Kadoaki Ohashi

Non–Small Cell Lung Cancer Cells Acquire Resistance to the ALK Inhibitor Alectinib by Activating Alternative Receptor Tyrosine Kinases

Crizotinib is the standard of care for advanced non-small cell lung cancer (NSCLC) patients harboring the anaplastic lymphoma kinase (ALK) fusion gene, but resistance invariably develops. Unlike crizotinib, alectinib is a selective ALK tyrosine kinase inhibitor (TKI) with more potent antitumor effects and a favorable toxicity profile, even in crizotinib-resistant cases. However, acquired resistance to alectinib, as for other TKIs, remains a limitation of its efficacy. Therefore, we investigated the mechanisms by which human NSCLC cells acquire resistance to alectinib. We established two alectinib-resistant cell lines that did not harbor the secondary ALK mutations frequently occurring in crizotinib-resistant cells. One cell line lost the EML4-ALK fusion gene, but exhibited increased activation of insulin-like growth factor-1 receptor (IGF1R) and human epidermal growth factor receptor 3 (HER3), and overexpressed the HER3 ligand neuregulin 1. Accordingly, pharmacologic inhibition of IGF1R and HER3 signaling overcame resistance to alectinib in this cell line. The second alectinib-resistant cell line displayed stimulated HGF autocrine signaling that promoted MET activation and remained sensitive to crizotinib treatment. Taken together, our findings reveal two novel mechanisms underlying alectinib resistance that are caused by the activation of alternative tyrosine kinase receptors rather than by secondary ALK mutations. These studies may guide the development of comprehensive treatment strategies that take into consideration the various approaches ALK-positive lung tumors use to withstand therapeutic insult.

JAK2-related pathway induces acquired erlotinib resistance in lung cancer cells harboring an epidermal growth factor receptor-activating mutation

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, such as gefitinib and erlotinib, are effective for non‐small cell lung cancer with activating EGFR mutations. However, even in patients with an initial dramatic response to such a drug, acquired resistance develops after 6–12 months. A secondary mutation of T790M in EGFR and amplification of the MET gene account for this resistance; however, the mechanism(s) of approximately 30% of acquired resistance cases remain unknown. We established an erlotinib‐resistant lung cancer cell line named PC‐9/ER3 that harbors an EGFR mutation after continuously exposing PC‐9 cells to erlotinib. PC‐9/ER3 cells were 136‐fold more resistant to erlotinib than the parental cells. Although the PC‐9/ER3 cells did not carry the T790M mutation or MET amplification and had similar levels of phosphorylated (p) STAT3, pJAK2 increased in the resistant cells. It was found in the present study that 3–12 h of exposure to erlotinib in both cell lines did not affect pJAK2 expression, but did result in increased pSTAT3 expression. pAkt in PC‐9/ER3 cells was less suppressed than in PC‐9 cells, although pEGFR and pMAPK were markedly suppressed in both cell lines. The combined treatment of erlotinib plus a JAK2 inhibitor (JSI‐124) suppressed pAkt in PC‐9/ER3 cells. Similarly, the combination of erlotinib plus JSI‐124 or siRNA against JAK2 restored sensitivity to erlotinib in PC‐9/ER3 cells. The combination of erlotinib plus JSI‐124 was also effective for reducing PC‐9/ER3 tumors in a murine xenograft model. Our results suggest that the activation of JAK2 partially accounts for acquired erlotinib resistance.(Cancer Sci, doi: 10.1111/j.1349‐7006.2012.02363.x, 2012)

STAT3 expression in activating EGFR-driven adenocarcinoma of the lung.

Bronchioloalveolar carcinoma (BAC) pattern is often seen at the margin of invasive adenocarcinomas. We investigated EGFR signaling abnormalities involved in the progression of adenocarcinoma. Fifty tumors were obtained from patients who underwent surgery for lung adenocarcinoma seen as dense areas in ground glass opacity on computed tomography. Six, 18, and 26 tumors <1cm, 1-2 cm, and ≥2 cm in diameter, respectively, were analyzed. Of the 24 tumors ≤2 cm in diameter, nine were preinvasive and 15 were invasive. EGFR, pAKT, and pMAPK were overexpressed in the center of the adenocarcinoma compared to the BAC component (p<0.01) by immunohistochemistry, while pSTAT3 expression was reversed (p=0.017). In the tumors ≤2 cm in diameter, pSTAT3 expression in the central area was higher in preinvasive tumors than in invasive tumors (p=0.005). pSTAT3 was identified in the BAC component of 88% of the EGFR mutant (n=17) and 82% of the wild-type tumors (n=33). Transgenic mice expressing delE748-A752 EGFR and two lung cancer cell lines (PC-9 mutant and A549 wild-type EGFR) were also investigated. In transgenic mice, pSTAT3 was overexpressed in the BAC component around the adenocarcinoma center. Two lung cancer cell lines that overexpressed pSTAT3 were equally sensitive to a JAK2/STAT3 inhibitor (JSI-124). The role of STAT3 in the progression of adenocarcinoma should be further pursued.

Vandetanib is effective in EGFR-mutant lung cancer cells with PTEN deficiency.

The effectiveness of vandetanib, an agent that targets RET, VEGFR and EGFR signaling, against EGFR-mutant lung cancer cells with PTEN loss was investigated. Two EGFR mutant non-small cell lung cancer (NSCLC) cell lines, PC-9 (PTEN wild type) and NCI-H1650 (PTEN null), were used. We transfected an intact PTEN gene into H1650 cells and knocked down PTEN expression in PC-9 cells using shRNA. The effectiveness of gefitinib and vandetanib was assessed using a xenograft model. While PC-9 cells were more resistant to vandetanib than gefitinib, H1650 cells were more sensitive to vandetanib than gefitinib. Both gefitinib and vandetanib suppressed the activation of EGFR and MAPK in H1650 cells, although phosphorylated AKT levels were not affected. In an H1650 cell xenograft model, vandetanib was also more effective than gefitinib. Although PTEN-transfected H1650 cells did not show restoration of sensitivity to gefitinib in vitro, the xenograft tumors responded to gefitinib and vandetanib. Knockdown of PTEN in PC-9 cells caused resistance to gefitinib. In conclusion, vandetanib might be effective in NSCLC with EGFR mutations that lack PTEN expression. The contribution of PTEN absence to vandetanib activity in NSCLC cells harboring EGFR mutations should be further examined.

Induction of lung adenocarcinoma in transgenic mice expressing activated EGFR driven by the SP‐C promoter

To investigate the role of an activating epidermal growth factor receptor (EGFR) mutation in lung cancer, we generated transgenic mice expressing the delE748‐A752 mutant version of mouse EGFR driven by the SP‐C promoter, which is equivalent to the delE746‐A750 mutation found in lung cancer patients. Strikingly, the mice invariably developed multifocal lung adenocarcinomas of varying sizes at between 5 and 6 weeks of age, and they died from tumor progression approximately 2 months later if left untreated. Daily oral administration of the EGFR tyrosine kinase inhibitor (TKI) gefitinib (5 mg/kg/day) reduced the total and phosphorylation levels of EGFR to those in wild‐type mouse lung tissue; in addition, it abrogated tumor growth within 1 week and prolonged survival to >30 weeks. Interestingly, phosphorylated ErbB2, ErbB3, and thyroid transcriptional factor‐1 increased in the transgenic mice compared with those in wild‐type mice. They might play some roles in tumors progression in the transgenic mice. This model will be useful for studying the mechanisms of carcinogenesis, chemoprevention, and acquired resistance to EGFR TKIs in lung cancer patients carrying activating EGFR mutations. (Cancer Sci 2008; 99: 1747–1753)

Magnitude of the Benefit of Progression-Free Survival as a Potential Surrogate Marker in Phase 3 Trials Assessing Targeted Agents in Molecularly Selected Patients with Advanced Non-Small Cell Lung Cancer: Systematic Review

Background In evaluation of the clinical benefit of a new targeted agent in a phase 3 trial enrolling molecularly selected patients with advanced non-small cell lung cancer (NSCLC), overall survival (OS) as an endpoint seems to be of limited use because of a high level of treatment crossover for ethical reasons. A more efficient and useful indicator for assessing efficacy is needed. Methods and Findings We identified 18 phase 3 trials in the literature investigating EGFR-tyrosine kinase inhibitor (TKIs) or ALK-TKIs, now approved for use to treat NSCLC, compared with standard cytotoxic chemotherapy (eight trials were performed in molecularly selected patients and ten using an “all-comer” design). Receiver operating characteristic analysis was used to identify the best threshold by which to divide the groups. Although trials enrolling molecularly selected patients and all-comer trials had similar OS-hazard ratios (OS-HRs) (0.99 vs. 1.04), the former exhibited greater progression-free survival-hazard ratios (PFS-HR) (mean, 0.40 vs. 1.01; P<0.01). A PFS-HR of 0.60 successfully distinguished between the two types of trials (sensitivity 100%, specificity 100%). The odds ratio for overall response was higher in trials with molecularly selected patients than in all-comer trials (mean: 6.10 vs. 1.64; P<0.01). An odds ratio of 3.40 for response afforded a sensitivity of 88% and a specificity of 90%. Conclusion The notably enhanced PFS benefit was quite specific to trials with molecularly selected patients. A PFS-HR cutoff of ∼0.6 may help detect clinical benefit of molecular targeted agents in which OS is of limited use, although desired threshold might differ in an individual trial.

Effect of gefitinib on N-nitrosamine-4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone induced lung tumorigenesis in A/J mice

Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). N-Nitrosamine-4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a potent carcinogen found in tobacco smoke, induces lung tumors in A/J mice. NNK induces cellular transformation resulting in the over-expression of EGFR. Accordingly, EGFR may be a target for cancer prevention. In this study, we investigated the effect of gefitinib on NNK-induced tumorigenesis and the carcinogenicity of gefitinib in A/J mice. A total of 180 four-week-old female A/J mice were randomly divided into six groups: group 1 (controls), treated with deionized water; group 2, treated with 5 mg/kg p.o. gefitinib; group 3, treated with 50 mg/kg p.o. gefitinib (to test the carcinogenicity of gefitinib); group 4 (controls for NNK treatment), treated with deionized water; group 5, treated with 5 mg/kg p.o. gefitinib; and group 6, treated with 50 mg/kg p.o. gefitinib and injected with NNK once at 8 weeks of age to test the chemopreventive activity of gefitinib. Gefitinib was given once a day, 5 days a week by gavage, beginning at 4 weeks of age and continuing for 26 weeks. All mice were sacrificed at 30 weeks of age. The multiplicities of the NNK-induced lung tumors were significantly suppressed in a dose-dependent manner. Gefitinib had no effect on body weight at a low dose. The administration of gefitinib alone for 26 weeks did not induce tumorigenesis; instead, it significantly suppressed the incidence of spontaneous tumors in the mice, in contrast with other anti-cancer agents. Gefitinib did not induce lung fibrosis when compared with control mice by Azan-Mallory staining. Our results suggest that gefitinib has a weak but significant chemopreventive effect with no carcinogenicity or pulmonary toxicity in A/J mice.

A Phase II Study of Trastuzumab Emtansine in HER2-Positive Non–Small Cell Lung Cancer

&NA; Trastuzumab emtansine (T‐DM1), an anti–erb‐b2 receptor tyrosine kinase 2 (HER2) antibody‐drug conjugate, has been shown to significantly improve survival in HER2‐positive breast cancer. We report a phase II trial of T‐DM1 monotherapy in relapsed NSCLC with documented HER2 positivity (an immunohistochemistry [IHC] score of 3+, both an IHC score of 2+ and fluorescence in situ hybridization positivity, or exon 20 mutation). This study was terminated early because of limited efficacy. The demographic characteristics in the 15 assessable patients were as follows: median age, 67 years; male sex, 47%; performance status of 0 to 1, 80%; HER2 status IHC 3+, 33%; HER status IHC 2+/fluorescence in situ hybridization–positive, 20%; and exon 20 mutation, 47%. The median number of delivered cycles was 3 (range 1–11). One patient achieved a partial response with an objective response rate of 6.7% (90% confidence interval: 0.2–32.0). With a median follow‐up time of 9.2 months, the median progression‐free survival time and median survival time were 2.0 and 10.9 months, respectively. Grade 3 or 4 adverse events included thrombocytopenia (40%) and hepatotoxicity (20%) without any treatment‐related deaths. T‐DM1 had a limited efficacy for HER2‐positive NSCLC in our cohort. Applying the concept of precision medicine to tumors appears challenging; thus, additional molecular approaches are warranted.

Trastuzumab Emtansine in HER2+ Recurrent Metastatic Non–Small-Cell Lung Cancer: Study Protocol

Abstract The treatment outcome has been unsatisfactory for patients with non–small‐cell lung cancer (NSCLC) refractory to standard first‐line chemotherapy. Trastuzumab emtansine (T‐DM1), an anti‐HER2 antibody conjugated with a vinca alkaloid, has been approved for clinical use in HER2+ breast cancer in many countries. Approximately 5% of NSCLC tumors possess HER2 alterations, and T‐DM1 has shown excellent antitumor effects against HER2+ lung cancer cell lines in preclinical models. Therefore, we hypothesized that T‐DM1 could significantly inhibit the growth of HER2+ lung cancers. We have launched a nonrandomized phase II trial of T‐DM1 monotherapy for patients with HER2+ lung cancers. The major eligibility criteria are as follows: age ≥ 20 years, pathologically diagnosed NSCLC with documented HER2 positivity (immunohistochemistry 3+, both immunohistochemistry 2+ and fluorescence in situ hybridization positive, or exon 20 insertion mutation), and previous chemotherapy. Thirty patients will receive T‐DM1 3.6 mg/kg every 3 weeks. The primary endpoint is the overall response rate. This trial will provide information on whether T‐DM1 monotherapy is effective against HER2+ lung cancer.

Protocol Design for the Bench to Bed Trial in Alectinib-Refractory Non–Small-Cell Lung Cancer Patients Harboring the EML4-ALK Fusion Gene (ALRIGHT/OLCSG1405)

Based on our preclinical study results, which showed that the activation of the hepatocyte growth factor/MET pathway is a potential mechanism of acquired resistance to alectinib, we launched the ALRIGHT (OLCSG1405 [alectinib-refractory non-small-cell lung cancer patients harboring the EML4-ALK fusion gene]), a phase II trial of the anaplastic lymphoma kinase (ALK)/MET inhibitor crizotinib in patients with non-small-cell lung cancer refractory to alectinib and harboring the echinoderm microtubule-associated protein-like 4 (EML4)-ALK fusion gene. Patients with ALK-rearranged tumors who have developed disease progression during alectinib treatment will receive crizotinib monotherapy until disease progression or the occurrence of unacceptable toxicity. The primary endpoint is set as the objective response rate, assuming that a response in 50% of eligible patients will indicate potential usefulness and that 15% would be the lower limit of interest (1-sided α of 0.05, β of 0.20). The estimated accrual number of patients is 9. The secondary endpoints include progression-free survival, overall survival, adverse events, and patient-reported outcomes. We will also take tissue samples before crizotinib monotherapy to conduct an exploratory analysis of ALK and hepatocyte growth factor/MET expression levels and gene alterations (eg, mutations, amplifications, and translocations). We will obtain information regarding whether crizotinib, which targets not only ALK, but also MET, can truly produce efficacy with acceptable safety profiles in ALK+ non-small-cell lung cancer even in the alectinib-refractory setting.