Foo, W. C. | Search bioRxiv

bioRxiv2026

KRAS inhibition is an effective therapy for appendiceal adenocarcinoma

BackgroundAppendiceal adenocarcinoma (AA) is a rare cancer with limited treatment options. KRAS is the most commonly mutated gene in AA and a promising therapeutic target, but its preclinical and translational relevance in AA remains unclear. MethodsWe evaluated KRASG12D-specific (MRTX1133) and pan-KRAS inhibitor (RMC-6236) in KRASmut organoid and orthotopic PDX models of AA. Tumor-intrinsic and microenvironmental responses were characterized using multi-omics profiling. Clinical outcomes were also assessed in six heavily pre-treated AA patients treated with KRAS inhibitors. ResultsMRTX1133 was highly effective for KRASG12D organoids (IC50=4.1 nM); both KRASG12D and KRASG12V organoids were sensitive to RMC-6236 (IC50=4.4 nM vs 0.5 nM, respectively). In orthotopic PDX models of peritoneal carcinomatosis from AA, MRTX1133 significantly reduced tumor growth in the KRASG12D model TM00351, and RMC-6236 reduced tumor growth in KRASG12V model AAPDX-16. Pathologic evaluation showed dramatically reduced tumor cellularity, proliferation, and pERK expression as well as induction of apoptosis. Gene Sets Enrichment Analysis (GSEA) revealed significant downregulations of E2F targets (NES=-1.9, p-adj=0.06) and the newly developed RAS/ERK (NES=-2.3, p-adj=0.06) gene set, consistent with the observed decrease in cell proliferation. There was marked upregulation of EMT (NES=2.7, FDR<0.001) and TGF-{beta} signaling (NES=2.3, FDR=0.004) in remaining tumor cells, suggesting these pathways could confer resistance. scRNA-seq analysis of TME showed dramatic shifts in cancer-associated fibroblasts (CAFs), with KRAS inhibition driving a shift from normal fibroblasts to inflammatory CAFs, and upregulation of interferon alpha and gamma pathways, suggesting that KRAS inhibition can activate innate immune response in the setting of peritoneal metastases. In a cohort of 6 heavily pre-treated patients with AA treated with KRAS inhibitors (1 G12D, 3 G12C, 2 pan-KRAS), all had biochemical response based on CEA/Ca19-9 or ctDNA and clinical benefit by RECIST criteria (1 CR, 1 PR, 4 SD). ConclusionsWhile effective suppression of RAS/ERK signaling by KRAS inhibitors reduces tumor growth, adaptive activation of EMT and TGF-{beta} pathways may mediate resistance in KRASmut AA. Additionally, KRAS inhibition remodels TME and may enhance innate immune signaling. These findings support continued clinical development of KRAS inhibitors in AA and provide a rationale for combination strategies targeting resistance pathways and stromal remodeling.

cancer biology↗

bioRxiv2021

Oncogenic KRAS Requires Complete Loss of BAP1 Function for Development of Murine Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is a primary biliary malignancy that harbors a dismal prognosis. Oncogenic mutations of KRAS and loss of function mutations of BRCA1-associated protein 1 (BAP1) have been identified as recurrent somatic alterations in ICC. However, an autochthonous genetically engineered mouse model of ICC that genocopies the co-occurrence of these mutations has never been developed. By crossing Albumin-Cre mice bearing conditional alleles of mutant Kras and/or floxed Bap1, Cre-mediated recombination within the liver was induced. Mice with hepatic expression of mutant KrasG12D alone (KA), bi-allelic loss of hepatic Bap1 (BhomoA), and heterozygous loss of Bap1 in conjunction with mutant KrasG12D expression (BhetKA) developed primary hepatocellular carcinoma (HCC), but no discernible ICC. In contrast, mice with homozygous loss of Bap1 in conjunction with mutant KrasG12D expression (BhomoKA) developed discrete foci of HCC and ICC. Further, the median survival of BhomoKA mice was significantly shorter at 24 weeks, when compared to median survival of [≥]40 weeks in BhetKA mice and approximately 50 weeks in BhomoA and KA mice (p <0.001). Microarray analysis performed on liver tissue from KA and BhomoKA mice identified differentially expressed genes in the setting of BAP1 loss and suggests that deregulation of ferroptosis might be one mechanism by which loss of BAP1 cooperates with oncogenic Ras in hepato-biliary carcinogenesis. Our autochthonous model provides an in vivo platform to further study this lethal class of neoplasm.

cell biology↗