Not just gRASping at flaws: Finding vulnerabilities to develop novel therapies for treating KRAS mutant cancers

がん進展制御研究所Mutations in Kirsten rat-sarcoma (KRAS) are well appreciated to be major drivers of human cancers through dysregulation of multiple growth and survival pathways. Similar to many other non-kinase oncogenes and tumor suppressors, efforts to directly target KRAS pharmaceutically have not yet materialized. As a result, there is broad interest in an alternative approach to develop therapies that induce synthetic lethality in cancers with mutant KRAS, therefore exposing the particular vulnerabilities of these cancers. Fueling these efforts is our increased understanding into the biology driving KRAS mutant cancers, in particular the important pathways that mutant KRAS governs to promote survival. In this mini-review, we summarize the latest approaches to treat KRAS mutant cancers and the rationale behind them. © 2014 The Authors

Receptor ligand-triggered resistance to alectinib and its circumvention by Hsp90 inhibition in EML4-ALK lung cancer cells

Alectinib is a new generation ALK inhibitor with activity against the gatekeeper L1196M mutation that showed remarkable activity in a phase I/II study with echinoderm microtubule associated protein-like 4 (EML4) - anaplastic lymphoma kinase (ALK) non-small cell lung cancer (NSCLC) patients. However, alectinib resistance may eventually develop. Here, we found that EGFR ligands and HGF, a ligand of the MET receptor, activate EGFR and MET, respectively, as alternative pathways, and thereby induce resistance to alectinib. Additionally, the heat shock protein 90 (Hsp90) inhibitor suppressed protein expression of ALK, MET, EGFR, and AKT, and thereby induced apoptosis in EML4-ALK NSCLC cells, even in the presence of EGFR ligands or HGF. These results suggest that Hsp90 inhibitors may overcome ligand-triggered resistance to new generation ALK inhibitors and may result in more successful treatment of NSCLC patients with EML4-ALK

High efficacy of third generation EGFR inhibitor AZD9291 in a leptomeningeal carcinomatosis model with EGFR-mutant lung cancer cells

Leptomeningeal carcinomatosis (LMC) remarkably decreases the quality of life of EGFR-mutant lung cancer patients. In contrast to the lesions outside the central nervous system (CNS), molecular mechanisms of EGFR tyrosine kinase inhibitor (TKI) resistance in CNS lesions including LMC are largely unknown. In this study, we established an in vivo imaging model for LMC with EGFR mutant lung cancer cell lines harboring an exon 19 deletion in EGFR and evaluated the effect of first generation EGFR-TKIs, erlotinib, second generation afatinib, and third generation AZD9291. In PC-9/ffluc model, erlotinib treatment slowed the development of LMC. Importantly, treatment with afatinib or AZD9291 apparently delayed the development of LMC. Moreover, treatment with a higher dose of AZD9291, also associated with inhibited phosphorylation of EGFR downstream molecule S6, regressed LMC refractory to the aforementioned EGFR-TKI treatments. These observations suggest that the third generation EGFR-TKI AZD9291 may be an effective treatment for first or second generation EGFR-TKI resistant LMC caused by EGFR-mutant lung cancer

TGF-β-dependent reprogramming of amino acid metabolism induces epithelial–mesenchymal transition in non-small cell lung cancers

Epithelial–mesenchymal transition (EMT)—a fundamental process in embryogenesis and wound healing—promotes tumor metastasis and resistance to chemotherapy. While studies have identified signaling components and transcriptional factors responsible in the TGF-β-dependent EMT, whether and how intracellular metabolism is integrated with EMT remains to be fully elucidated. Here, we showed that TGF-β induces reprogramming of intracellular amino acid metabolism, which is necessary to promote EMT in non-small cell lung cancer cells. Combined metabolome and transcriptome analysis identified prolyl 4-hydroxylase α3 (P4HA3), an enzyme implicated in cancer metabolism, to be upregulated during TGF-β stimulation. Further, knockdown of P4HA3 diminished TGF-β-dependent changes in amino acids, EMT, and tumor metastasis. Conversely, manipulation of extracellular amino acids induced EMT-like responses without TGF-β stimulation. These results suggest a previously unappreciated requirement for the reprogramming of amino acid metabolism via P4HA3 for TGF-β-dependent EMT and implicate a P4HA3 inhibitor as a potential therapeutic agent for cancer

Ability of the Met kinase inhibitor crizotinib and new generation EGFR inhibitors to overcome resistance to EGFR inhibitors

Purpose: Although EGF receptor tyrosine kinase inhibitors (EGFR-TKI) have shown dramatic effects against EGFR mutant lung cancer, patients ultimately develop resistance by multiple mechanisms. We therefore assessed the ability of combined treatment with the Met inhibitor crizotinib and new generation EGFR-TKIs to overcome resistance to first-generation EGFR-TKIs. Experimental Design: Lung cancer cell lines made resistant to EGFR-TKIs by the gatekeeper EGFR-T790M mutation, Met amplification, and HGF overexpression and mice with tumors induced by these cells were treated with crizotinib and a new generation EGFR-TKI. Results: The new generation EGFR-TKI inhibited the growth of lung cancer cells containing the gatekeeper EGFRT790M mutation, but did not inhibit the growth of cells with Met amplification or HGF overexpression. In contrast, combined therapy with crizotinib plus afatinib or WZ4002 was effective against all three types of cells, inhibiting EGFR and Met phosphorylation and their downstream molecules. Crizotinib combined with afatinib or WZ4002 potently inhibited the growth of mouse tumors induced by these lung cancer cell lines. However, the combination of high dose crizotinib and afatinib, but not WZ4002, triggered severe adverse events. Conclusions: Our results suggest that the dual blockade of mutant EGFR and Met by crizotinib and a new generation EGFR-TKI may be promising for overcoming resistance to reversible EGFR-TKIs but careful assessment is warranted clinically. © 2013 Nanjo et al

Assessment of ABT-263 activity across a cancer cell line collection leads to a potent combination therapy for small-cell lung cancer

BH3 mimetics such as ABT-263 induce apoptosis in a subset of cancer models. However, these drugs have shown limited clinical efficacy as single agents in small-cell lung cancer (SCLC) and other solid tumor malignancies, and rational combination strategies remain underexplored. To develop a novel therapeutic approach, we examined the efficacy of ABT-263 across >500 cancer cell lines, including 311 for which we had matched expression data for select genes. We found that high expression of the proapoptotic gene Bcl2-interacting mediator of cell death (BIM) predicts sensitivity to ABT-263. In particular, SCLC cell lines possessed greater BIM transcript levels than most other solid tumors and are among the most sensitive to ABT-263. However, a subset of relatively resistant SCLC cell lines has concomitant high expression of the antiapoptotic myeloid cell leukemia 1 (MCL-1). Whereas ABT-263 released BIM from complexes with BCL-2 and BCL-XL, high expression of MCL-1 sequestered BIM released from BCL-2 and BCL-XL, thereby abrogating apoptosis. We found that SCLCs were sensitized to ABT-263 via TORC1/2 inhibition, which led to reduced MCL-1 protein levels, thereby facilitating BIM-mediated apoptosis. AZD8055 and ABT-263 together induced marked apoptosis in vitro, as well as tumor regressions in multiple SCLC xenograft models. In a Tp53; Rb1 deletion genetically engineered mouse model of SCLC, the combination of ABT-263 and AZD8055 significantly repressed tumor growth and induced tumor regressions compared with either drug alone. Furthermore, in a SCLC patient-derived xenograft model that was resistant to ABT-263 alone, the addition of AZD8055 induced potent tumor regression. Therefore, addition of a TORC1/2 inhibitor offers a therapeutic strategy to markedly improve ABT-263 activity in SCLC.United States. Dept. of Defense (Grant W81-XWH-13-1-0323)National Cancer Institute (U.S.) (Cancer Center Support Grant P30-CA14051

A murine lung cancer co-clinical trial identifies genetic modifiers of therapeutic response

Targeted therapies have demonstrated efficacy against specific subsets of molecularly defined cancers1–4. Although most patients with lung cancer are stratified according to a single oncogenic driver, cancers harbouring identical activating genetic mutations show large variations in their responses to the same targeted therapy1,3. The biology underlying this heterogeneity is not well understood, and the impact of co-existing genetic mutations, especially the loss of tumour suppressors5–9, has not been fully explored. Here we use genetically engineered mouse models to conduct a ‘co-clinical’ trial that mirrors an ongoing human clinical trial in patients with KRAS-mutant lung cancers. This trial aims to determine if the MEK inhibitor selumetinib (AZD6244)10 increases the efficacy of docetaxel, a standard of care chemotherapy. Our studies demonstrate that concomitant loss of either p53 (also known as Tp53) or Lkb1 (also known as Stk11), two clinically relevant tumour suppressors6,9,11,12, markedly impaired the response of Kras-mutant cancers to docetaxel monotherapy. We observed that the addition of selumetinib provided substantial benefit for mice with lung cancer caused by Kras and Kras and p53 mutations, but mice with Kras and Lkb1 mutations had primary resistance to this combination therapy. Pharmacodynamic studies, including positron-emission tomography (PET) and computed tomography (CT), identified biological markers in mice and patients that provide a rationale for the differential efficacy of these therapies in the different genotypes. These co-clinical results identify predictive genetic biomarkers that should be validated by interrogating samples from patients enrolled on the concurrent clinical trial. These studies also highlight the rationale for synchronous co-clinical trials, not only to anticipate the results of ongoing human clinical trials, but also to generate clinically relevant hypotheses that can inform the analysis and design of human studies

PI3 KおよびERKパスウエイを標的としたKRAS変異腫瘍に対する新規治療開発 (国際共同研究強化)

愛知県がんセンター / 金沢大学がん進展制御研究所KRAS変異腫瘍が上皮間葉移行状態により2種類に分類できることを明らかにした。ERKパスウエイの抑制は、上流受容体のフィードバック活性化を誘導するが、活性化される受容体が上皮型ではERBB3、間葉型ではFGFR1であり、MEK阻害薬と受容体阻害薬の併用が、それぞれの性質を示す腫瘍の治療に有効であること示した。また、上皮間葉移行状態に関わらずMEK阻害薬と併用効果を示す標的としてSHP2を同定した。近年開発の進むKRAS G12C変異直接阻害薬について、感受性や耐性規定因子を解析・同定した。さらに本課題を通じ新たな国際共同研究を展開しBRAF遺伝子変異腫瘍に対する個別化治療の提唱を行った。We identified epithelial-to-mesenchymal transition (EMT) rewires the expression of receptor tyrosine kinases (RTKs), leading to differential feedback activation of the ERK pathway following MEK inhibition in KRAS mutant cancer. In epithelial-like cancers, this feedback was attributed to ERBB3-mediated activation of MEK and AKT. In contrast, in mesenchymal-like cancers, FGFR1 was dominantly expressed but suppressed by the negative regulator Sprouty proteins; MEK inhibition led to repression of SPRY4 and subsequent FGFR1-mediated reactivation of MEK and AKT. Therapeutically, the combination of a MEK inhibitor with respective RTK inhibitors induced cell death in vitro and tumor regressions in vivo. We also functionally characterized BRAF mutant cancers by an international collaboration. Collectively, we have established the rationale and a therapeutic approach to treat KRAS-mutant lung cancers based on EMT status, and BRAF mutant cancers based on its functional classification.研究課題/領域番号:15KK0303, 研究期間(年度):2016-2018出典：「PI3 KおよびERKパスウエイを標的としたKRAS変異腫瘍に対する新規治療開発 (国際共同研究強化)」研究成果報告書　課題番号15KK0303（KAKEN：科学研究費助成事業データベース（国立情報学研究所））（https://kaken.nii.ac.jp/report/KAKENHI-PROJECT-15KK0303/15KK0303seika/)を加工して作