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Purpose: In ALK-rearranged non–small cell lung cancer (NSCLC), impacts of concomitant genetic alterations on targeted therapies with ALK-tyrosine kinase inhibitors (ALK-TKI) are not yet well understood. Here, we investigated genetic alterations related to ALK-TKI resistance using clinico-genomic data and explored effective therapies to overcome the resistance in preclinical models through the identification of underlying molecular mechanisms. Experimental Design: We used integrated clinical and next-generation sequencing data generated in a nationwide lung cancer genome screening project (LC-SCRUM-Japan). ALK-rearranged NSCLC cell lines expressing wild-type or mutant TP53 were used to evaluate cellular apoptosis induced by ALK-TKIs. Results: In 90 patients with ALK-rearranged NSCLC who were treated with a selective ALK-TKI, alectinib, TP53 comutated patients showed significantly worse progression-free survival (PFS) than TP53 wild-type patients [median PFS, 11.7 months (95% confidence interval, CI, 6.3–not reached, NR) vs. NR (23.6–NR); P = 0.0008; HR, 0.33 (95% CI, 0.17–0.65)]. ALK-rearranged NSCLC cell lines that lost p53 function were resistant to alectinib-induced apoptosis, but a proteasome inhibitior, ixazomib, markedly induced apoptosis in the alectinib-treated cells by increasing the expression of a proapoptotic protein, Noxa, which bound to an antiapoptotic protein, Mcl-1. In subcutaneous tumor models, combination of ixazomib and alectinib prominently induced tumor regression and apoptosis even though the tumors were generated from ALK-rearranged NSCLC cells with nonfunctional p53. Conclusions: These clinical and preclinical results indicate concomitant TP53 mutations reduce the efficacy of alectinib for ALK-rearranged NSCLC and the combined use of a proteasome inhibitor with alectinib is a promising therapy for ALK-rearranged/TP53-mutated NSCLC.

Purpose:Currently, an optimal therapeutic strategy comprising molecularly targeted agents for treating EGFR-mutated non–small cell lung cancer (NSCLC) patients with acquired resistance to osimertinib is not available. Therefore, the initial therapeutic intervention is crucial for the prolonged survival of these patients. The activation of anexelekto (AXL) signaling is known to be associated with intrinsic and acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs). In this study, we investigated the best therapeutic strategy to combat AXL-induced tolerance to EGFR-TKIs using the novel AXL inhibitor ONO-7475.Experimental Design:We examined the efficacy of ONO-7475 in combination with EGFR-TKIs in EGFR-mutated NSCLC cells using in vitro and in vivo experiments. We investigated the correlation between AXL expression in tumors and clinical outcomes with osimertinib for EGFR-mutated NSCLC patients with acquired resistance to initial EGFR-TKIs.Results:ONO-7475 sensitized AXL-overexpressing EGFR-mutant NSCLC cells to the EGFR-TKIs osimertinib and dacomitinib. In addition, ONO-7475 suppressed the emergence and maintenance of EGFR-TKI–tolerant cells. In the cell line–derived xenograft models of AXL-overexpressing EGFR-mutated lung cancer treated with osimertinib, initial combination therapy of ONO-7475 and osimertinib markedly regressed tumors and delayed tumor regrowth compared with osimertinib alone or the combination after acquired resistance to osimertinib. AXL expression in EGFR-TKI refractory tumors did not correlate with the sensitivity of osimertinib.Conclusions:These results demonstrate that ONO-7475 suppresses the emergence and maintenance of tolerant cells to the initial EGFR-TKIs, osimertinib or dacomitinib, in AXL-overexpressing EGFR-mutated NSCLC cells, suggesting that ONO-7475 and osimertinib is a highly potent combination for initial treatment.

Purpose: Rearrangement of the neurotrophic tropomyosin receptor kinase 1 (NTRK1) gene, which encodes tyrosine receptor kinase A (TRK-A), occurs in various cancers, including colon cancer. Although entrectinib is effective in the treatment of central nervous system (CNS) metastases that express NTRK1 fusion proteins, acquired resistance inevitably results in recurrence. The CNS is a sanctuary for targeted drugs; however, the mechanism by which CNS metastases become entrectinib-resistant remains elusive and must be clarified to develop better therapeutics. Experimental Design: The entrectinib-resistant cell line KM12SM-ER was developed by continuous treatment with entrectinib in the brain metastasis–mimicking model inoculated with the entrectinib-sensitive human colon cancer cell line KM12SM, which harbors the TPM3-NTRK1 gene fusion. The mechanism of entrectinib resistance in KM12SM-ER cells was examined by next-generation sequencing. Compounds that overcame entrectinib resistance were screened from a library of 122 kinase inhibitors. Results: KM12SM-ER cells, which showed moderate resistance to entrectinib in vitro, had acquired the G667C mutation in NTRK1. The kinase inhibitor foretinib inhibited TRK-A phosphorylation and the viability of KM12SM-ER cells bearing the NTRK1-G667C mutation in vitro. Moreover, foretinib markedly inhibited the progression of entrectinib-refractory KM12SM-ER–derived liver metastases and brain tumors in animal models, predominantly through inhibition of TRK-A phosphorylation. Conclusions: These results suggest that foretinib may be effective in overcoming entrectinib resistance associated with the NTRK1-G667C mutation in NTRK1 fusion–positive tumors in various organs, including the brain, and provide a rationale for clinical trials of foretinib in cancer patients with entrectinib-resistant tumors harboring the NTRK1-G667C mutation, including patients with brain metastases. Clin Cancer Res; 24(10); 2357–69. ©2018 AACR.

Purpose: The BIM deletion polymorphism is associated with apoptosis resistance to EGFR tyrosine kinase inhibitors (EGFR-TKI), such as gefitinib and erlotinib, in non–small cell lung cancer (NSCLC) harboring EGFR mutations. Here, we investigated whether the BIM deletion polymorphism contributes to resistance against osimertinib, a third-generation EGFR-TKI. In addition, we determined the efficacy of a histone deacetylase (HDAC) inhibitor, vorinostat, against this form of resistance and elucidated the underlying mechanism. Experimental Design: We used EGFR-mutated NSCLC cell lines, which were either heterozygous or homozygous for the BIM deletion polymorphism, to evaluate the effect of osimertinib in vitro and in vivo. Protein expression was examined by Western blotting. Alternative splicing of BIM mRNA was analyzed by RT-PCR. Results: EGFR-mutated NSCLC cell lines with the BIM deletion polymorphism exhibited apoptosis resistance to osimertinib in a polymorphism dosage–dependent manner, and this resistance was overcome by combined use with vorinostat. Experiments with homozygous BIM deletion–positive cells revealed that vorinostat affected the alternative splicing of BIM mRNA in the deletion allele, increased the expression of active BIM protein, and thereby induced apoptosis in osimertinib-treated cells. These effects were mediated predominantly by HDAC3 inhibition. In xenograft models, combined use of vorinostat with osimertinib could regress tumors in EGFR-mutated NSCLC cells homozygous for the BIM deletion polymorphism. Moreover, this combination could induce apoptosis even when tumor cells acquired EGFR-T790M mutations. Conclusions: These findings indicate the importance of developing HDAC3-selective inhibitors, and their combined use with osimertinib, for treating EGFR-mutated lung cancers carrying the BIM deletion polymorphism. Clin Cancer Res; 23(12); 3139–49. ©2016 AACR.

Purpose: Cancer cell microenvironments, including host cells, can critically affect cancer cell behaviors, including drug sensitivity. Although crizotinib, a dual tyrosine kinase inhibitor (TKI) of ALK and Met, shows dramatic effect against EML4-ALK lung cancer cells, these cells can acquire resistance to crizotinib by several mechanisms, including ALK amplification and gatekeeper mutation. We determined whether microenvironmental factors trigger ALK inhibitor resistance in EML4-ALK lung cancer cells. Experimental Design: We tested the effects of ligands produced by endothelial cells and fibroblasts, and the cells themselves, on the susceptibility of EML4-ALK lung cancer cell lines to crizotinib and TAE684, a selective ALK inhibitor active against cells with ALK amplification and gatekeeper mutations, both in vitro and in vivo. Results: EML4-ALK lung cancer cells were highly sensitive to ALK inhibitors. EGF receptor (EGFR) ligands, such as EGF, TGF-α, and HB-EGF, activated EGFR and triggered resistance to crizotinib and TAE684 by transducing bypass survival signaling through Erk1/2 and Akt. Hepatocyte growth factor (HGF) activated Met/Gab1 and triggered resistance to TAE684, but not crizotinib, which inhibits Met. Endothelial cells and fibroblasts, which produce the EGFR ligands and HGF, respectively, decreased the sensitivity of EML4-ALK lung cancer cells to crizotinib and TAE684, respectively. EGFR-TKIs resensitized these cells to crizotinib and Met-TKI to TAE684 even in the presence of EGFR ligands and HGF, respectively. Conclusions: Paracrine receptor activation by ligands from the microenvironment may trigger resistance to ALK inhibitors in EML4-ALK lung cancer cells, suggesting that receptor ligands from microenvironment may be additional targets during treatment with ALK inhibitors. Clin Cancer Res; 18(13); 3592–602. ©2012 AACR.

Purpose: Peritoneal carcinomatosis, often associated with malignant ascites, is the most frequent cause of death in patients with advanced gastric cancer. We previously showed that the CXCR4/CXCL12 axis is involved in the development of peritoneal carcinomatosis from gastric cancer. Here, we investigated whether epidermal growth factor receptor (EGFR) ligands are also involved in the development of peritoneal carcinomatosis from gastric cancer. Experimental Design: The functional involvement of expression of the ErbB family of receptors and/or EGFR ligands was examined in CXCR4-expressing human gastric cancer cells and fibroblasts, clinical samples (primary tumors and ascites), and an animal model. Results: High concentration of the EGFR ligands amphiregulin and heparin-binding EGF-like growth factor (HB-EGF), as well as of CXCL12, were present in malignant ascites. Human gastric cancer cell lines and primary gastric tumors, with high potential to generate peritoneal carcinomatosis, expressed high levels of EGFR and CXCR4 mRNA and protein. Both amphiregulin and HB-EGF enhanced the proliferation, migration, and functional CXCR4 expression in highly CXCR4-expressing gastric cancer NUGC4 cells. Amphiregulin strongly enhanced the proliferation of NUGC4 cells, whereas HB-EGF markedly induced the migration of fibroblasts. Moreover, HB-EGF and CXCL12 together enhanced TNFα-converting enzyme (TACE)-dependent amphiregulin shedding from NUGC4 cells. In an experimental peritoneal carcinomatosis model in mice, cetuximab effectively reduced tumor growth and ascites formation. Conclusions: Our results strongly suggest that the EGFR ligands amphiregulin and HB-EGF play an important role, interacting with the CXCL12/CXCR4 axis, in the development of peritoneal carcinomatosis from gastric cancer, indicating that these two axes may be potential therapeutic targets for peritoneal carcinomatosis of gastric carcinoma. Clin Cancer Res; 17(11); 3619–30. ©2011 AACR.

Preclinical tumor models that resemble the characteristics of patients’ tumors are essential for development of novel therapy. Patient-derived tumor xenograft (PDX) models are considered to be interesting candidates. However, success rate of PDX models of lung cancer, especially adenocarcinoma, is much lower than that of other types of tumors, including colon cancer. This study was conducted to establish clinically relevant PDX models of lung cancer. We obtained fresh surgically resected specimens from 20 NSCLC patients (10 squamous cell carcinomas, 9 adenocarcinomas, and 1 large cell carcinoma) who had submitted the written informed consent for this study, which was performed in accordance with protocols approved by the IRB of Kanazawa University. We inoculated the tumor fragments subcutaneously into immunodeficient mice, NOG mice or SCID hairless outbred (SHO) mice. The tumor take rate was 40% (8/20), with higher rates for squamous cell carcinoma (60%, 6/10) than for adenocarcinoma (22%, 2/9). Interestingly, both of two adenocarcinomas that successfully developed PDX tumors had EGFR mutations, L858R and exon 19 deletion, respectively. These PDX tumors maintained histology of adenocarcinoma and EGFR mutation even after repeated in vivo passages. Furthermore, the third-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) osimertinib dramatically regressed tumors in these EGFR mutated PDX models. Osimertinib treatment is ongoing in these EGFR-mutated PDX models to obtain tumors that acquired resistance to osimertinib. Our PDX models of lung adenocarcinoma with different EGFR mutations may be useful for investigating the mechanisms of resistance to EGFR-TKIs, including third-generation inhibitor osimertinib. Citation Format: Kenji Kita, Koji Fukuda, Akihiro Nishiyama, Sachiko Arai, Shinji Takeuchi, Koushiro Ohtsubo, Kaname Yamashita, Masaya Tamura, Isao Matsumoto, Seiji Yano. Establishment of patient-derived xenograft models of lung adenocarcinoma with two different EGFR mutations, L858R and exon19 deletion [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr A36.

ALK rearrangement, most commonly EML4-ALK, is detected in approximately 3–5% of non-small cell lung cancer (NSCLC). While ALK tyrosine kinase inhibitor (TKI) shows dramatic clinical efficacy in ALK-rearranged NSCLC patients, almost all patients acquire resistance over time. ALK-secondary mutations, including ALK L1196M, are detected in ~40% of ALK-rearranged lung cancers resistant to ALK inhibitors. Epithelial–mesenchymal transition (EMT) was also reported to be associated with various targeted drugs; however, its involvement in ALK-inhibitor resistance is largely unknown. In this study, we continuously gave crizotinib treatment to SCID mice inoculated with EML4-ALK lung cancer cell line A925LPE into thoracic cavity and established crizotinib-resistant cells. We also obtained several single-cell clones with acquired EMT phenotypes (low E-cadherin, high vimentin and ZEB1). MicroRNA profile analysis revealed that EMT was induced by reducing the expression of miR-200 family members, including miR-200c and miR-141, which resulted in increasing ZEB1 and decreasing E-cadherin expression in the clone cells. A reporter assay on a 200-kinase inhibitor library indicated that the histone deacetylase (HDAC) inhibitor, quisinostat, had the highest potential to increase miR-200c-141 promoter activity. Interestingly, pretreatment of the cells with quisinostat reduced ZEB1 expression, increased E-cadherin expression, and thus restored sensitivity to crizotinib and alectinib, mediated by enhanced expression of miR-200c in vitro and in vivo. These results indicate that quisinostat induces mesenchymal-epithelial transition (MET) by upregulating miR-200c expression that targets ZEB1 and thereby resensitizes to ALK-TKI. Furthermore, we analyzed tumor tissue obtained at autopsy from an ALK-rearranged NSCLC patient who acquired resistance to crizotinib. In specimens from the primary lung tumor, as well as from the brain and subcutaneous metastases, both ALK L1196M mutation and EMT were concomitantly detected in all crizotinib-resistant lesions. Therefore, we performed laser capture microdissection and measured the copy number of ALK L1196M in epithelial and mesenchymal type tumor lesions separately. Very interestingly, ALK L1196M mutation was predominantly detected in epithelial type tumor cell lesion; by sharp contrast, it was hardly detected in the mesenchymal type tumor cell lesion. These results clearly demonstrate that EMT is a clinically relevant independent mechanism for crizotinib resistance underlying ALK inhibitor-resistant cancers. Together, our study demonstrates the intratumor heterogeneity constituted by coexistence of resistance mutations and EMT in crizotinib-resistant tumors. HDAC inhibitor pretreatment, which reverts EMT, followed by a new-generation ALK inhibitor may be useful to circumvent resistance due to such intratumor heterogeneity. Citation Format: Koji Fukuda, Shinji Takeuchi, Sachiko Arai, Ryohei Katayama, Shigeki Nanjo, Azusa Tanimoto, Akihiro Nisiyama, Takeshi Suzuki, Kengo Takeuchi, Makoto Nishio, Seiji Yano. Heterogeneity of epithelial-to-mesenchymal transition and resistance mutation in ALK inhibitor-resistant lung cancer and its circumvention [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr B02.

Leptomeningeal carcinomatosis occurs frequently in EGFR-mutant lung cancer, and develops acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs). This study aimed to clarify the mechanism of EGFR-TKI resistance in leptomeningeal carcinomatosis and seek a novel therapeutic strategy. We examined EGFR mutations, including the T790M gatekeeper mutation, in 32 re-biopsy specimens from 12 leptomeningeal carcinomatosis and 20 extracranial lesions of EGFR-mutant lung cancer patients who became refractory to EGFR-TKI treatment. All 32 specimens had the same baseline EGFR mutations, but the T790M mutation was less frequent in leptomeningeal carcinomatosis specimens than in extracranial specimens (8% vs. 55%, P < 0.01). To study molecular mechanisms of acquired EGFR-TKI resistance in leptomeningeal carcinomatosis, we utilized our previously developed mouse model of leptomeningeal carcinomatosis with the EGFR-mutant lung cancer cell line PC-9/ffluc cells, in which acquired resistance to gefitinib was induced by continuous oral treatment. Compared with subcutaneously inoculated gefitinib-resistant tumors, the T790M mutation was less frequent in leptomeningeal carcinomatosis that acquired resistance to gefitinib. PC-9/LMC-GR cells were established from the gefitinib-resistant leptomeningeal carcinomatosis model, and they were found to be intermediately resistant to gefitinib and osimertinib (third-generation EGFR-TKI). Although EGFR-T790M was negative, gefitinib resistance of PC-9/LMC-GR cells was related to MET copy number gain with MET activation. Moreover, combined use of EGFR-TKI and crizotinib, a MET inhibitor, dramatically regressed leptomeningeal carcinomatosis with acquired resistance to gefitinib or osimertinib. These findings suggest that combination therapy with MET inhibitors may be promising for controlling leptomeningeal carcinomatosis that acquires resistance to EGFR-TKIs. This abstract is also being presented as Poster B29. Citation Format: Shigeki Nanjo, Sachiko Arai, Wei Wang, Akito Hata, Nobuyuki Katakami, Seiji Yano. MET copy number gain is associated with gefitinib resistance in leptomeningeal carcinomatosis of EGFR-mutant lung cancer [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr PR13.

Purpose: The secondary T790M mutation in epidermal growth factor receptor (EGFR) is the most frequent cause of acquired resistance to the reversible EGFR tyrosine kinase inhibitors (EGFR-TKI), gefitinib and erlotinib, in lung cancer. Irreversible EGFR-TKIs are expected to overcome the reversible EGFR-TKI resistance of lung cancer harboring T790M mutation in EGFR. However, it is clear that resistance may also develop to this class of inhibitors. We showed previously that hepatocyte growth factor (HGF) induced gefitinib resistance of lung cancer harboring EGFR-activating mutations. Here, we investigated whether HGF induced resistance to the irreversible EGFR-TKI, CL-387,785, in lung cancer cells (H1975) harboring both L858R activating mutation and T790M secondary mutation in EGFR. Experimental Design: CL-387,785 sensitivity and signal transduction in H1975 cells were examined in the presence or absence of HGF or HGF-producing fibroblasts with or without HGF-MET inhibitors. Results: HGF reduced susceptibility to CL-387,785 in H1975 cells. Western blotting and small interfering RNA analyses indicated that HGF-induced hyposensitivity was mediated by the MET/phosphoinositide 3-kinase/Akt signaling pathway independent of EGFR, ErbB2, ErbB3, and ErbB4. Hyposensitivity of H1975 cells to CL-387,785 was also induced by coculture with high-level HGF-producing lung fibroblasts. The hyposensitivity was abrogated by treatment with anti-HGF neutralizing antibody, HGF antagonist NK4, or MET-TKI. Conclusions: We showed HGF-mediated hyposensitivity as a novel mechanism of resistance to irreversible EGFR-TKIs. It will be clinically valuable to investigate the involvement of HGF-MET–mediated signaling in de novo and acquired resistance to irreversible EGFR-TKIs in lung cancer harboring T790M mutation in EGFR. Clin Cancer Res; 16(1); 174–83

Purpose: Malignant pleural mesothelioma (MPM) is a biologically heterogeneous malignant disease with a poor prognosis. We reported previously that the anti–vascular endothelial growth factor (VEGF) antibody, bevacizumab, effectively inhibited the progression of VEGF-high-producing (but not VEGF-low-producing) MPM cells in orthotopic implantation models, indicating the need for novel therapeutic strategies to improve the poor prognosis of this disease. Therefore, we focused on the multi–tyrosine kinase inhibitor E7080 and assessed its therapeutic efficacy against MPM cells with different proangiogenic cytokine production profiles. Experimental Design: The efficacy of E7080 was assayed in orthotopic implantation of severe combined immunodeficient mouse models with three human MPM cell lines (MSTO-211H, NCI-H290, and Y-MESO-14). Results: With regard to proangiogenic cytokine production profiles, MSTO-211H and Y-MESO-14 cells were MPM cells producing high levels of fibroblast growth factor-2 and VEGF, respectively. NCI-H290 cells produced low levels of fibroblast growth factor-2 and VEGF compared with the other two cell lines. E7080 potently suppressed the phosphorylation of VEGF receptor-2 and FGF receptor 1 and, thus, inhibited proliferation of endothelial cells, but not that of the MPM cell lines, in vitro. Orthotopically inoculated MSTO-211H cells produced only thoracic tumors, whereas NCI-H290 and Y-MESO-14 cells also developed pleural effusions. Treatment with E7080 potently inhibited the progression of these three MPM cell lines and markedly prolonged mouse survival, which was associated with decreased numbers of tumor-associated vessels and proliferating MPM cells in the tumor. Conclusions: These results strongly suggest broad-spectrum activity of E7080 against MPM with different proangiogenic cytokine production profiles in humans. (Clin Cancer Res 2009;15(23):7229–37)

Purpose: Lung cancers with epidermal growth factor receptor (EGFR)–activating mutations show good clinical response to gefitinib and erlotinib, selective tyrosine kinase inhibitors (TKI) to EGFR, but these tumors invariably develop drug resistance. Host stromal cells have been found to have a considerable effect on the behavior of cancer cells. Little is known, however, about the role of host cells on the sensitivity of cancer cells to receptor TKIs. We have therefore assessed the effect of crosstalk between stromal cells and lung cancer cells harboring EGFR mutations on susceptibility to EGFR-TKIs. Experimental Design: We evaluated the gefitinib sensitivity of lung cancer cells with EGFR-activating mutations, PC-9 and HCC827, when cocultured with fibroblasts and coinjected into severe combined immunodeficient mice. We also examined the effect of lung cancer cells to fibroblast recruitment. Results: Both human fibroblast cell lines and primary cultured fibroblasts produced various levels of hepatocyte growth factor (HGF). Lung cancer cells markedly recruited fibroblasts. The lung cancer cells became resistant to EGFR-TKIs when cocultured in vitro with HGF-producing fibroblasts and coinjected into severe combined immunodeficient mice. Importantly, combined use of gefitinib plus anti-HGF antibody or the HGF antagonist, NK4, successfully overcame the fibroblast-induced EGFR-TKI resistance both in vitro and in vivo. Colocalization of fibroblasts and HGF was detected in both xenograft tumors in mouse model and lung cancer patient specimens. Conclusions: These findings indicate that crosstalk to stromal fibroblasts plays a critical role in lung cancer resistance to EGFR-TKIs and may be an ideal therapeutic target in lung cancer with EGFR-activating mutations. (Clin Cancer Res 2009;15(21):6630–8)

Purpose: Malignant pleural mesothelioma (MPM) is an aggressive malignancy, which has a poor prognosis with a median survival of less than 1 year. The vascular endothelial growth factor (VEGF) has been reported to be an ideal therapeutic target, and a multitargeted antifolate, pemetrexed, has been clinically used for the treatment of MPM. Experimental Design: We examined the therapeutic efficacy of the antihuman VEGF neutralizing antibody, bevacizumab, in combination with pemetrexed against two different human MPM cells, EHMES-10 and MSTO-211H, orthotopically inoculated into severe combined immunodeficient mice. Results: Bevacizumab inhibited a VEGF-induced proliferation of the human endothelial cells in a dose-dependent manner, but it had no effect on the proliferation of the two MPM cell lines in vitro. The orthotopically inoculated EHMES-10 cells (VEGF high expressing) produced thoracic tumors and a large volume of bloody pleural effusion, whereas the MSTO-211H cells (VEGF low expressing) produced thoracic tumors and a small volume of bloody effusions. Treatment with bevacizumab effectively inhibited the production of thoracic tumors and dramatically prevented the production of pleural effusion by the EHMES-10 cells but not the MSTO-211H cells. Treatment with bevacizumab reduced the number of enlarged tumor-associated vessels and proliferating tumor cells. Moreover, treatment with bevacizumab in combination with pemetrexed more effectively suppressed the formation of the pleural effusion and prolonged the survival compared with the control and monotherapy in the EHMES-10 cell–bearing severe combined immunodeficient mice. Conclusions: These results suggest that the combined use of bevacizumab and pemetrexed may therefore be promising for controlling the progression of MPM highly expressing VEGF.

Purpose: The purpose of this study was to determine therapeutic effect of a novel antibiotic, reveromycin A, against osteolytic bone metastasis of human small cell lung cancer (SBC-5) cells. Results: Reveromycin A induced apoptosis specifically in osteoclasts in vitro. Although reveromycin A did not inhibit SBC-5 cell proliferation, it suppressed the expression of parathyroid hormone–related peptide. Intravenous inoculation of SBC-5 cells in natural killer cell–depleted severe combined immunodeficient mice produced experimental metastases in multiple organs, including the bone. Daily administration of reveromycin A inhibited the bone metastasis, but not visceral metastasis, in a dose-dependent manner. Histologic analyses revealed that although treatment with reveromycin A did not affect the number of proliferating tumor cells, it decreased the number of osteoclasts and increased apoptotic cells in bone lesions. Conclusions: These findings suggest that reveromycin A may inhibit osteolytic bone metastasis through suppression of osteoclast activity by directly inducing apoptosis and indirectly inhibiting tumor cell–derived parathyroid hormone–related peptide production. Therefore, reveromycin A may be a novel, potent therapeutic agent against osteolytic bone metastasis of lung cancer in humans.

Background: Small-cell lung cancer is often characterized by rapid growth and metastatic spread. Because tumor growth and metastasis are angiogenesis dependent, there is great interest in therapeutic strategies that aim to inhibit tumor angiogenesis. Methods: The effect of ZD6474, an orally available inhibitor of vascular endothelial growth factor receptor-2 (VEGFR-2) and epidermal growth factor tyrosine kinases, was studied in experimental multiple-organ metastasis models with human small-cell lung cancer cell lines (SBC-3 or SBC-5) in natural killer cell–depleted severe combined immunodeficient mice. Results: Intravenously inoculated SBC-5 cells produced experimental metastases in the liver, lung, and bone whereas SBC-3 cells produced the metastases in the liver, systemic lymph nodes, and kidneys. Daily oral treatment with ZD6474 (50 mg/kg), started on day 14 (after the establishment of micrometastases), significantly reduced the frequency of large (>3 mm) metastatic colonies (in the liver and lymph nodes) and osteolytic bone lesions. ZD6474 treatment did not significantly reduce the frequency of small ( Conclusions: These results suggest that ZD6474 may be of potential therapeutic value in inhibiting the growth of metastatic small-cell lung cancer in humans. Phase II trials with ZD6474 are currently ongoing in a range of solid tumors.

Cancer cell microenvironments, including host cells, can critically affect cancer cell behaviors, including drug sensitivity. We recently reported that hepatocyte growth factor (HGF), the ligand of a tyrosine kinase receptor Met, can be produced not only by cancer cells but also host fibroblasts, activates Met and the downstream PI3K/Akt pathway and triggers resistance to EGFR inhibitors in EGFR mutant lung cancer cells (Yano S et al, Cancer Res, 2008). Crizotinib, a dual inhibitor of ALK and Met, shows dramatic effects against EML4-ALK lung cancer cells, but these cells can acquire resistance by several mechanisms, including ALK amplification and gatekeeper mutation. Although elective ALK inhibitors can overcome crizotinib resistance due to these mechanisms, these cells may become resistant to these inhibitors. Here, we determined whether microenvironmental factors trigger ALK inhibitor resistance in EML4-ALK lung cancer cells. We tested the effects of ligands produced by endothelial cells and fibroblasts, and the cells themselves, on the susceptibility of EML4-ALK lung cancer cell lines to crizotinib and TAE684, a selective ALK inhibitor active against cells with ALK amplification and gatekeeper mutations, both in vitro and in vivo. EML4-ALK lung cancer cells were highly sensitive to ALK inhibitors. EGFR ligands, such as EGF, TGF-α, and HB-EGF, activated EGFR and triggered resistance to crizotinib and TAE684 by transducing bypass survival signaling through Erk1/2 and Akt. HGF activated Met/Gab1 and triggered resistance to TAE684, but not crizotinib, which inhibits Met. Endothelial cells and fibroblasts, which produce the EGFR ligands and HGF, respectively, decreased the sensitivity of EML4-ALK lung cancer cells to crizotinib and TAE684, respectively. EGFR-TKIs re-sensitized these cells to crizotinib and Met-TKI to TAE684 even in the presence of EGFR ligands and HGF, respectively. Our findings suggest that paracrine receptor activation by ligands from the microenvironment may trigger resistance to ALK inhibitors in EML4-ALK lung cancer cells, and provide a rationale for targeting receptor ligands in the microenvironment for more successful treatment with ALK inhibitors. These observation further raise clinical questions which classes ALK inhibitors are more beneficial for EML4-ALK lung cancer patients. This proffered talk is also presented as Poster A30.