Novel RAF-directed approaches to overcome current clinical limits and block the RAS/RAF node.

Mutations in the RAS-RAF-MEK-ERK pathway are frequent alterations in cancer and RASopathies, and while RAS oncogene activation alone affects 19% of all patients and accounts for approximately 3.4 million new cases every year, less frequent alterations in the cascade's downstream effectors are also involved in cancer etiology. RAS proteins initiate the signaling cascade by promoting the dimerization of RAF kinases, which can act as oncoproteins as well: BRAFV600E is the most common oncogenic driver, mutated in the 8% of all malignancies. Research in this field led to the development of drugs that target the BRAFV600-like mutations (Class I), which are now utilized in clinics, but cause paradoxical activation of the pathway and resistance development. Furthermore, they are ineffective against non-BRAFV600E malignancies that dimerize and could be either RTK/RAS independent or dependent (Class II and III, respectively), which are still lacking an effective treatment. This review discusses the recent advances in anti-RAF therapies, including paradox breakers, dimer-inhibitors, immunotherapies, and other novel approaches, critically evaluating their efficacy in overcoming the therapeutic limitations, and their putative role in blocking the RAS pathway.

Resistance to KRAS G12C Inhibition in Non-small Cell Lung Cancer.

PURPOSE OF REVIEW: Although the recent development of direct KRASG12C inhibitors (G12Ci) has improved outcomes in KRAS mutant cancers, responses occur only in a fraction of patients, and among responders acquired resistance invariably develops over time. Therefore, the characterization of the determinants of acquired resistance is crucial to inform treatment strategies and to identify novel therapeutic vulnerabilities that can be exploited for drug development. RECENT FINDINGS: Mechanisms of acquired resistance to G12Ci are heterogenous including both on-target and off-target resistance. On-target acquired resistance includes secondary codon 12 KRAS mutations, but also acquired codon 13 and codon 61 alterations, and mutations at drug binding sites. Off-target acquired resistance can derive from activating mutations in KRAS downstream pathway (e.g., MEK1), acquired oncogenic fusions (EML4-ALK, CCDC176-RET), gene level copy gain (e.g., MET amplification), or oncogenic alterations in other pro-proliferative and antiapoptotic pathways (e.g., FGFR3, PTEN, NRAS). In a fraction of patients, histologic transformation can also contribute to the development of acquire resistance. We provided a comprehensive overview of the mechanisms that limit the efficacy of this G12i and reviewed potential strategies to overcome and possibly delay the development of resistance in patients receiving KRAS directed targeted therapies.

The phospholipid transporter PITPNC1 links KRAS to MYC to prevent autophagy in lung and pancreatic cancer.

BACKGROUND: The discovery of functionally relevant KRAS effectors in lung and pancreatic ductal adenocarcinoma (LUAD and PDAC) may yield novel molecular targets or mechanisms amenable to inhibition strategies. Phospholipids availability has been appreciated as a mechanism to modulate KRAS oncogenic potential. Thus, phospholipid transporters may play a functional role in KRAS-driven oncogenesis. Here, we identified and systematically studied the phospholipid transporter PITPNC1 and its controlled network in LUAD and PDAC. METHODS: Genetic modulation of KRAS expression as well as pharmacological inhibition of canonical effectors was completed. PITPNC1 genetic depletion was performed in in vitro and in vivo LUAD and PDAC models. PITPNC1-deficient cells were RNA sequenced, and Gene Ontology and enrichment analyses were applied to the output data. Protein-based biochemical and subcellular localization assays were run to investigate PITPNC1-regulated pathways. A drug repurposing approach was used to predict surrogate PITPNC1 inhibitors that were tested in combination with KRASG12C inhibitors in 2D, 3D, and in vivo models. RESULTS: PITPNC1 was increased in human LUAD and PDAC, and associated with poor patients' survival. PITPNC1 was regulated by KRAS through MEK1/2 and JNK1/2. Functional experiments showed PITPNC1 requirement for cell proliferation, cell cycle progression and tumour growth. Furthermore, PITPNC1 overexpression enhanced lung colonization and liver metastasis. PITPNC1 regulated a transcriptional signature which highly overlapped with that of KRAS, and controlled mTOR localization via enhanced MYC protein stability to prevent autophagy. JAK2 inhibitors were predicted as putative PITPNC1 inhibitors with antiproliferative effect and their combination with KRASG12C inhibitors elicited a substantial anti-tumour effect in LUAD and PDAC. CONCLUSIONS: Our data highlight the functional and clinical relevance of PITPNC1 in LUAD and PDAC. Moreover, PITPNC1 constitutes a new mechanism linking KRAS to MYC, and controls a druggable transcriptional network for combinatorial treatments.

How to manage KRAS G12C-mutated advanced non-small-cell lung cancer.

Constitutive KRAS signalling drives tumorigenesis across several cancer types. In non-small-cell lung cancer (NSCLC) activating KRAS mutations occur in ~30% of cases, and the glycine to cysteine substitution at codon 12 (G12C) is the most common KRAS alteration. Although KRAS mutations have been considered undruggable for over 40 years, the recent discovery of allelic-specific KRAS inhibitors has paved the way to personalized cancer medicine for patients with tumours harbouring these mutations. Here, we review the current treatment landscape for patients with advanced NSCLCs harbouring a KRAS G12C mutation, including PD-(L) 1-based therapies and direct KRAS inhibitors as well as sequential treatment options. We also explore the possible mechanisms of resistance to KRAS inhibition and strategies to overcome resistance in patients with KRAS G12C-mutant NSCLC.