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Identification of a lung adenocarcinoma cell line with CCDC6-RET fusion gene and the effect of RET inhibitors in vitro and in vivo.

ABSTRACT: Rearrangements of the proto-oncogene RET are newly identified potential driver mutations in lung adenocarcinoma (LAD). However, the absence of cell lines harboring RET fusion genes has hampered the investigation of the biological relevance of RET and the development of RET-targeted therapy. Thus, we aimed to identify a RET fusion positive LAD cell line. Eleven LAD cell lines were screened for RET fusion transcripts by reverse transcription-polymerase chain reaction. The biological relevance of the CCDC6-RET gene products was assessed by cell growth, survival and phosphorylation of ERK1/2 and AKT with or without the suppression of RET expression using RNA interference. The efficacy of RET inhibitors was evaluated in vitro using a culture system and in an in vivo xenograft model. Expression of the CCDC6-RET fusion gene in LC-2/ad cells was demonstrated by the mRNA and protein levels, and the genomic break-point was confirmed by genomic DNA sequencing. Mutations in KRAS and EGFR were not observed in the LC-2/ad cells. CCDC6-RET was constitutively active, and the introduction of a siRNA targeting the RET 3' region decreased cell proliferation by downregulating RET and ERK1/2 phosphorylation. Moreover, treatment with RET-inhibitors, including vandetanib, reduced cell viability, which was accompanied by the downregulation of the AKT and ERK1/2 signaling pathways. Vandetanib exhibited anti-tumor effects in the xenograft model. Endogenously expressing CCDC6-RET contributed to cell growth. The inhibition of kinase activity could be an effective treatment strategy for LAD. LC-2/ad is a useful model for developing fusion RET-targeted therapy.

SUBMITTER: Suzuki M

PROVIDER: S-EPMC7657251 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Identification of a lung adenocarcinoma cell line with CCDC6-RET fusion gene and the effect of RET inhibitors in vitro and in vivo.

Suzuki Makito M Makinoshima Hideki H Matsumoto Shingo S Suzuki Ayako A Mimaki Sachiyo S Matsushima Koutatsu K Yoh Kiyotaka K Goto Koichi K Suzuki Yutaka Y Ishii Genichiro G Ochiai Atsushi A Tsuta Koji K Shibata Tatsuhiro T Kohno Takashi T Esumi Hiroyasu H Tsuchihara Katsuya K

Cancer science 20130512 7

Rearrangements of the proto-oncogene RET are newly identified potential driver mutations in lung adenocarcinoma (LAD). However, the absence of cell lines harboring RET fusion genes has hampered the investigation of the biological relevance of RET and the development of RET-targeted therapy. Thus, we aimed to identify a RET fusion positive LAD cell line. Eleven LAD cell lines were screened for RET fusion transcripts by reverse transcription-polymerase chain reaction. The biological relevance of t ...[more]

PMID: 23578175

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Project description:Multi-kinase RET inhibitors, such as cabozantinib and RXDX-105, are active in lung cancer patients with RET fusions; however, the overall response rates to these two drugs are unsatisfactory compared to other targeted therapy paradigms. Moreover, these inhibitors may have different efficacies against RET rearrangements depending on the upstream fusion partner. A comprehensive preclinical analysis of the efficacy of RET inhibitors is lacking due to a paucity of disease models harboring RET rearrangements. Here we generated two new patient-derived xenograft (PDX) models, one new patient-derived cell line, one PDX-derived cell line, and several isogenic cell lines with RET fusions. Using these models, we re-examined the efficacy and mechanism of action of cabozantinib and found that this RET inhibitor was effective at blocking growth of cell lines, activating caspase 3/7 and inhibiting activation of ERK and AKT. Cabozantinib treatment of mice bearing RET-fusion-positive cell line xenografts and two PDXs significantly reduced tumor proliferation without adverse toxicity. Moreover, cabozantinib was effective at reducing growth of a lung cancer PDX that was not responsive to RXDX-105. Transcriptomic analysis of lung tumors and cell lines with RET alterations showed activation of a MYC signature and this was suppressed by treatment of cell lines with cabozantinib. MYC protein levels were rapidly depleted following cabozantinib treatment. Taken together, our results demonstrate that cabozantinib is an effective agent in preclinical models harboring RET rearrangements with three different 5' fusion partners (CCDC6, KIF5B and TRIM33). Notably, we identify MYC as a protein that is upregulated by RET expression and down-regulated by cabozantinib treatment, opening up potentially new therapeutic avenues for combinatorial targeting RET-fusion driven lung cancers. The novel RET fusion-dependent preclinical models described herein represent valuable tools for further refinement of current therapies and the evaluation of novel therapeutic strategies.

Project description:BackgroundRearranged during transfection (RET) gene fusions are a validated target in non-small-cell lung cancer (NSCLC). RET-selective inhibitors selpercatinib (LOXO-292) and pralsetinib (BLU-667) recently demonstrated favorable antitumor activity and safety profiles in advanced RET fusion-positive NSCLC, and both have received approval by the US Food and Drug Administration for this indication. Insights into mechanisms of resistance to selective RET inhibitors remain limited.Patients and methodsThis study was performed at five institutions. Tissue and/or cell-free DNA was obtained from patients with RET fusion-positive NSCLC after treatment with selpercatinib or pralsetinib and assessed by next-generation sequencing (NGS) or MET FISH.ResultsWe analyzed a total of 23 post-treatment tissue and/or plasma biopsies from 18 RET fusion-positive patients who received an RET-selective inhibitor (selpercatinib, n = 10; pralsetinib, n = 7; pralsetinib followed by selpercatinib, n = 1, with biopsy after each inhibitor). Three cases had paired tissue and plasma samples, of which one also had two serial resistant tissue specimens. The median progression-free survival on RET inhibitors was 6.3 months [95% confidence interval 3.6-10.8 months]. Acquired RET mutations were identified in two cases (10%), both affecting the RET G810 residue in the kinase solvent front. Three resistant cases (15%) harbored acquired MET amplification without concurrent RET resistance mutations, and one specimen had acquired KRAS amplification. No other canonical driver alterations were identified by NGS. Among 16 resistant tumor specimens, none had evidence of squamous or small-cell histologic transformation.ConclusionsRET solvent front mutations are a recurrent mechanism of RET inhibitor resistance, although they occurred at a relatively low frequency. The majority of resistance to selective RET inhibition may be driven by RET-independent resistance such as acquired MET or KRAS amplification. Next-generation RET inhibitors with potency against RET resistance mutations and combination strategies are needed to effectively overcome resistance in these patients.

Dataset Information

Identification of a lung adenocarcinoma cell line with CCDC6-RET fusion gene and the effect of RET inhibitors in vitro and in vivo.

Publications

Identification of a lung adenocarcinoma cell line with CCDC6-RET fusion gene and the effect of RET inhibitors in vitro and in vivo.

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