Oncogenic KRAS is the key driver oncogene for several of the most aggressive human cancers. One key feature of oncogenic KRAS expression is an early increase in cellular reactive oxygen species (ROS) which promotes cellular transformation if cells manage to escape cell death, mechanisms of which remain incompletely understood. Here, we identify that expression of oncogenic as compared to WT KRAS in isogenic cellular systems renders cells more resistant to ferroptosis, a recently described type of regulated necrosis. Mechanistically, we find that cells with mutant KRAS show a specific lack of ferroptosis-induced lipid peroxidation. Interestingly, KRAS-mutant cells upregulate expression of ferroptosis suppressor protein 1 (FSP1). Indeed, elevated levels of FSP1 in KRAS-mutant cells are responsible for mediating ferroptosis resistance and FSP1 is upregulated as a consequence of MAPK and NRF2 pathway activation downstream of KRAS. Strikingly, FSP1 activity promotes cellular transformation in soft agar and its overexpression is sufficient to promote spheroid growth in 3D in KRAS WT cells. Moreover, FSP1 expression and its activity in ferroptosis inhibition accelerates tumor onset of KRAS WT cells in the absence of oncogenic KRAS in vivo. Consequently, we find that pharmacological induction of ferroptosis in pancreatic organoids derived from the LsL-KRAS^G12D expressing mouse model is only effective in combination with FSP1 inhibition. Lastly, FSP1 is upregulated in non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) as compared to the respective normal tissue of origin and correlates with NRF2 expression in PDAC patient datasets. Based on these data, we propose that KRAS-mutant cells must navigate a ferroptosis checkpoint by upregulating FSP1 during tumor establishment. Consequently, ferroptosis-inducing therapy should be combined with FSP1 inhibitors for efficient therapy of KRAS-mutant cancers.

Purpose: Recurrent tumors (RTs) of head and neck squamous cell carcinoma (HNSCC) occur in up to 60% with poor therapeutic response and detrimental prognosis. We hypothesized that HNSCC RTs successfully evade anti-tumor immune response and aimed to reveal tumor immune microenvironment (TIME) changes of primary tumors (PTs) and corresponding RTs. Experimental Design: Tumor infiltrating leukocytes (TILs) of 300 PTs and 108 RTs from two large, independent and clinically well-characterized HNSCC cohorts (discovery cohort/DC, validation cohort/VD) were compared by immunohistochemistry. mRNA expression analysis of 730 immune-related genes was performed for 18 PTs and RTs after adjuvant chemoradiotherapy (CRT). The effect of chemotherapy- and radiation-resistance was assessed with an in vitro spheroid/immunocyte coculture model. Results: TIME analysis revealed overall decrease of TILs with significant loss of CD8+ T-cells (DC p=0.045/VC p<0.0001) and B-lymphocytes (DC p=0.036/VC p<0.0001) in RTs compared to PTs in both cohorts. Decrease predominantly occurred in RTs after CRT. Gene expression analysis confirmed loss of TILs (p=0.0004) and B-lymphocytes (p<0.0001) and showed relative increase of neutrophils (p=0.018), macrophages (p<0.0001), dendritic cells (p=0.0002) and mast cells (p=0.0057) as well as lower overall expression of immune related genes (p=0.018) in RTs after CRT. Genes involved in B-lymphocyte functions and number of tertiary lymphoid structures showed the strongest decrease. SPP1 and MAPK1 were upregulated in vivo and in vitro indicating their potential suitability as therapeutic targets in CRT resistance. Conclusions: HNSCC RTs have an immunosuppressive TIME, which is particularly apparent after adjuvant CRT and might substantially contribute to poor therapeutic response and prognosis.

Small cell lung cancer (SCLC) is a highly aggressive type of lung cancer, characterized by rapid proliferation, early metastatic spread, frequent early relapse and a high mortality rate ^1–3 . Recent evidence has suggested that innervation has an important role in the development and progression of several types of cancer ^4,5 . Cancer-to-neuron synapses have been reported in gliomas ^6,7 , but whether peripheral tumours can form such structures is unknown. Here we show that SCLC cells can form functional synapses and receive synaptic transmission. Using in vivo insertional mutagenesis screening in conjunction with cross-species genomic and transcriptomic validation, we identified neuronal, synaptic and glutamatergic signalling gene sets in mouse and human SCLC. Further experiments revealed the ability of SCLC cells to form synaptic structures with neurons in vitro and in vivo. Electrophysiology and optogenetic experiments confirmed that cancer cells can receive NMDA receptor- and GABA _A receptor-mediated synaptic inputs. Fitting with a potential oncogenic role of neuron–SCLC interactions, we showed that SCLC cells derive a proliferation advantage when co-cultured with vagal sensory or cortical neurons. Moreover, inhibition of glutamate signalling had therapeutic efficacy in an autochthonous mouse model of SCLC. Therefore, following malignant transformation, SCLC cells seem to hijack synaptic signalling to promote tumour growth, thereby exposing a new route for therapeutic intervention.

Kinase inhibitors suppress the growth of oncogene driven cancer but also enforce the selection of treatment resistant cells that are thought to promote tumor relapse in patients. Here, we report transcriptomic and functional genomics analyses of cells and tumors within their microenvironment across different genotypes that persist during kinase inhibitor treatment. We uncover a conserved, MAPK/IRF1-mediated inflammatory response in tumors that undergo stemness- and senescence-associated reprogramming. In these tumor cells, activation of the innate immunity sensor RIG-I via its agonist IVT4, triggers an interferon and a pro-apoptotic response that synergize with concomitant kinase inhibition. In humanized lung cancer xenografts and a syngeneic Egfr-driven lung cancer model these effects translate into reduction of exhausted CD8⁺ T cells and robust tumor shrinkage. Overall, the mechanistic understanding of MAPK/IRF1-mediated intratumoral reprogramming may ultimately prolong the efficacy of targeted drugs in genetically defined cancer patients.

An examination of the activity profiles of RET inhibitors suggests potential treatment for RET -rearranged cancers.

Background & aims Gallbladder cancer (GBC) is a highly aggressive malignancy of the biliary tract. Most cases of GBC are diagnosed in low‐ and middle‐income countries and research into this disease has long been limited. In this study we therefore investigate the epigenetic changes along the model of GBC carcinogenesis represented by the sequence gallstone disease → dysplasia → GBC in Chile, the country with the highest incidence of GBC worldwide. Approach To perform epigenome‐wide methylation profiling, genomic DNA extracted from sections of FFPE gallbladder tissue was analyzed using Illumina Infinium MethylationEPIC BeadChips. Pre‐processed, quality‐controlled data from 82 samples (gallstones n=32, low‐grade dysplasia n=13, high‐grade dysplasia n=9, GBC n=28) were available to identify differentially methylated markers, regions, and pathways as well as changes in copy number variations (CNVs). Main results The number and magnitude of epigenetic changes increased with disease development and predominantly involved the hypermethylation of CpG islands and gene promoter regions. The methylation of genes implicated in Wnt signaling, Hedgehog signaling, and tumor suppression increased with tumor grade. CNVs also increased with GBC development and affected CDKN2A, MDM2, TP53, and CCND1. Gains in the targetable ERBB2 were detected in 14% of the GBC samples. Conclusions Our results indicate that GBC carcinogenesis comprises three main methylation stages: early (gallstone disease and low‐grade dysplasia), intermediate (high‐grade dysplasia), and late (GBC). The identified gradual changes in methylation and CNVs may help to enhance our understanding of the mechanisms underlying this aggressive disease and eventually lead to improved treatment and early diagnosis of GBC.