Eri Banno

Sensitivities to various epidermal growth factor receptor-tyrosine kinase inhibitors of uncommon epidermal growth factor receptor mutations L861Q and S768I: What is the optimal epidermal growth factor receptor-tyrosine kinase inhibitor?

Most patients with non‐small cell lung cancer (NSCLC) harboring common epidermal growth factor receptor (EGFR) mutations, such as deletions in exon 19 or the L858R mutation in exon 21, respond dramatically to EGFR tyrosine kinase inhibitors (EGFR‐TKI), and their sensitivities to various EGFR‐TKI have been well characterized. Our previous article showed the in vitro sensitivities of EGFR exon 18 mutations to EGFR‐TKI, but little information regarding the sensitivities of other uncommon EGFR mutations is available. First, stable transfectant Ba/F3 cell lines harboring EGFR L858R (Ba/F3‐L858R), L861Q (Ba/F3‐L861Q) or S768I (Ba/F3‐S768I) mutations were created and their drug sensitivities to various EGFR‐TKI were examined. Both the Ba/F3‐L861Q and Ba/F3‐S768I cell lines were less sensitive to erlotinib, compared with the Ba/F3‐L858R cell line, but their sensitivities to afatinib were similar to that of the Ba/F3‐L858R cell line. The Ba/F3‐L861Q cell line was similarly sensitive and the Ba/F3‐S768I cell line was less sensitive to osimertinib, compared with the Ba/F3‐L858R cell line. The results of western blot analyses were consistent with these sensitivities. Next, similar experiments were also performed using the KYSE270 (L861Q) and KYSE 450 (S768I) cell lines, and their results were compatible with those of the transfectant Ba/F3 cell lines. Our findings suggest that NSCLC harboring the EGFR L861Q mutation might be sensitive to afatinib or osimertinib and that NSCLC harboring the EGFR S768I mutation might be sensitive to afatinib. Overall, afatinib might be the optimal EGFR‐TKI against these uncommon EGFR mutations.

Activated MET acts as a salvage signal after treatment with alectinib, a selective ALK inhibitor, in ALK-positive non-small cell lung cancer

Non-small cell lung cancer (NSCLC) carrying echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) rearrangements is hypersensitive to ALK inhibitors, including crizotinib and alectinib. Crizotinib was initially designed as a MET inhibitor, whereas alectinib is a selective ALK inhibitor. The MET signal, which is inhibited by crizotinib but not by alectinib, is dysregulated in many human cancers. However, the role of the MET signal in ALK-positive NSCLC remains unclear. In this study, we found that hepatocyte growth factor (HGF), ligand of MET, mediated the resistance to alectinib, but not to crizotinib, via the MET signal in ALK-positive NSCLC cell lines (H3122 and H2228 cell lines). In addition, alectinib activated the MET signal even in the absence of HGF and the inhibition of the MET signal enhanced the efficacy of alectinib. These findings suggest that activated MET acts as a salvage signal in ALK-positive NSCLC. This novel role of the MET signal in ALK-positive NSCLC may pave the way for further clinical trials examining MET inhibitors.

MEK inhibitor for gastric cancer with MEK1 gene mutations

The prognosis for patients with unresectable advanced or recurrent gastric cancer remains poor. The identification of additional oncogenes with influences similar to those of epidermal growth factor receptor gene mutations, upon which the growth of cancer cells is dependent, is needed. In this study, we evaluated sensitivity to MEK inhibitors (GSK1120212 and PD0325901) in several gastric cancer cell lines in vitro and found three poorly differentiated gastric cancer cell lines that were hypersensitive to the inhibitors. The sequence analyses in these three cell lines revealed that one cell line had a novel MEK1 mutation, while the other two had previously reported KRAS and MEK1 mutations, respectively; the gene statuses of the other resistant cell lines were all wild-type. Experiments using MEK1 expression vectors demonstrated that the MEK1 mutations induced the phosphorylation of ERK1/2 and had a transforming potential, enhancing the tumorigenicity. The MEK inhibitor dramatically reduced the phosphorylation of ERK1/2 and induced apoptosis in the cell lines with MEK1 mutations. In vivo, tumor growth was also dramatically decreased by an inhibitor. One of the 46 gastric cancer clinical samples that were examined had a MEK1 mutation; this tumor had a poorly differentiated histology. Considering the addiction of cancer cells to active MEK1 mutations for proliferation, gastric cancer with such oncogenic MEK1 mutations might be suitable for targeted therapy with MEK inhibitors. Mol Cancer Ther; 13(12); 3098–106. ©2014 AACR.

FGFR gene alterations in lung squamous cell carcinoma are potential targets for the multikinase inhibitor nintedanib.

Fibroblast growth factor receptor (FGFR) gene alterations are relatively frequent in lung squamous cell carcinoma (LSCC) and are a potential targets for therapy with FGFR inhibitors. However, little is known regarding the clinicopathologic features associated with FGFR alterations. The angiokinase inhibitor nintedanib has shown promising activity in clinical trials for non‐small cell lung cancer. We have now applied next‐generation sequencing (NGS) to characterize FGFR alterations in LSCC patients as well as examined the antitumor activity of nintedanib in LSCC cell lines positive for FGFR1 copy number gain (CNG). The effects of nintedanib on the proliferation of and FGFR signaling in LSCC cell lines were examined in vitro, and its effects on tumor formation were examined in vivo. A total of 75 clinical LSCC specimens were screened for FGFR alterations by NGS. Nintedanib inhibited the proliferation of FGFR1 CNG‐positive LSCC cell lines in association with attenuation of the FGFR1–ERK signaling pathway in vitro and in vivo. FGFR1 CNG (10.7%), FGFR1 mutation (2.7%), FGFR2 mutation (2.7%), FGFR4 mutation (5.3%), and FGFR3 fusion (1.3%) were detected in LSCC specimens by NGS. Clinicopathologic features did not differ between LSCC patients positive or negative for FGFR alterations. However, among the 36 patients with disease recurrence after surgery, prognosis was significantly worse for those harboring FGFR alterations. Screening for FGFR alterations by NGS warrants further study as a means to identify patients with LSCC recurrence after surgery who might benefit from nintedanib therapy.

An activating ALK gene mutation in ALK IHC-positive/FISH-negative nonsmall-cell lung cancer

ABSTRACT The detection of ALK rearrangements is mainly performed using fluorescence in-situ hybridization (FISH). However, such analyses can yield false-positive and false-negative results. Other ALK diagnostic techniques have been developed, including immunohistochemistry (IHC) for the detection of the chimeric ALK protein and a reverse transcriptase-polymerase chain reaction analysis to search for the presence of abnormal fusion transcript. Some studies have reported significant clinical improvement after treatment with crizotinib in patients with tumors that were designated as ALK-negative by FISH but were found to be ALK-positive by IHC. In the present study, we identified an ALK R1192G mutation in an NSCLC clinical sample with ALK IHC-positive/FISH-negative findings and showed that this mutation was an oncogenic activating mutation. In addition, ALK inhibitors were likely to be effective against NSCLC cells carrying this mutation. To the best of our knowledge, this is the first study to show that a clinical sample with ALK IHC-positive/FISH-negative findings has an ALK activating mutation. Although this patient has not been treated with any ALK inhibitors because of no recurrence, ALK inhibitors can be effective against such NSCLC cells. To ensure that candidates for treatment with ALK inhibitors are not missed, further comprehensive analyses, such as next generation sequencing, should be introduced into clinical practice.

Significance of FGF9 gene in resistance to anti-EGFR therapies targeting colorectal cancer: A subset of colorectal cancer patients with FGF9 upregulation may be resistant to anti-EGFR therapies

Although fibroblast growth factor (FGF) signals are strongly associated with malignancy, limited information is available regarding the role of the FGF9 signal in colorectal cancer (CRC). In this study, we investigated the frequency of FGF9 amplification in CRC clinical specimens and the association between the FGF9 gene and resistance to anti‐EGFR therapies. In clinical samples, an FGF9 copy number gain of >5 copies was observed at a frequency of 8/145 (5.5%) and tended to be related to wild‐type KRAS (7/96, 7.3%). Furthermore, FGF9 amplification was not observed in any of the samples from the 15 responders to anti‐EGFR therapies but was observed in one sample from the seven non‐responders with wild‐type KRAS, and two samples from non‐responders also had high FGF9 mRNA expression levels. FGF9 amplification was validated using a fluorescence in situ hybridization (FISH) analysis, and FGF9‐amplified sections showed readily detectable signals originating from FGF9 protein when examined using immunohistochemistry. In both the in vitro and in vivo experiments using FGF9‐overexpressing CRC cell lines, FGF9 overexpression induced strong resistance to anti‐EGFR therapies via the enforced FGFR signal, and this resistance was cancelled by the application of an FGFR inhibitor. Considering these results, the FGF9 gene may play an important role in resistance to anti‐EGFR therapies in patients with CRC, and such resistance might be overcome by combined treatment with an anti‐FGFR inhibitor. These findings strongly encourage the development of FGFR‐targeted therapy for CRC patients with FGF9 gene upregulation.

MEK inhibitors against MET-amplified non-small cell lung cancer

Several receptor tyrosine kinases (RTKs) including EGFR, ALK, and MET have been identified as therapeutic targets in non-small cell lung cancer (NSCLC). Among the downstream pathways of RTKs, the MAPK pathway is particularly important for cancer cell proliferation, differentiation, and survival. In this study, the effects of MEK inhibitors (trametinib and PD0325901) in several NSCLC cell lines with driver gene alterations, especially RTK genes, were tested in vitro using an MTT assay, and a wide range of sensitivities was found. In particular, all the EGFR-mutated cell lines were resistant to MEK inhibitors, whereas all the MET-amplified cell lines were sensitive. A bioinformatics technique and western blot analyses showed that the PI3K/AKT pathway is more activated in EGFR-mutated NSCLC than in MET-amplified NSCLC, and a PI3K inhibitor enhanced the sensitivity to trametinib in the EGFR-mutated cell lines, suggesting that this pathway is associated with resistance to MEK inhibitors. Although the HCC827 cell line (EGFR mutation) was resistant to MEK inhibitors, the HCC827CNXR cell line, whose driver gene shifts from EGFR to MET, exhibited enhanced sensitivity to MEK inhibitors, indicating the biological importance of the MAPK pathway for MET-amplified NCSLC. Furthermore, a synergistic effect of crizotinib (a MET inhibitor) and trametinib was observed in MET-amplified NCLC cell lines. Our findings indicate that the MAPK pathway is biologically important for MET-amplified NSCLC and strongly encourage the development of combination therapy with a MET inhibitor and a MEK inhibitor against MET-amplified NSCLC.

Functional Analyses of Mutations in Receptor Tyrosine Kinase Genes in Non–Small Cell Lung Cancer: Double-Edged Sword of DDR2

Purpose: This study investigated whether mutations of receptor tyrosine kinase (RTK) genes detected using next-generation sequencing (NGS) are suitable therapeutic targets. Experimental design: Fifty surgically resected non–small cell lung cancer (NSCLC) samples were target resequenced using NGS. We then investigated the functions of the identified RTK gene mutations, including their oncogenic potential, in vitro. Results: Mutations in RTK genes were found in 20 samples (EGFR, 15; ERBB4, 1; ALK, 1; DDR2, 2; FGFR1, 1), mutations in MAPK pathway genes were found in nine samples (KRAS, 7; NRAS, 1; BRAF, 2), and mutations in PI3K pathway genes were found in three samples (PIK3CA, 1; PTEN, 3). Among the mutations in RTKs, the functions of four mutations were unclear (ERBB4 D245G; DDR2 H246R and E655K; FGFR1 A263V). These mutations did not exhibit any transformational activities. Neither the phosphorylation nor the protein expressions of RTKs were changed by the DDR2 H246R, ERBB4 D245G, and FGFR1 A263V mutations, although the expression level of the DDR2 protein harboring the E655K mutation was particularly low. Collagen stimulation decreased cellular proliferation through p38 activation in the DDR2 wild-type–overexpressed cell lines, whereas the growth-suppressive effect was weakened in DDR2 E655K–overexpressed cell lines. Furthermore, the DDR2 E655K protein strongly bound to ubiquitin ligase E3 (Cbl-b), and the mutant protein expression was increased after treatment with a proteasome inhibitor. Conclusions: Our experimental findings suggest that RTK mutations are not always suitable as therapeutic targets. The DDR2 E655K mutation can play a role in cancer progression by reducing the growth-inhibitory effect of collagen. Clin Cancer Res; 22(14); 3663–71. ©2016 AACR.

EGFR and HER2 signals play a salvage role in MEK1-mutated gastric cancer after MEK inhibition

Since the prognosis of unresectable advanced gastric cancer remains poor, novel therapeutic strategies are needed. Somatic MEK1 gene mutations have been reported as oncogenic activating mutations in gastric cancer, and MEK inhibitors can be effective against such gastric cancers. In the present study, however, activated EGFR and HER2 signals after treatment with a MEK inhibitor (trametinib) were found in a MEK1-mutated gastric cancer cell line (OCUM-1 cell line) using a phospho-receptor tyrosine kinase array. The phosphorylation of EGFR and HER2 reactivated ERK1/2, which had been inhibited by trametinib, and EGF stimulation led to resistance to trametinib in this cell line. Lapatinib, an EGFR and an HER2 inhibitor, reversed the activation of ERK1/2 by inhibiting the phosphorylation of EGFR and HER2 and cancelled the resistance. The combination of trametinib and lapatinib synergistically inhibited the cell growth of the OCUM-1 cell line and strongly induced apoptosis by inhibiting the activated EGFR and HER2 signals. These results suggest that the EGFR and HER2 signals play a salvage role and are related to resistance to MEK inhibitors in MEK1‑mutated gastric cancer. Moreover, combination therapy with trametinib and lapatinib can exhibit a synergistic effect and may contribute to overcoming the resistance to MEK inhibitors.

Afatinib against Esophageal or Head-and-Neck Squamous Cell Carcinoma: Significance of Activating Oncogenic HER4 Mutations in HNSCC

The prognosis for patients with advanced esophageal or head-and-neck squamous cell carcinoma (ESCC or HNSCC) remains poor, and the identification of additional oncogenes and their inhibitors is needed. In this study, we evaluated the sensitivities of several ESCC and HNSCC cell lines to HER inhibitors (cetuximab, erlotinib, and afatinib) in vitro and found two cell lines that were hypersensitive to afatinib. Sequence analyses for the afatinib-targeted HER family genes in the two cell lines revealed that one cell line had a previously reported activating EGFR L861Q mutation, whereas the other had an HER4 G1109C mutation of unknown function. No amplification of HER family genes was found in either of the two cell lines. The phosphorylation level of HER4 was elevated in the HER4 G1109C mutation-overexpressed HEK293 cell line, and the mutation had a transforming potential and exhibited tumorigenicity in an NIH3T3 cell line, indicating that this HER4 mutation was an activating oncogenic mutation. Afatinib dramatically reduced the phosphorylation level of EGFR or HER4 and induced apoptosis in the two cell lines. In vivo, tumor growth was also dramatically decreased by afatinib. In a database, the frequencies of HER family gene mutations in ESCC or HNSCC ranged from 0% to 5%. In particular, HER4 mutations have been found relatively frequently in HNSCC. Considering the addiction of cancer cells to activating oncogenic EGFR or HER4 mutations for proliferation, HNSCC or ESCC with such oncogenic mutations might be suitable for targeted therapy with afatinib. Mol Cancer Ther; 15(8); 1988–97. ©2016 AACR.