Baseline cellular state shapes the molecular impact of mutant Kirsten rat sarcoma viral oncogene homologue (KRAS) alleles in reconstituted pancreatic cancer cells.

Kirsten rat sarcoma viral oncogene homologue (KRAS) is mutated in over 90% of pancreatic ductal adenocarcinomas (PDAC), where hotspot alterations in codons 12, 13, and 61 drive tumour initiation and progression. Although distinct biochemical properties have been described for individual KRAS mutants, whether they generate unique allele-specific signalling programmes in PDAC cells remains unresolved. Here, we systematically interrogated the molecular consequences of seven common KRAS mutant variants in reconstituted isogenic, KRAS-deficient PDAC cell lines by integrated transcriptomic, proteomic, and phosphoproteomic profiling. We found that baseline cellular state, rather than allele identity, was the predominant driver of molecular variation. Comparisons with established KRAS reference signatures revealed significant but moderate overlap at the mRNA level and less so at the proteome level. Pathway analyses highlighted the interferon response and mitochondrial translation-related proteins as recurrently altered across mutant alleles, while phosphoproteomic data confirmed robust extracellular signal-regulated kinase 1/2 (ERK1/2) activity and the suppression of dual-specificity tyrosine phosphorylation-regulated kinase substrates by mutant KRAS expression. Importantly, no robust mutant allele-specific molecular programmes were identified in our KRAS-reconstituted cell lines. Together, our study establishes a comprehensive multi-omics resource for KRAS signalling in PDAC and demonstrates that cellular context exerts a stronger influence than allele identity in shaping molecular profiles, with implications for interpreting putative allele-specific signalling dependencies.