{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T03:01:48Z","timestamp":1790564508677,"version":"4.1.0"},"reference-count":18,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2026,1,23]],"date-time":"2026-01-23T00:00:00Z","timestamp":1769126400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["RS-2023-00279934"],"award-info":[{"award-number":["RS-2023-00279934"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Colorectal cancer (CRC) remains a major cause of cancer-related deaths in advanced disease, and activating KRAS\/NRAS mutations limit the use of anti-EGFR antibodies to RAS\u2013wild-type tumors. The cellular prion protein (PrPC) has been linked to aggressive and chemoresistant CRC, but its extracellular partners and functional relevance in KRAS-mutant disease are not fully defined. Here, we examined extracellular PrPC complexes and PrPC-associated signaling in CRC cell lines and xenografts using a neutralizing PrPC monoclonal antibody. Across a CRC panel that included SNU-C5\/WT and its 5-fluorouracil- and oxaliplatin-resistant derivatives, HT-29 (KRAS\u2013wild-type), and HCT-8 and LoVo (KRAS-mutant), co-immunoprecipitation showed that PrPC forms complexes with the 37\/67 kDa laminin receptor (RPSA), with PrPC\u2013RPSA association particularly increased in KRAS-mutant HCT-8 and LoVo cells. PrPC protein levels were higher in KRAS-mutant HCT-8, SW620, and SNU-407 cells than in HT-29, and PrPC neutralization reduced viability in all four lines. Accordingly, we assessed upstream RAS activity and found that active RAS (RAS-GTP) was higher in KRAS-mutant cells than in HT-29, and PrPC treatment was associated with reduced RAS-GTP levels. In the same KRAS-mutant setting, basal AKT phosphorylation exceeded that in HT-29, and PrPC treatment lowered AKT phosphorylation without changing total AKT. Moreover, PrPC treatment was associated with reduced ERK1\/2 phosphorylation in KRAS-mutant cells, suggesting attenuation of downstream RAS pathway output. These signaling changes coincided with a decrease in the S-phase fraction and an increase in G1. In an HCT-8 (KRAS G13D) xenograft model, PrPC monotherapy inhibited tumor growth in a dose-dependent manner, and 5-fluorouracil (5-FU) monotherapy produced an intermediate effect. The combination of PrPC (10 mg\/kg) and 5-FU (20 mg\/kg) yielded the greatest tumor growth inhibition among the tested regimens. Consistent with this enhanced tumor control, immunofluorescence of xenograft tissues showed that PrPC, particularly with 5-FU, reduced intratumoral PrPC and PCNA and decreased CD31-positive microvessels and \u03b1-SMA\u2013positive vessel structures. Taken together, these findings suggest that extracellular PrPC supports RAS\u2013AKT signaling, proliferation, and tumor-associated angiogenesis in KRAS-mutant colorectal cancer, and that PrPC neutralization additively enhances 5-fluorouracil activity in KRAS-mutant models. The data provide a preclinical basis for evaluating PrPC antibodies in combination with fluoropyrimidine-based regimens in patients with KRAS-mutant CRC.<\/jats:p>","DOI":"10.3390\/ijms27031159","type":"journal-article","created":{"date-parts":[[2026,1,23]],"date-time":"2026-01-23T13:55:34Z","timestamp":1769176534000},"page":"1159","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["PrPC-Neutralizing Antibody Confers an Additive Benefit in Combination with 5-Fluorouracil in KRAS-Mutant Colorectal Cancer Models, Associated with Reduced RAS-GTP and AKT\/ERK Phosphorylation"],"prefix":"10.3390","volume":"27","author":[{"given":"Jeong Kun","family":"Lee","sequence":"first","affiliation":[{"name":"Program in Biomedical Science & Engineering, Department of Biomedical Sciences, College of Medicine, Inha University, 3-ga, Sinheung-dong, Jung-gu, Incheon 22332, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jun Young","family":"Yoon","sequence":"additional","affiliation":[{"name":"Program in Biomedical Science & Engineering, Department of Biomedical Sciences, College of Medicine, Inha University, 3-ga, Sinheung-dong, Jung-gu, Incheon 22332, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jae Young","family":"Lee","sequence":"additional","affiliation":[{"name":"Program in Biomedical Science & Engineering, Department of Biomedical Sciences, College of Medicine, Inha University, 3-ga, Sinheung-dong, Jung-gu, Incheon 22332, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6713-8229","authenticated-orcid":false,"given":"Sang Hun","family":"Lee","sequence":"additional","affiliation":[{"name":"Program in Biomedical Science & Engineering, Department of Biomedical Sciences, College of Medicine, Inha University, 3-ga, Sinheung-dong, Jung-gu, Incheon 22332, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1757","DOI":"10.1056\/NEJMoa0804385","article-title":"K-ras mutations and benefit from cetuximab in advanced colorectal cancer","volume":"359","author":"Karapetis","year":"2008","journal-title":"N. Engl. J. Med."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1023","DOI":"10.1056\/NEJMoa1305275","article-title":"Panitumumab\u2013FOLFOX4 treatment and RAS mutations in colorectal cancer","volume":"369","author":"Douillard","year":"2013","journal-title":"N. Engl. J. Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"10","DOI":"10.1016\/j.annonc.2022.10.003","article-title":"Metastatic colorectal cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up","volume":"34","author":"Cervantes","year":"2023","journal-title":"Ann. Oncol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"5863","DOI":"10.1093\/emboj\/20.21.5863","article-title":"The 37-kDa\/67-kDa laminin receptor acts as the cell-surface receptor for the cellular prion protein","volume":"20","author":"Gauczynski","year":"2001","journal-title":"EMBO J."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"725","DOI":"10.1002\/1878-0261.12411","article-title":"EGFR and Prion protein promote signaling via FOXO3a-KLF5 resulting in clinical resistance to platinum agents in colorectal cancer","volume":"13","author":"Atkinson","year":"2019","journal-title":"Mol. Oncol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1016\/j.ebiom.2019.07.036","article-title":"The cellular prion protein controls the mesenchymal-like molecular subtype and predicts disease outcome in colorectal cancer","volume":"46","author":"Ghazi","year":"2019","journal-title":"eBioMedicine"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"5876","DOI":"10.1093\/emboj\/20.21.5876","article-title":"Identification of interaction domains of the prion protein with its 37-kDa\/67-kDa laminin receptor","volume":"20","author":"Hundt","year":"2001","journal-title":"EMBO J."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"3459","DOI":"10.21873\/anticanres.15133","article-title":"PrPC Regulates the cancer stem cell properties via interaction with c-Met in colorectal cancer cells","volume":"41","author":"Lim","year":"2021","journal-title":"Anticancer Res."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"441","DOI":"10.1007\/s10585-016-9788-8","article-title":"Prion protein binding to HOP modulates the migration and invasion of colorectal cancer cells","volume":"33","author":"Giudice","year":"2016","journal-title":"Clin. Exp. Metastasis"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2682","DOI":"10.1158\/0008-5472.CAN-12-3759","article-title":"CD44-Positive cancer stem cells expressing cellular prion protein contribute to metastatic capacity in colorectal cancer","volume":"73","author":"Du","year":"2013","journal-title":"Cancer Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"313","DOI":"10.4062\/biomolther.2017.033","article-title":"Cellular prion protein enhances drug resistance of colorectal cancer cells via regulation of a survival signal pathway","volume":"26","author":"Lee","year":"2018","journal-title":"Biomol. Ther."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"6555","DOI":"10.1038\/onc.2017.263","article-title":"Role of HSPA1L as a cellular prion protein stabilizer in tumor progression via HIF-1\u03b1\/GP78 axis","volume":"36","author":"Lee","year":"2017","journal-title":"Oncogene"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"38638","DOI":"10.18632\/oncotarget.9575","article-title":"Cellular prion protein controls stem cell-like properties of human glioblastoma tumor-initiating cells","volume":"7","author":"Corsaro","year":"2016","journal-title":"Oncotarget"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Ryskalin, L., Biagioni, F., Busceti, C.L., Giambelluca, M.A., Morelli, L., Frati, A., and Fornai, F. (2021). The role of cellular prion protein in promoting stemness and differentiation in cancer. Cancers, 13.","DOI":"10.3390\/cancers13020170"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1080\/09687860500449994","article-title":"The prion protein and lipid rafts (Review)","volume":"23","author":"Taylor","year":"2006","journal-title":"Mol. Membr. Biol."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Shao, J., Choe, V., Cheng, H., Tsai, Y.C., Weissman, A.M., Luo, S., and Rao, H. (2014). Ubiquitin ligase gp78 targets unglycosylated prion protein PrP for ubiquitylation and degradation. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0092290"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"5342","DOI":"10.18632\/oncotarget.3028","article-title":"Induction of cellular prion protein (PrPc) under hypoxia inhibits apoptosis caused by TRAIL treatment","volume":"6","author":"Park","year":"2015","journal-title":"Oncotarget"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"41488","DOI":"10.18632\/oncotarget.9206","article-title":"Hypoxia regulates TRAIL sensitivity of colorectal cancer cells through mitochondrial autophagy","volume":"7","author":"Knoll","year":"2016","journal-title":"Oncotarget"}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/27\/3\/1159\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,29]],"date-time":"2026-01-29T10:09:13Z","timestamp":1769681353000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/27\/3\/1159"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,23]]},"references-count":18,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2026,2]]}},"alternative-id":["ijms27031159"],"URL":"https:\/\/doi.org\/10.3390\/ijms27031159","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,23]]}}}