Ras/MAPK signalling intensity defines subclonal fitness in a mouse model of hepatocellular carcinoma

Abstract

Quantitative differences in signal transduction are to date an understudied feature of tumour heterogeneity. The MAPK Erk pathway, which is activated in a large proportion of human tumours, is a prototypic example of distinct cell fates being driven by signal intensity. We have used primary hepatocyte precursors transformed with different dosages of an oncogenic form of Ras to model subclonal variations in MAPK signalling. Orthotopic allografts of Ras-transformed cells in immunocompromised mice gave rise to fast-growing aggressive tumours, both at the primary location and in the peritoneal cavity. Fluorescent labelling of cells expressing different oncogene levels, and consequently varying levels of MAPK Erk activation, highlighted the selection processes operating at the two sites of tumour growth. Indeed, significantly higher Ras expression was observed in primary as compared to secondary, metastatic sites, despite the apparent evolutionary trade-off of increased apoptotic death in the liver that correlated with high Ras dosage. Analysis of the immune tumour microenvironment at the two locations suggests that fast peritoneal tumour growth in the immunocompromised setting is abrogated in immunocompetent animals due to efficient antigen presentation by peritoneal dendritic cells. Furthermore, our data indicate that, in contrast to the metastatic-like outgrowth, strong MAPK signalling is required in the primary liver tumours to resist elimination by NK cells. Overall, this study describes a quantitative aspect of tumour heterogeneity and points to a potential vulnerability of a subtype of hepatocellular carcinoma as a function of MAPK Erk signalling intensity.

Cancer cell genetics shaping of the tumor microenvironment reveals myeloid cell-centric exploitable vulnerabilities in hepatocellular carcinoma

“…Furthermore, we mimicked the activation of the MAPK signaling pathway (aberrantly activated in ~50% of HCCs 46 ) using constitutive expression of the proto-oncogene Ras. In light of the evident differences in MAPK activation states and cancer malignant features incumbered by distinct Ras isoforms and point mutations in several cancers [50][51][52][53][54] , including HCCs 28,41,55 , we employed distinct oncogenic mutations of Nras: Nras G12D (pT3-Nras G12D -GFP) and Nras G12V (pT/CaggsNras G12V -IRES-Luc), to generate two additional HCC models, both combined with Pten loss.…”

“…In HCC and other solid tumor types, well-established oncogenic signals such as Myc [16][17][18][19] , Wnt/β-Catenin 12,20,21 , Ras-MAPK-ERK pathway activation or loss of the tumor suppressor gene Tp53 [22][23][24][25][26] distinctively reprogram the liver local and systemic environment through either promoting inflammation, immunosuppression or dampening anti-tumor immunity 27 . Importantly, quantitative differences in the Ras-MAPK-ERK signaling pathway activation state can exert unique biological consequences in response to extrinsic cues specific to different TMEs 28 . Yet, the non-cell autonomous effects and cellular mediators ensuing oncogenic pathways activation threshold that may dictate the HCC TME landscape remain to be identified.…”

Cancer cell genetics shaping of the tumor microenvironment reveals myeloid cell-centric exploitable vulnerabilities in hepatocellular carcinoma

“…Furthermore, we mimicked the activation of the mitogen-activated protein kinase (MAPK) signaling pathway (aberrantly activated in ~50% of HCCs 46 ) using constitutive expression of the protooncogene RAS. In light of the evident differences in MAPK activation states and cancer malignant features incumbered by distinct Ras isoforms and point mutations in several cancers [50][51][52][53][54] , including HCCs 28,41,55 , we employed distinct oncogenic mutations of Nras: Nras G12D (pT3-Nras G12D -GFP) and Nras G12V (pT/CaggsNras G12V -IRES-Luc), to generate two additional HCC models, both combined with Pten loss.…”

“…In HCCs and other solid tumor types, well-established oncogenic signals such as MYC [16][17][18][19] , Wnt/ β-Catenin 12,20,21 , Ras-MAPK-ERK pathway activation or loss of the tumor suppressor gene TP53 [22][23][24][25][26] distinctively reprogram the liver local and systemic environment through either promoting inflammation, immunosuppression or dampening anti-tumor immunity 27 . Importantly, quantitative differences in the Ras-MAPK-ERK signaling pathway activation state can exert unique biological consequences in response to extrinsic cues specific to different TME 28 . Yet, the non-cell autonomous effects and cellular mediators ensuing oncogenic pathways activation threshold that may dictate the HCC TME landscape remain to be elucidated.…”