👤 Katsuhiro Masago

Pancreatic ductal adenocarcinomas (PDACs) with wild-type KRAS constitute a small fraction of PDACs, and these tumors were recently shown to harbor frequent actionable oncogenic mutations and fusions. However, the clinicopathological features of KRAS wild-type PDAC have not been well studied. Additionally, precancerous lesions occurring in patients with KRAS wild-type PDACs have rarely been characterized. Here, we investigated the clinicopathological characteristics and outcomes of 75 patients with KRAS wild-type PDAC. Molecular analyses were performed in 40 patients using targeted DNA and whole-exome sequencing and targeted RNA sequencing. We demonstrated that patients with metastatic PDAC with wild-type KRAS were younger (median 59.5 years) than those with mutated KRAS (median 67 years, p < 0.000055). The wild-type KRAS status was not a significant prognostic factor for metastatic disease. Molecularly, genes in the RAS pathway are frequently mutated or rearranged (46%, 16/35), including mutations in BRAF, NRAS, HRAS, EGFR, MAP2K1, FGFR1, FGFR3 and ERBB4 and fusions of FGFR2 (FGFR2::CCDC147, FGFR2::CAT, FGFR2::TXLNA), ALK (STRN::ALK, EML4::ALK), and BRAF (TRIP11::BRAF). Mismatch repair deficiency was identified in 10% (4/39) of patients. Potentially actionable alterations were identified frequently in KRAS wild-type PDACs (30%, 12/40), in which nontubular-type carcinomas were significantly enriched with actionable alterations compared with tubular adenocarcinomas [67% (6/9) versus 16% (5/31); p = 0.007]. Finally, we investigated the precursors of PDACs in 13 pancreatectomy specimens from patients with KRAS wild-type PDAC. We identified three pancreatic intraepithelial neoplasias (PanINs) and two intraductal papillary mucinous neoplasms (IPMNs) harboring oncogenic fusions of ALK and BRAF and driver mutations in BRAF and AKT1. This study suggests that in the context of unmutated KRAS, PDAC is driven by alternative oncogenic mutations or fusions of RAS pathway genes, which may be introduced during the early phase of tumorigenesis. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. Show less

Melanocortin 4 receptor-deficient (MC4R-KO) mice fed a high-fat diet (HFD) develop liver pathology similar to human nonalcoholic steatohepatitis (NASH). However, although liver histology and blood biochemistry have been reported, hepatic function has not been evaluated. In the present study, we evaluated hepatic function in MC4R-KO mice fed an HFD using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with gadolinium‑ethoxybenzyl‑diethylenetriamine pentaacetic acid (Gd-EOB-DTPA). Wild type (WT) mice and MC4R-KO mice were fed a standard diet (SD) or an HFD for 20 weeks. The hepatic signal intensity was obtained from DCE-MRI images, and relative enhancement (RE), the time to maximum RE (T Histological analysis with nonalcoholic fatty liver disease activity score (NAS) revealed that MC4R-KO mice fed an HFD achieved the NAS of 5. There was moderate fibrosis in MC4R-KO mice fed an HFD. DCE-MRI with Gd-EOB-DTPA showed that T MC4R-KO mice fed an HFD developed obesity and NASH. The liver kinetics of Gd-EOB-DTPA were significantly different in MC4R-KO mice fed an HFD from WT mice, and correlated with the histopathologic score. These results suggest that MC4R-KO mice fed an HFD mimic the hepatic pathology and liver function of human NASH, and therefore might be useful for the study of hepatic dysfunction during the fibrotic stage of NASH. Show less