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 prostate cancer (PC). 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 PC 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 PC based on Cre/Luciferase expressing viral infection, that is guided to PtenloxP/Trp53loxP 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 3-4 months. 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 PC

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

Flawed experimental design reveals the need for guidelines requiring appropriate positive controls in endocrine disruption research

A study published in Toxicological Sciences (Ryan et al., 2009) illustrates the importance of examining appropriate doses of both the positive control and the test chemical in research on endocrine-disrupting chemicals. For the three low doses of bisphenol A (BPA) that were fed to rats during pregnancy and lactation, there were no effects on female offspring (there were also no effects on male offspring from the same experiment; Howdeshell et al., 2008). A review of the results of the positive control doses makes it clear that the experiment cannot adequately assess the consequences of low-dose exposure to BPA because the animal model is insensitive to low doses of the positive control estrogen. Therefore, conclusions being drawn from this experiment about low-dose responses to any estrogen are invalid, including that of “no harm” from the low doses of BPA that were tested. However, the experiment is important because it highlights the need to apply basic principles of study design, long known and accepted in studies of hormones and hormonally active drugs, to toxicological studies of chemicals with hormonal activity