Drug resistance presents a challenge to the treatment of cancer patients. Many studies have focused on cell-autonomous mechanisms of drug resistance. By contrast, we proposed that the tumour micro-environment confers innate resistance to therapy. Here we developed a co-culture system to systematically assay the ability of 23 stromal cell types to influence the innate resistance of 45 cancer cell lines to 35 anticancer drugs. We found that stroma-mediated resistance is common, particularly to targeted agents. We characterized further the stroma-mediated resistance of BRAF-mutant melanoma to RAF inhibitors because most patients with this type of cancer show some degree of innate resistance. Proteomic analysis showed that stromal cell secretion of hepatocyte growth factor (HGF) resulted in activation of the HGF receptor MET, reactivation of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-OH kinase (PI(3)K)-AKT signalling pathways, and immediate resistance to RAF inhibition. Immunohistochemistry experiments confirmed stromal cell expression of HGF in patients with BRAF-mutant melanoma and showed a significant correlation between HGF expression by stromal cells and innate resistance to RAF inhibitor treatment. Dual inhibition of RAF and either HGF or MET resulted in reversal of drug resistance, suggesting RAF plus HGF or MET inhibitory combination therapy as a potential therapeutic strategy for BRAF-mutant melanoma. A similar resistance mechanism was uncovered in a subset of BRAF-mutant colorectal and glioblastoma cell lines. More generally, this study indicates that the systematic dissection of interactions between tumours and their micro-environment can uncover important mechanisms underlying drug resistance.

/pdf/tumour-micro-environment-elicits-innate-resistance-to-raf-4nh030q57j.pdf

Tumour micro-environment elicits innate resistance to RAF inhibitors through HGF secretion

Over the past decade, whole genome sequencing and other 'omics' technologies have defined pathogenic driver mutations to which tumor cells are addicted. Such addictions, synthetic lethalities and other tumor vulnerabilities have yielded novel targets for a new generation of cancer drugs to treat discrete, genetically defined patient subgroups. This personalized cancer medicine strategy could eventually replace the conventional one-size-fits-all cytotoxic chemotherapy approach. However, the extraordinary intratumor genetic heterogeneity in cancers revealed by deep sequencing explains why de novo and acquired resistance arise with molecularly targeted drugs and cytotoxic chemotherapy, limiting their utility. One solution to the enduring challenge of polygenic cancer drug resistance is rational combinatorial targeted therapy.

/pdf/combinatorial-drug-therapy-for-cancer-in-the-post-genomic-1zc101i0z5.pdf

Combinatorial drug therapy for cancer in the post-genomic era

Avoidance of apoptosis is critical for the development and sustained growth of tumours. The pro-survival protein myeloid cell leukemia 1 (MCL1) is overexpressed in many cancers, but the development of small molecules targeting this protein that are amenable for clinical testing has been challenging. Here we describe S63845, a small molecule that specifically binds with high affinity to the BH3-binding groove of MCL1. Our mechanistic studies demonstrate that S63845 potently kills MCL1-dependent cancer cells, including multiple myeloma, leukaemia and lymphoma cells, by activating the BAX/BAK-dependent mitochondrial apoptotic pathway. In vivo, S63845 shows potent anti-tumour activity with an acceptable safety margin as a single agent in several cancers. Moreover, MCL1 inhibition, either alone or in combination with other anti-cancer drugs, proved effective against several solid cancer-derived cell lines. These results point towards MCL1 as a target for the treatment of a wide range of tumours.

The MCL1 inhibitor S63845 is tolerable and effective in diverse cancer models

Latent bone metastasis in breast cancer tied to Src-dependent survival signals.

https://gnusha.org/~nmz787/1-s2.0-S0092867412014110-main__UMB.pdf

β-Catenin-Driven Cancers Require a YAP1 Transcriptional Complex for Survival and Tumorigenesis

The aberrant activation of tyrosine kinases represents an important oncogenic mechanism, and yet the majority of such events remain undiscovered. Here we describe a bead-based method for detecting phosphorylation of both wild-type and mutant tyrosine kinases in a multiplexed, high-throughput and low-cost manner. With the aim of establishing a tyrosine kinase-activation catalog, we used this method to profile 130 human cancer lines. Follow-up experiments on the finding that SRC is frequently phosphorylated in glioblastoma cell lines showed that SRC is also activated in primary glioblastoma patient samples and that the SRC inhibitor dasatinib (Sprycel) inhibits viability and cell migration in vitro and tumor growth in vivo. Testing of dasatinib-resistant tyrosine kinase alleles confirmed that SRC is indeed the relevant target of dasatinib, which inhibits many tyrosine kinases. These studies establish the feasibility of tyrosine kinome-wide phosphorylation profiling and point to SRC as a possible therapeutic target in glioblastoma.

Bead-based profiling of tyrosine kinase phosphorylation identifies SRC as a potential target for glioblastoma therapy.

Chemical Genomics Identifies Small-Molecule MCL1 Repressors and BCL-xL as a Predictor of MCL1 Dependency

The Cys-Cys chemokine receptor 6 (CCR6) is a well-established modulator of inflammation Although several genetic associations have been identified between CCR6 polymorphisms and immune system disorders (eg, rheumatoid arthritis and Crohn’s disease), the pharmacological effects of naturally occurring missense mutations in this receptor have yet to be characterized In this study, we initially assessed G protein–mediated signaling and observed that wild-type (WT) CCR6 exhibited ligand-independent activity In addition, we found that the five most frequent CCR6 missense variants (A89T, A150V, R155W, G345S, and A369V) exhibited decreased basal and/or ligand induced Gαi protein signaling To complement the study of these loss-of-function variants, we engineered a set of constitutively active CCR6 receptors Selected mutations enhanced basal G protein–mediated signaling up to 3-fold relative to the WT value Using a bioluminescence resonance energy transfer assay we investigated the ability of each naturally occurring and engineered CCR6 receptor mutant to recruit β-arrestin In contrast to G protein–mediated signaling, β-arrestin mobilization was largely unperturbed by the naturally occurring loss-of-function CCR6 variants Elevated recruitment of β-arrestin was observed in one of the engineered constitutively active mutants (T98P) Our results demonstrate that point mutations in CCR6 can result in either a gain or loss of receptor function These observations underscore the need to explore how CCR6 natural variants may influence immune cell physiology and human disease

https://jpet.aspetjournals.org/content/jpet/360/1/106.full.pdf

Bina Julian

Papers

Bead-based profiling of tyrosine kinase phosphorylation identifies SRC as a potential target for glioblastoma therapy.

Chemical Genomics Identifies Small-Molecule MCL1 Repressors and BCL-xL as a Predictor of MCL1 Dependency

Mutation-Induced Functional Alterations of CCR6.