Allosteric SHP2 inhibition increases apoptotic dependency on BCL2 and synergizes with venetoclax in FLT3- and KIT-mutant AML.

Mutations in the receptor tyrosine kinases (RTKs) FLT3 and KIT are frequent and associated with poor outcomes in acute myeloid leukemia (AML). Although selective FLT3 inhibitors (FLT3i) are clinically effective, remissions are short-lived due to secondary resistance characterized by acquired mutations constitutively activating the RAS/MAPK pathway. Hereby, we report the pre-clinical efficacy of co-targeting SHP2, a critical node in MAPK signaling, and BCL2 in RTK-driven AML. The allosteric SHP2 inhibitor RMC-4550 suppresses proliferation of AML cell lines with FLT3 and KIT mutations, including cell lines with acquired resistance to FLT3i. We demonstrate that pharmacologic SHP2 inhibition unveils an Achilles' heel of RTK-driven AML, increasing apoptotic dependency on BCL2 via MAPK-dependent mechanisms, including upregulation of BMF and downregulation of MCL1. Consequently, RMC-4550 and venetoclax are synergistically lethal in AML cell lines and in clinically relevant xenograft models. Our results provide mechanistic rationale and pre-clinical evidence for co-targeting SHP2 and BCL2 in RTK-driven AML.

RAS nucleotide cycling underlies the SHP2 phosphatase dependence of mutant BRAF-, NF1- and RAS-driven cancers.

Oncogenic alterations in the RAS/RAF/MEK/ERK pathway drive the growth of a wide spectrum of cancers. While BRAF and MEK inhibitors are efficacious against BRAFV600E-driven cancers, effective targeted therapies are lacking for most cancers driven by other pathway alterations, including non-V600E oncogenic BRAF, RAS GTPase-activating protein (GAP) NF1 (neurofibromin 1) loss and oncogenic KRAS. Here, we show that targeting the SHP2 phosphatase (encoded by PTPN11) with RMC-4550, a small-molecule allosteric inhibitor, is effective in human cancer models bearing RAS-GTP-dependent oncogenic BRAF (for example, class 3 BRAF mutants), NF1 loss or nucleotide-cycling oncogenic RAS (for example, KRASG12C). SHP2 inhibitor treatment decreases oncogenic RAS/RAF/MEK/ERK signalling and cancer growth by disrupting SOS1-mediated RAS-GTP loading. Our findings illuminate a critical function for SHP2 in promoting oncogenic RAS/MAPK pathway activation in cancers with RAS-GTP-dependent oncogenic BRAF, NF1 loss and nucleotide-cycling oncogenic KRAS. SHP2 inhibition is a promising molecular therapeutic strategy for patients with cancers bearing these oncogenic drivers.

The nuclear transport receptor Importin-11 is a tumor suppressor that maintains PTEN protein.

Phosphatase and tensin homologue (PTEN) protein levels are critical for tumor suppression. However, the search for a recurrent cancer-associated gene alteration that causes PTEN degradation has remained futile. In this study, we show that Importin-11 (Ipo11) is a transport receptor for PTEN that is required to physically separate PTEN from elements of the PTEN degradation machinery. Mechanistically, we find that the E2 ubiquitin-conjugating enzyme and IPO11 cargo, UBE2E1, is a limiting factor for PTEN degradation. Using in vitro and in vivo gene-targeting methods, we show that Ipo11 loss results in degradation of Pten, lung adenocarcinoma, and neoplasia in mouse prostate with aberrantly high levels of Ube2e1 in the cytoplasm. These findings explain the correlation between loss of IPO11 and PTEN protein in human lung tumors. Furthermore, we find that IPO11 status predicts disease recurrence and progression to metastasis in patients choosing radical prostatectomy. Thus, our data introduce the IPO11 gene as a tumor-suppressor locus, which is of special importance in cancers that still retain at least one intact PTEN allele.

Combinatorial Action of MicroRNAs let-7 and miR-34 Effectively Synergizes with Erlotinib to Suppress Non-small Cell Lung Cancer Cell Proliferation.

Lung cancer represents the leading cause of cancer-related deaths in men and women worldwide. Targeted therapeutics, including the epidermal growth factor receptor (EGFR) inhibitor erlotinib, have recently emerged as clinical alternatives for the treatment of non-small cell lung cancer (NSCLC). However, the development of therapeutic resistance is a major challenge, resulting in low 5-year survival rates. Due to their ability to act as tumor suppressors, microRNAs (miRNAs) are attractive candidates as adjuvant therapeutics for the treatment of NSCLC. In this study, we examine the ability of 2 tumor suppressor miRNAs, let-7b and miR-34a to sensitize KRAS;TP53 mutant non-small cell lung cancer cells to the action of erlotinib. Treatment with these miRNAs, individually or in combination, resulted in synergistic potentiation of the anti-proliferative effects of erlotinib. This effect was observed over a wide range of miRNA and erlotinib interactions, suggesting that let-7b and miR-34a target oncogenic pathways beyond those inhibited by EGFR. Combinatorial treatment with let-7b and miR-34a resulted in the strongest synergy with erlotinib, indicating that these miRNAs can effectively target multiple cellular pathways involved in cancer cell proliferation and resistance to erlotinib. Together, our findings indicate that NSCLC cells can be effectively sensitized to erlotinib by supplementation with tumor suppressor miRNAs, and suggest that the use of combinations of miRNAs as adjuvant therapeutics for the treatment of lung cancer is a viable clinical strategy.

Rapid in vivo validation of candidate drivers derived from the PTEN-mutant prostate metastasis genome.

Human genome analyses have revealed that increasing gene copy number alteration is a driving force of incurable cancer of the prostate (CaP). Since most of the affected genes are hidden within large amplifications or deletions, there is a need for fast and faithful validation of drivers. However, classic genetic CaP engineering in mouse makes this a daunting task because generation, breeding based combination of alterations and non-invasive monitoring of disease are too time consuming and costly. To address the unmet need, we recently developed RapidCaP mice, which endogenously recreate human PTEN-mutant metastatic CaP based on Cre/Luciferase expressing viral infection, that is guided to Pten(loxP)/Trp53(loxP) prostate. Here we use a sensitized, non-metastatic Pten/Trp53-mutant RapidCaP system for functional validation of human metastasis drivers in a much accelerated time frame of only 3-4months. We used in vivo RNAi to target three candidate tumor suppressor genes FOXP1, RYBP and SHQ1, which reside in a frequent deletion on chromosome 3p and show that Shq1 cooperates with Pten and p53 to suppress metastasis. Our results thus demonstrate that the RapidCaP system forms a much needed platform for in vivo screening and validation of genes that drive endogenous lethal CaP.

MicroRNAs and the cancer phenotype: profiling, signatures and clinical implications.

MicroRNAs (miRNAs) have emerged as key genetic regulators of a wide variety of biological processes, including growth, proliferation, and survival. Recent advances have led to the recognition that miRNAs can act as potent oncogenes and tumor suppressors, playing crucial roles in the initiation, maintenance, and progression of the oncogenic state in a variety of cancers. Determining how miRNA expression and function is altered in cancer is an important goal, and a necessary prerequisite to the development and adoption of miRNA-based therapeutics in the clinic. Highly promising clinical applications of miRNAs are the use of miRNA signatures as biomarkers for cancer (for example, for early detection or diagnosis), and therapeutic supplementation or inhibition of specific miRNAs to alter the cancer phenotype. In this review, we discuss the main methods used for miRNA profiling, and examine key miRNAs that are commonly altered in a variety of tumors. Current studies underscore the functional versatility and potency of miRNAs in various aspects of the cancer phenotype, pointing to their potential clinical applications. Consequently, we discuss the application of miRNAs as biomarkers, clinical agents, and therapeutic targets, highlighting both the enormous potential and major challenges in this field.

miR-1 and miR-206 regulate angiogenesis by modulating VegfA expression in zebrafish.

Cellular communication across tissues is an essential process during embryonic development. Secreted factors with potent morphogenetic activity are key elements of this cross-talk, and precise regulation of their expression is required to elicit appropriate physiological responses. MicroRNAs (miRNAs) are versatile post-transcriptional modulators of gene expression. However, the large number of putative targets for each miRNA hinders the identification of physiologically relevant miRNA-target interactions. Here we show that miR-1 and miR-206 negatively regulate angiogenesis during zebrafish development. Using target protectors, our results indicate that miR-1/206 directly regulate the levels of Vascular endothelial growth factor A (VegfA) in muscle, controlling the strength of angiogenic signaling to the endothelium. Conversely, reducing the levels of VegfAa, but not VegfAb, rescued the increase in angiogenesis observed when miR-1/206 were knocked down. These findings uncover a novel function for miR-1/206 in the control of developmental angiogenesis through the regulation of VegfA, and identify a key role for miRNAs as regulators of cross-tissue signaling.