3 aberrations are significantly enriched in NSCLC samples harboring oncogenic KRAS mutations. Low MKRN3 expression levels correlate with poor patient survival. Reconstitution of MKRN3 in MKRN3-inactivated NSCLC cells directly abrogates in vitro and in vivo tumor growth and proliferation. MKRN3 knockout mice are susceptible to urethane-induced lung cancer, and lung cell–specific knockout of endogenous MKRN3 accelerates NSCLC tumorigenesis in vivo. A mass spectrometry–based proteomics screen identified PABPC1 as a major substrate for MKRN3. The tumor suppressor function of MKRN3 is dependent on its E3 ligase activity, and MKRN3 missense mutations identified in patients substantially compromise MKRN3-mediated PABPC1 ubiquitination. Furthermore, MKRN3 modulates cell proliferation through PABPC1 nonproteolytic ubiquitination and subsequently, PABPC1-mediated global protein synthesis. Our integrated approaches demonstrate that the CPP-associated gene MKRN3 is a tumor suppressor.
Pancreatic cancer is a highly aggressive malignancy with an overall 5‐year survival rate of <6% due to therapeutic resistance and late‐stage diagnosis. These statistics have not changed despite 50 years of research and therapeutic development. Pancreatic cancer is predicted to become the second leading cause of cancer mortality by the year 2030. Currently, the treatment options for pancreatic cancer are limited. This disease is usually diagnosed at a late stage, which prevents curative surgical resection. Chemotherapy is the most frequently used approach for pancreatic cancer treatment and has limited effects. In many other cancer types, targeted therapy and immunotherapy have made great progress and have been shown to be very promising prospects; these treatments also provide hope for pancreatic cancer. The need for research on targeted therapy and immunotherapy is pressing due to the poor prognosis of pancreatic cancer, and in recent years, there have been some breakthroughs for targeted therapy and immunotherapy in pancreatic cancer. This review summarizes the current preclinical and clinical studies of targeted therapy and immunotherapy for pancreatic cancer and ends by describing the challenges and outlook.
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