Neuroblastoma is treated with aggressive multimodal therapy, yet more than 50% of patients experience relapse. We recently showed that relapsed neuroblastomas frequently harbor mutations leading to hyperactivated ERK signaling and sensitivity to MEK inhibition therapy. Here we sought to define a synergistic therapeutic partner to potentiate MEK inhibition. We first surveyed 22 genetically annotated human neuroblastoma-derived cell lines (from 20 unique patients) for sensitivity to the MEK inhibitor binimetinib. After noting an inverse correlation with sensitivity to ribociclib (CDK4/6 inhibitor), we studied the combinatorial effect of these two agents using proliferation assays, cell-cycle analysis, Ki67 immunostaining, time-lapse microscopy, and xenograft studies. Sensitivity to binimetinib and ribociclib was inversely related ( = -0.58, = 0.009). amplification status and expression were associated with ribociclib sensitivity and binimetinib resistance, whereas increased MAPK signaling was the main determinant of binimetinib sensitivity and ribociclib resistance. Treatment with both compounds resulted in synergistic or additive cellular growth inhibition in all lines tested and significant inhibition of tumor growth in three of four xenograft models of neuroblastoma. The augmented growth inhibition was attributed to diminished cell-cycle progression that was reversible upon removal of drugs. Here we demonstrate that combined binimetinib and ribociclib treatment shows therapeutic synergy across a broad panel of high-risk neuroblastoma preclinical models. These data support testing this combination therapy in relapsed high-risk neuroblastoma patients, with focus on cases with hyperactivated RAS-MAPK signaling. .

Bone resorption by osteoclasts is thought to promote the proliferation of prostate cancer cells disseminated to the skeleton (Mundy, 2002). Using a mouse model of experimental metastasis, we found that although latestage metastatic tumors were indeed surrounded by osteoclasts, these cells were spatially unrelated to the small foci of cancer cells in early-stage metastases. This is the first evidence that survival and growth of disseminated prostate cancer cells immediately after their extravasation may not depend on osteoclast involvement. Interestingly, prostate cancer cells expressing the a-receptor for platelet-derived growth factor (PDGFRa) progress during early-stages of skeletal dissemination, whereas cells expressing lower levels or lacking this receptor fail to survive after extravasation in the bone marrow. However, non-metastatic cells acquire bone-metastatic potential upon ectopic overexpression of PDGFRa. Finally, functional blockade of human PDGFRa on prostate cancer cells utilizing a novel humanized monoclonal antibodysoon to undergo phase-II clinical trials-significantly impairs the establishment of early skeletal metastases. In conclusion, our results strongly implicate PDGFRa in prostate cancer bone tropism through its promotion of survival and progression of early-metastatic foci, providing ground for therapeutic strategies aimed at preventing or containing the initial progression of skeletal metastases in patients affected by prostate adenocarcinoma.

<p>Supplementary Table 1 and Supplmentary Figures 1-3 Legends</p>

<p>CELSR3 is a target for T-cell redirection therapeutics. <b>A,</b> CELSR3xCD3 bs-mAb directs T-cell mediated cytotoxicity in CELSR3(+) TCCSUP NLR and PM154 NLR but not CELSR3(−) DU145 NLR, TCCSUP CELSR3 KO cell lines. 5:1 (exp. 1) or 10:1 (exp. 2) pan T cells to tumor cells were added to each well along with CELSR3xCD3 bs-mAb and imaged using the IncuCyte S3 platform. Maximum cell lysis occurred by day 7 timepoint. At least three biological replicates were analyzed from one independent experiment. <b>B,</b> Cell surface expression of CELSR3 on tumor cell lines determined by quantitative flow cytometry and calculated from at least 10,000 events per sample. Dotted line denotes assay lower limit of detection.</p>

<div><p>Although recent efforts have led to the development of highly effective androgen receptor (AR)-directed therapies for the treatment of advanced prostate cancer, a significant subset of patients will progress with resistant disease including AR-negative tumors that display neuroendocrine features [neuroendocrine prostate cancer (NEPC)]. On the basis of RNA sequencing (RNA-seq) data from a clinical cohort of tissue from benign prostate, locally advanced prostate cancer, metastatic castration-resistant prostate cancer and NEPC, we developed a multi-step bioinformatics pipeline to identify NEPC-specific, overexpressed gene transcripts that encode cell surface proteins. This included the identification of known NEPC surface protein CEACAM5 as well as other potentially targetable proteins (e.g., HMMR and CESLR3). We further showed that cadherin EGF LAG seven-pass G-type receptor 3 (CELSR3) knockdown results in reduced NEPC tumor cell proliferation and migration <i>in vitro</i>. We provide <i>in vivo</i> data including laser capture microdissection followed by RNA-seq data supporting a causal role of CELSR3 in the development and/or maintenance of the phenotype associated with NEPC. Finally, we provide initial data that suggests CELSR3 is a target for T-cell redirection therapeutics. Further work is now needed to fully evaluate the utility of targeting CELSR3 with T-cell redirection or other similar therapeutics as a potential new strategy for patients with NEPC.</p>Significance:<p>The development of effective treatment for patients with NEPC remains an unmet clinical need. We have identified specific surface proteins, including CELSR3, that may serve as novel biomarkers or therapeutic targets for NEPC.</p></div>