Kohei Otsubo

Capturing the mammalian Hippo: Elucidating its role in cancer

The Hippo pathway is an evolutionarily conserved kinase cascade involved in cell growth, apoptosis, development and migration. It is also crucial for stem cell self‐renewal and the maintenance of genomic stability. In addition, this pathway has the unique capacities to sense aspects of tissue architecture, such as cell polarity and mechanical tensions imposed by the surrounding microenvironment, and to control organ size and shape. All of these properties are frequently altered in tumor cells. In this review, we summarize how dysregulation of mammalian Hippo signaling is implicated in cancer.

Acquisition of the T790M resistance mutation during afatinib treatment in EGFR tyrosine kinase inhibitor–naïve patients with non–small cell lung cancer harboring EGFR mutations

The T790M secondary mutation of the epidermal growth factor receptor (EGFR) gene accounts for 50% to 60% of cases of resistance to the first-generation EGFR tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib. The prevalence of T790M in EGFR mutation-positive patients who acquire resistance to the irreversible, second-generation EGFR-TKI afatinib has remained unclear, however. We here determined the frequency of T790M acquisition at diagnosis of progressive disease in patients with EGFR-mutated non-small cell lung cancer (NSCLC) treated with afatinib as first-line EGFR-TKI. Among 56 enrolled patients, 37 individuals underwent molecular analysis at rebiopsy. Of these 37 patients, 16 individuals (43.2%) had acquired T790M, including 11/21 patients (52.4%) with an exon 19 deletion of EGFR and 5/13 patients (38.5%) with L858R. None of three patients with an uncommon EGFR mutation harbored T790M. T790M was detected in 14/29 patients (48.3%) with a partial response to afatinib, 1/4 patients (25%) with stable disease, and 1/4 patients (25%) with progressive disease as the best response. Median progression-free survival after initiation of afatinib treatment was significantly (P = 0.043) longer in patients who acquired T790M (11.9 months; 95% confidence interval, 8.7-15.1) than in those who did not (4.5 months; 95% confidence interval, 2.0-7.0). Together, our results show that EGFR-mutated NSCLC patients treated with afatinib as first-line EGFR-TKI acquire T790M at the time of progression at a frequency similar to that for patients treated with gefitinib or erlotinib. They further underline the importance of rebiopsy for detection of T790M in afatinib-treated patients.The T790M secondary mutation of the epidermal growth factor receptor (EGFR) gene accounts for 50% to 60% of cases of resistance to the first-generation EGFR tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib. The prevalence of T790M in EGFR mutation–positive patients who acquire resistance to the irreversible, second-generation EGFR-TKI afatinib has remained unclear, however. We here determined the frequency of T790M acquisition at diagnosis of progressive disease in patients with EGFR-mutated non–small cell lung cancer (NSCLC) treated with afatinib as first-line EGFR-TKI. Among 56 enrolled patients, 37 individuals underwent molecular analysis at rebiopsy. Of these 37 patients, 16 individuals (43.2%) had acquired T790M, including 11/21 patients (52.4%) with an exon 19 deletion of EGFR and 5/13 patients (38.5%) with L858R. None of three patients with an uncommon EGFR mutation harbored T790M. T790M was detected in 14/29 patients (48.3%) with a partial response to afatinib, 1/4 patients (25%) with stable disease, and 1/4 patients (25%) with progressive disease as the best response. Median progression-free survival after initiation of afatinib treatment was significantly (P = 0.043) longer in patients who acquired T790M (11.9 months; 95% confidence interval, 8.7–15.1) than in those who did not (4.5 months; 95% confidence interval, 2.0–7.0). Together, our results show that EGFR-mutated NSCLC patients treated with afatinib as first-line EGFR-TKI acquire T790M at the time of progression at a frequency similar to that for patients treated with gefitinib or erlotinib. They further underline the importance of rebiopsy for detection of T790M in afatinib-treated patients.

Phase II trial of weekly nab-paclitaxel for previously treated advanced non-small cell lung cancer: Kumamoto thoracic oncology study group (KTOSG) trial 1301.

OBJECTIVES We performed an open-label, multicenter, single-arm phase II study (UMIN ID 000010532) to prospectively evaluate the efficacy and safety of nab-paclitaxel for previously treated patients with advanced non-small cell lung cancer (NSCLC). METHODS Patients with advanced NSCLC who experienced failure of prior platinum-doublet chemotherapy received weekly nab-paclitaxel (100mg/m(2)) on days 1, 8, and 15 of a 21-day cycle until disease progression or the development of unacceptable toxicity. The primary end point of the study was objective response rate (ORR). RESULTS Forty-one patients were enrolled between September 2013 and April 2015. The ORR was 31.7% (90% confidence interval, 19.3%-44.1%), which met the primary objective of the study. Median progression-free survival was 4.9 months (95% confidence interval, 2.4-7.4 months) and median overall survival was 13.0 (95% confidence interval, 8.0-18.0 months) months. The median number of treatment cycles was four (range, 1-17) over the entire study period, and the median dose intensity was 89.1mg/m(2) per week. Hematologic toxicities of grade 3 or 4 included neutropenia (19.5%) and leukopenia (17.1%), with no cases of febrile neutropenia being observed. Individual nonhematologic toxicities of grade 3 or higher occurred with a frequency of <5%. CONCLUSION Weekly nab-paclitaxel was associated with acceptable toxicity and a favorable ORR in previously treated patients with advanced NSCLC. Our results justify the undertaking of a phase III trial comparing nab-paclitaxel with docetaxel in this patient population.

Severe acute interstitial lung disease in a patient with anaplastic lymphoma kinase rearrangement–positive non–small cell lung cancer treated with alectinib

SummaryAlectinib, the second generation anaplastic lymphoma kinase (ALK) inhibitor, has significant potency in patients with ALK rearrangement positive non-small cell lung cancer (NSCLC), and its toxicity is generally well tolerable. We report a patient who developed severe acute interstitial lung disease after alectinib treatment. An 86-year-old woman with stage IV lung adenocarcinoma positive for rearrangement of ALK gene was treated with alectinib. On the 215th day after initiation of alectinib administration, she was admitted to our hospital with the symptom of progressive dyspnea. Computed tomography (CT) revealed diffuse ground glass opacities and consolidations in both lungs, and analysis of bronchoalveolar lavage fluid revealed pronounced lymphocytosis. There was no evidence of infection or other specific causes of her condition, and she was therefore diagnosed with interstitial lung disease induced by alectinib. Her CT findings and respiratory condition improved after steroid pulse therapy. As far as we are aware, this is the first reported case of alectinib-induced severe interstitial lung disease (ILD). We should be aware of the possibility of such a severe adverse event and should therefore carefully monitor patients treated with this drug.

MOB1-YAP1/TAZ-NKX2.1 axis controls bronchioalveolar cell differentiation, adhesion and tumour formation

Mps One Binder Kinase Activator (MOB)1A/1B are core components of the Hippo pathway. These proteins, which coactivate LArge Tumour Suppressor homologue kinases, are also tumour suppressors. To investigate MOB1A/B’s roles in normal physiology and lung cancer, we generated doxycycline (Dox)-inducible, bronchioalveolar epithelium-specific, null mutations of MOB1A/B in mice (SPC-rtTA/(tetO)7-Cre/Mob1aflox/flox/Mob1b−/−; termed luMob1DKO mice). Most mutants (70%) receiving Dox in utero (luMob1DKO (E6.5-18.5) mice) died of hypoxia within 1 h post-birth. Their alveolar epithelial cells showed increased proliferation, impaired YAP1/TAZ-dependent differentiation and decreased surfactant protein production, all features characteristic of human respiratory distress syndrome. Intriguingly, mutant mice that received Dox postnatally (luMob1DKO (P21–41) mice) did not develop spontaneous lung adenocarcinomas, and urethane treatment-induced lung tumour formation was decreased (rather than increased). Lungs of luMob1DKO (P21–41) mice exhibited increased detachment of bronchiolar epithelial cells and decreased numbers of the bronchioalveolar stem cells thought to initiate lung adenocarcinomas. YAP1/TAZ-NKX2.1-dependent expression of collagen XVII, a key hemidesmosome component, was also reduced. Thus, a MOB1-YAP1/TAZ-NKX2.1 axis is essential for normal lung homeostasis and expression of the collagen XVII protein necessary for alveolar stem cell maintenance in the lung niche.

Phase I study of salazosulfapyridine in combination with cisplatin and pemetrexed for advanced non‐small‐cell lung cancer

Spliced variant isoforms of CD44 (CD44v) are a marker of cancer stem cells in solid tumors. They stabilize the xCT subunit of the transporter system xc(–) and thereby promote synthesis of the antioxidant glutathione. Salazosulfapyridine (SASP) is an inhibitor of xCT and suppresses the proliferation of CD44v‐positive cancer cells. Chemotherapy‐naïve patients with advanced non‐squamous non‐small‐cell lung cancer were enrolled in a dose‐escalation study (standard 3 + 3 design) of SASP in combination with cisplatin and pemetrexed. The primary end‐point was the percentage of patients who experience dose‐limiting toxicity. Fifteen patients were enrolled in the study. Dose‐limiting toxicity was observed in one of six patients at a SASP dose of 1.5 g/day (elevation of aspartate and alanine aminotransferase levels, each of grade 3), two of five patients at 3 g/day (hypotension or pneumonitis, each of grade 3), and two of three patients at 4.5 g/day (anorexia of grade 3). The maximum tolerated dose was thus 3 g/day, and the recommended dose was 1.5 g/day. The overall response rate was 26.7% and median progression‐free survival was 11.7 months, much longer than that for cisplatin–pemetrexed alone in previous studies. Exposure to SASP varied markedly among individuals according to ABCG2 and NAT2 genotypes. The serum concentration of free CD44v protein was increased after the first cycle of treatment, possibly reflecting death of cancer stem cells. Salazosulfapyridine was thus given safely in combination with cisplatin–pemetrexed, with the addition of SASP tending to prolong progression‐free survival. This trial is registered in the UMIN Clinical Trials Registry as UMIN000017854.

PD-L1 expression in lung adenocarcinoma harboring EGFR mutations or ALK rearrangements

OBJECTIVES Expression of programmed cell death-ligand 1 (PD-L1) has been associated with clinical outcome of programmed cell death-1 (PD-1) pathway blockade in non-small cell lung cancer (NSCLC). The PD-L1 IHC 22C3 pharmDx assay, the only companion diagnostic for pembrolizumab therapy, has revealed that ∼30% of all NSCLCs express PD-L1 at a high level. The frequency of high PD-L1 expression in NSCLCs with known driver oncogenes has remained unclear, however. MATERIALS AND METHODS We retrospectively evaluated PD-L1 expression with the 22C3 assay in tumor tissue of 80 lung adenocarcinoma patients including 71 with EGFR mutations and 9 with ALK rearrangements, all of whom were treated with corresponding tyrosine kinase inhibitors (TKIs). RESULTS Of the 80 tumors analyzed, 26 (32.5%) had a PD-L1 tumor proportion score (TPS) of 1%-49% and 9 (11.3%) had a PD-L1 TPS of ≥50%; 35 (43.8%) thus had a PD-L1 TPS of ≥1%. Of the 71 tumors with EGFR mutations, 23 (32.4%) had a PD-L1 TPS of 1%-49% and 7 (9.9%) had a PD-L1 TPS of ≥50%. A PD-L1 TPS of ≥1% was not associated with any clinical characteristic examined. Progression-free survival on initial TKI treatment was significantly poorer for patients with a PD-L1 TPS of ≥1% than for those with a PD-L1 TPS of <1% (p = .016). CONCLUSIONS A subset of patients with EGFR mutations or ALK rearrangements had a PD-L1 TPS of ≥50%. Prospective studies are thus warranted to examine the efficacy of PD-1/PD-L1 inhibitors in such patients.

Treatment Rationale and Design for J-SONIC: A Randomized Study of Carboplatin Plus Nab-paclitaxel With or Without Nintedanib for Advanced Non–Small-cell Lung Cancer With Idiopathic Pulmonary Fibrosis

Abstract We describe the treatment rationale and procedure for a randomized study (J‐SONIC; University Hospital Medical Information Network Clinical Trials Registry identification no., UMIN000026799) of carboplatin plus nanoparticle albumin‐bound paclitaxel (nab‐paclitaxel) with or without nintedanib for patients with advanced non–small cell lung cancer (NSCLC) and idiopathic pulmonary fibrosis (IPF). The study was designed to examine the efficacy and safety of nintedanib administered with carboplatin plus nab‐paclitaxel versus carboplatin plus nab‐paclitaxel alone in chemotherapy‐naive patients with advanced NSCLC associated with IPF. Eligible patients (enrollment target, n = 170) will be randomized at a 1:1 ratio to receive 4 cycles of carboplatin (area under the curve, 6 on day 1) plus nab‐paclitaxel (100 mg/m2 on days 1, 8, and 15) administered every 3 weeks either without (arm A) or with (arm B) nintedanib (150 mg twice daily), to be followed in arm B by single‐agent administration of nintedanib (150 mg twice daily). The present trial is the first randomized controlled study for the treatment of NSCLC associated with IPF. The goal of the study is to demonstrate that nintedanib combined with carboplatin plus nab‐paclitaxel prolongs the interval to acute exacerbation of IPF compared with carboplatin plus nab‐paclitaxel alone.

Visualization and quantitation of epidermal growth factor receptor homodimerization and activation with a proximity ligation assay

Objectives Activation of the epidermal growth factor receptor (EGFR) results from receptor homodimerization and autophosphorylation and confers sensitivity to tyrosine kinase inhibitors in some tumors. However, the visual detection and quantitation of activated EGFR in the clinical setting has not been established. Materials and Methods A proximity ligation assay (PLA) was applied to detect EGFR homodimers in non–small cell lung cancer (NSCLC) cell lines and tissue specimens. Results PLA signals corresponding to EGFR homodimers were higher in NSCLC cell lines and tissue specimens positive for activating EGFR mutations than in those wild type (WT) for EGFR. Stimulation with EGF in NSCLC cells WT for EGFR or forced overexpression of EGFR in Ba/F3 cells resulted in marked EGFR homodimerization. The extent of EGFR homodimerization appeared related to that of EGFR autophosphorylation in NSCLC cells WT for EGFR. Conclusion PLA may provide a new tool for detection and quantitation of EGFR homodimers in NSCLC and other tumors.

Anticancer drug treatment for advanced lung cancer with interstitial lung disease

Interstitial lung disease (ILD) is a risk factor for lung cancer development and is frequently observed in patients with lung cancer. Individuals with ILD have been excluded from most prospective clinical trials of lung cancer therapies because of the risk of ILD acute exacerbation. Thus, the optimal anticancer drug treatment for such patients has yet to be established. Tyrosine kinase inhibitors are avoided for the treatment of advanced non-small cell lung cancer (NSCLC) with ILD because of the concern of acute exacerbation, and information on the effects of immune-checkpoint inhibitors is limited in these patients. Only three prospective single-arm studies of cytotoxic chemotherapies for advanced lung cancer with ILD have been reported. Based on the results of these studies and those of retrospective analyses, carboplatin and either paclitaxel or nab-paclitaxel are often selected in daily clinical practice for patients with NSCLC and ILD, whereas platinum plus etoposide is selected for those with small cell lung cancer and ILD. Although the antitumor activity of first-line platinum-based chemotherapy appears similar in advanced lung cancer patients with and without ILD, its impact on overall survival of the former patients is limited. The risks and benefits of chemotherapy must therefore be carefully explained before treatment initiation, and careful follow-up is necessary for such patients, especially those with the usual interstitial pneumonia pattern, a risk factor for chemotherapy-related exacerbation. Prospective clinical studies with large patient populations are still required to establish the appropriate treatments for advanced lung cancer with ILD.