Search

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer that has remained clinically challenging to manage. Here we employ an RNAi-based in vivo functional genomics platform to determine epigenetic vulnerabilities across a panel of patient-derived PDAC models. Through this, we identify protein arginine methyltransferase 1 (PRMT1) as a critical dependency required for PDAC maintenance. Genetic and pharmacological studies validate the role of PRMT1 in maintaining PDAC growth. Mechanistically, using proteomic and transcriptomic analyses, we demonstrate that global inhibition of asymmetric arginine methylation impairs RNA metabolism, which includes RNA splicing, alternative polyadenylation, and transcription termination. This triggers a robust downregulation of multiple pathways involved in the DNA damage response, thereby promoting genomic instability and inhibiting tumor growth. Taken together, our data support PRMT1 as a compelling target in PDAC and informs a mechanism-based translational strategy for future therapeutic development.Statement of significancePDAC is a highly lethal cancer with limited therapeutic options. This study identified and characterized PRMT1-dependent regulation of RNA metabolism and coordination of key cellular processes required for PDAC tumor growth, defining a mechanism-based translational hypothesis for PRMT1 inhibitors.

Dickkopf1 (DKK1) is a secretory protein that antagonizes oncogenic Wnt signaling by binding to the Wnt coreceptor lowdensity lipoprotein receptor-related protein 6 (LRP6). DKK1 may also regulate its own signaling to promote cancer cell proliferation, but the mechanism is not understood. Here, we identified cytoskeleton-associated protein 4 (CKAP4) as a DKK1 receptor and evaluated CKAP4-mediated DKK1 signaling in cancer cell proliferation. We determined that DKK1 binds CKAP4 and LRP6 with similar affinity but interacts with these 2 receptors with different cysteine-rich domains. DKK1 induced internalization of CKAP4 in a clathrin-dependent manner, further supporting CKAP4 as a receptor for DKK1. DKK1/CKAP4 signaling activated AKT by forming a complex between the proline-rich domain of CKAP4 and the Src homology 3 domain of PI3K, resulting in proliferation of normal cells and cancer cells. Expression of DKK1 and CKAP4 was frequent in tumor lesions of human pancreatic and lung cancers, and simultaneous expression of both proteins in patient tumors was negatively correlated with prognosis and relapse-free survival. An anti-CKAP4 antibody blocked the binding of DKK1 to CKAP4, suppressed AKT activity in a human cancer cell line, and attenuated xenograft tumor formation in immunodeficient mice. Together, our results suggest that CKAP4 is a potential therapeutic target for cancers that express both DKK1 and CKAP4., Introduction Dickkopf1 (DKK1) was originally identified as an embryonic head inducer in Xenopus embryos and shown to be a secreted protein that antagonizes Wnt signaling (1, 2). Of the multiple [...]

Dickkopf1 (DKK1) is a secretory protein that antagonizes oncogenic Wnt signaling by binding to the Wnt coreceptor low-density lipoprotein receptor-related protein 6 (LRP6). DKK1 may also regulate its own signaling to promote cancer cell proliferation, but the mechanism is not understood. Here, we identified cytoskeleton-associated protein 4 (CKAP4) as a DKK1 receptor and evaluated CKAP4-mediated DKK1 signaling in cancer cell proliferation. We determined that DKK1 binds CKAP4 and LRP6 with similar affinity but interacts with these 2 receptors with different cysteine-rich domains. DKK1 induced internalization of CKAP4 in a clathrin-dependent manner, further supporting CKAP4 as a receptor for DKK1. DKK1/CKAP4 signaling activated AKT by forming a complex between the proline-rich domain of CKAP4 and the Src homology 3 domain of PI3K, resulting in proliferation of normal cells and cancer cells. Expression of DKK1 and CKAP4 was frequent in tumor lesions of human pancreatic and lung cancers, and simultaneous expression of both proteins in patient tumors was negatively correlated with prognosis and relapse-free survival. An anti-CKAP4 antibody blocked the binding of DKK1 to CKAP4, suppressed AKT activity in a human cancer cell line, and attenuated xenograft tumor formation in immunodeficient mice. Together, our results suggest that CKAP4 is a potential therapeutic target for cancers that express both DKK1 and CKAP4. [ABSTRACT FROM AUTHOR]

The therapeutic benefit of recently developed mutant KRAS (mKRAS) inhibitors has been limited by the rapid onset of resistance. Here, we aimed to delineate the mechanisms underlying acquired resistance to mKRAS inhibition and identify actionable targets for overcoming this clinical challenge. Previously, we identified Syndecan-1 (SDC1) as a key effector for pancreatic cancer progression whose surface expression is driven by mKRAS. By leveraging both pancreatic and colorectal cancer models, we found that surface SDC1 expression was initially diminished upon mKRAS inhibition, but recovered in tumor cells that bypass mKRAS dependency. Functional studies showed that these tumors depended on SDC1 for survival, further establishing SDC1 as a driver for the acquired resistance to mKRAS inhibition. Mechanistically, we revealed that the YAP1-SDC1 axis was the major driving force for bypassing mKRAS dependency to sustain nutrient salvage machinery and tumor maintenance. Specifically, YAP1 activation mediated the recovery of SDC1 localization on cell surface that sustained macropinocytosis and enhanced the activation of multiple RTKs, promoting resistance to KRAS-targeted therapy. Overall, our study has provided the rationale for targeting the YAP-SDC1 axis to overcome resistance to mKRAS inhibition, thereby revealing new therapeutic opportunities for improving the clinical outcome of patients with KRAS-mutated cancers.

A 51-year-old woman presented to our hospital complaining of a lower abdominal mass and dysuria. She was diagnosed with advanced sigmoid colon cancer. The tumor was large, involving the bladder, and occupying the pelvic cavity. She received neoadjuvant chemotherapy with 4 courses of mFOLFOX6, in addition to panitumumab. The treatment resulted in a marked reduction of the tumor. A laparoscopic sigmoid colon resection, total cystectomy, neobladder reconstruction, complete uterine and bilateral adnexa resection and partial ileal resection were performed. The histopathological diagnosis was ypT4b(bladder), ypN0, ypStage Ⅱc, all with negative surgical margins. Adjuvant chemotherapy was not administered owing to the patient's refusal. She remained recurrence-free for 3 years of postoperative follow up.

A 76-year-old man came to our hospital for a close examination after an abnormal finding during a medical checkup. Upper gastrointestinal endoscopy revealed a circumferential flat lesion with irregularity in the second to third portions of the duodenum. Biopsy diagnosed papillary adenocarcinoma. Contrast-enhanced CT of the abdomen showed no evidence of lymph node enlargement and distant metastasis. Endoscopic depth of the lesion was estimated to be intramucosal carcinoma, but it was approximately 60 mm in size, circumferential, and located near the papilla Vater. Therefore, endoscopic resection was deemed difficult. Subtotal stomach-preserving pancreaticoduodenectomy was performed. Postoperative pathological examination revealed type 0-Ⅱa, tub1>pap, pTis, Ly0, V0, 80×50 mm, BD1, Ex0, Pn0, pPM0, pDM0, pN0, pStage 0. There has been no recurrence since then. Lateral spreading duodenal carcinoma is a rare disease, and endoscopic resection, local resection, and pancreaticoduodenectomy have been reported as treatment options. We report a case of resection of a large lateral spreading duodenal carcinoma with a review of the literature.

A 74-year-old man was under follow-up after esophageal cancer surgery and CRT for hypopharyngeal cancer. Follow-up endoscopy revealed an ulcerative lesion in the lower gastric tube, and biopsy showed group 5(tub1). Endoscopic resection was difficult, and surgery was decided. Gastric tube resection and subcutaneous jejunum reconstruction were performed. Postoperatively, chylothorax was observed. Enteral nutrition was discontinued, and the patient was managed with TPN, and continuous subcutaneous octreotide and continuous intravenous etyrefrine were started. Even after conservative treatment was started, the pleural effusion of about 2,000 mL/day was observed from the right thoracic drain. On postoperative day 14, lymphangiography was performed with lipiodol from the left inguinal lymph node. The pleural fluid was temporarily decreased to less than 500 mL/day, but it began to drain again at a rate of 1,000 mL/day. On postoperative day 30, the patient developed fever and elevated inflammatory findings due to pneumonia and empyema, and drain drainage gradually decreased. The drain was removed on postoperative day 41. The patient was discharged home on postoperative day 72.