PDAC Models with KRASG12R Show Elevated MHC Class I Expression

Author

• Elina Lynge Wagner, University of Nebraska Medical CenterFollow

ORCID ID

0009-0005-2207-8735

Graduation Date

Spring 5-9-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Programs

Cancer Research

First Advisor

Michael A. Hollingsworth

Second Advisor

Joyce Solheim

Third Advisor

Geoffrey Thiele

Abstract

Pancreatic cancer, the third leading cause of cancer-related deaths in the United States, carries a dismal 5-year survival rate of ~13%. Oncogenic KRAS mutations drive >90% of pancreatic ductal adenocarcinoma cases, with KRAS^G12D, KRAS^G12V, and KRAS^G12R predominating. Canonical KRAS^G12D strongly activates PI3K-AKT signaling via direct p110α binding, which represses MHC class I (MHC-I) expression and antigen presentation. In contrast, atypical KRAS^G12R exhibits structural disruption in its Switch-II region, a single α-helical turn compared to the typical four, impairing p110α interaction and shifting toward KRAS-independent PI3K signaling via upregulated p110γ. KRAS^G12R tumors also display increased immune cell infiltration (B cells, M2 macrophages CD4⁺ T cells, and CD8⁺ T cells), suggesting enhanced immunogenicity.

This thesis tested two hypotheses: (1) KRAS^G12R-expressing cells have higher baseline MHC-I than KRAS^G12D-expressing cells, and (2) Downstream PI3K signaling differences drive this effect. In doxycycline-inducible HPNE cells (expressing EV, KRAS^WT, KRAS^G12D, or KRAS^G12R), flow cytometry and RT-qPCR revealed consistently higher MHC-I (HLA-A, -B, -C) in KRAS^G12R compared to KRAS^G12D across multiple time points. Statistically significant differences emerged in untreated and RMC-6236 treated doxycycline-inducible HPNE cells at multiple time points. Trends consistently favored KRAS^G12R even when non-significant. Notably, AsPC-1 cells exhibited lower surface MHC-I expression despite comparable HLA-A transcripts.

PI3K signaling was assessed via isoform-specific inhibitors (A66 [p110α], IPI-549 [p110γ]) and western blots (p-mTOR Ser2448, p-AKT Ser473/Thr308, p-STAT1 Ser727/Tyr701). RMC-6236 reduced PI3K pathway phosphorylation while increasing MHC-I expression in all cell lines. However, A66 and IPI-549 produced minimal signaling and MHC-I changes, indicating PI3K isoform differences may not be the primary driver of the KRAS^G12R-induced increase in MHC-I.

Collectively, KRAS^G12R-positive cells exhibited elevated MHC-I expression even with RMC-6236 treatment, suggesting that these differences are not solely driven by PI3K signaling. Minimal effects from p110α and p110γ inhibition further support a PI3K-independent component underlying this phenotype. Together with RMC-6236’s broad MHC-I upregulation across variants, these findings indicate that KRAS^G12R-expressing tumors may possess distinct immunogenicity, warranting further investigation into mutation-specific immune regulation and subtype-tailored immunotherapy strategies.

Rights

The author holds the copyright to this work and any reuse or permissions must be obtained from the author directly.

Recommended Citation

Wagner, Elina Lynge, "PDAC Models with KRASG12R Show Elevated MHC Class I Expression" (2026). Theses & Dissertations. 1046.
https://digitalcommons.unmc.edu/etd/1046