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// Su Jin Lee 1, * , Gang Gary Li 2, * , Seung Tae Kim 1, * , Min Eui Hong 3 , Jiryeon Jang 1 , Nara Yoon 3 , Soo Min Ahn 3 , Danielle Murphy 2 , Jason Christiansen 2 , Ge Wei 2 , Zachary Hornby 2 , Dong Woo Lee 4 , Joon Oh Park 1, 7 , Young Suk Park 1 , Ho Yeong Lim 1 , Sung No Hong 5 , Seok-Hyeong Kim 3 , Won Ki Kang 1 , Keunchil Park 1 , Woong Yang Park 6 , Kyoung-Mee Kim 3, 7 , Jeeyun Lee 1 1 Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea 2 Ignyta Inc, San Diego, California, USA 3 Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea 4 Samsung Electrics, Seoul, Korea 5 Division of Gastroenterology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea 6 Samsung Genome Institute, Seoul, Korea 7 The Innovative Cancer Medicine Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea * These authors have contributed equally to this work Correspondence to: Jeeyun Lee, e-mail: jyunlee@skku.edu Kyoung-Mee Kim, e-mail: kkmkys@skku.edu Keywords: colorectal cancer, NTRK1 rearrangement, TRKA immunohistochemistry Received: June 22, 2015 Accepted: September 30, 2015 Published: October 12, 2015 ABSTRACT Background: We have investigated the incidence of NTRK1 rearrangements in metastatic gastrointestinal cancer patients and demonstrated the potential for clinical response of these patients to targeted therapy. Methods: We prospectively collected tumor tissue specimens for one year and simultaneously generated patient-derived tumor cells (PDCs). Specimens were initially screened for TrkA protein expression using TrkA immunohistochemistry (IHC). In the case of TrkA IHC positive results, samples were further examined by fluorescence in situ hybridization (FISH) and next generation sequencing (NGS) to confirm the presence of NTRK1 rearrangements. Results: From January 2014 to December 2014, a total of 74 metastatic colorectal cancer (CRC) patients and 66 gastric cancer (GC) patients were initially screened by TrkA IHC. Two of the 74 CRC patients (2.7%) and one of the 66 GC patients (1.5%) were positive for TrkA expression by IHC. All three IHC positive cases had evidence of NTRK1 rearrangements by FISH. NGS was performed on the 3 IHC positive cases and confirmed TPM3- NTRK1 rearrangements in the two CRC cases. One GC patient with TrkA expression by IHC did not harbor an NTRK1 rearrangement. PDCs established from the NTRK1 positive CRC patients were positive for the NTRK1 rearrangement. Entrectinib, a pan-TRK inhibitor, profoundly inhibited cell proliferation of NTRK1 -rearranged PDCs with such inhibition associated with inactivation of TrkA, and down-regulation of downstream signaling pathways. Conclusion: TrkA IHC is an effective, initial screening method for NTRK1 rearrangement detection in the clinic. Inhibition of the TrkA kinase is a promising targeted therapy for cancer patients whose tumors harbor a NTRK1 rearrangement.

// Jeeyun Lee 1, * , Hee Cheol Kim 2, * , Jung Yong Hong 3, * , Kai Wang 4 , Sun Young Kim 1 , Jiryeon Jang 1 , Seung Tae Kim 1 , Joon Oh Park 1 , Ho Yeong Lim 1 , Won Ki Kang 1 , Young Suk Park 1 , Jiyun Lee 1 , Woo Yong Lee 2 , Yoon Ah Park 2 , Jung Wook Huh 2 , Seong Hyeon Yun 2 , In-Gu Do 5 , Seok Hyung Kim 5 , Sohail Balasubramanian 4 , Philip J. Stephens 4 , Jeffrey S. Ross 4, 6 , Gang Gary Li 7 , Zachary Hornby 7 , Siraj M. Ali 4 , Vincent A. Miller 4 , Kyoung-Mee Kim 5, 8 , Sai-Hong Ignatius Ou 9 1 Department of Medicine, Division of Hematology-Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea 2 Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea 3 Department of Internal Medicine, Chung-Ang University College of Medicine, Dongjak-Gu, Seoul, Republic of Korea 4 Foundation Medicine Inc, Cambridge, Massachusetts, USA 5 Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea 6 Department of Pathology and Laboratory Medicine, Albany Medical College, Albany, New York, USA 7 Ignyta Inc, San Diego, California, USA 8 Innovative Cancer Medicine Institute, Samsung Medical Center, Seoul, Korea 9 Chao Family Comprehensive Cancer Center, University of California Irvine School of Medicine, Orange, California, USA * These authors have contributed equally to this work Correspondence to: Sai-Hong Ignatius Ou, e-mail: Ignatius.ou@uci.edu Kyoung-Mee Kim, e-mail: kkmkys@skku.edu Keywords: colorectal carcinoma, anaplastic lymphoma kinase (ALK) rearrangement, immunohistochemistry, next generation sequencing Received: April 02, 2015 Accepted: June 19, 2015 Published: July 01, 2015 ABSTRACT Purpose: Anaplastic lymphoma kinase (ALK) rearrangement has been detected in colorectal carcinoma (CRC) using advanced molecular diagnostics tests including exon scanning, fluorescence in situ hybridization (FISH), and next generation sequencing (NGS). We investigated if immunohistochemistry (IHC) can be used to detect ALK rearrangement in gastrointestinal malignancies. Experimental designs: Tissue microarrays (TMAs) from consecutive gastric carcinoma (GC) and CRC patients who underwent surgical resection at Samsung Medical Center, Seoul, Korea were screened by IHC using ALK monoclonal antibody 5A4. IHC positive cases were confirmed by FISH, nCounter assays, and NGS-based comprehensive genomic profiling (CGP). ALK IHC was further applied to CRC patients enrolled in a pathway-directed therapeutic trial. Results: Four hundred thirty-two GC and 172 CRC cases were screened by IHC. No GC sample was ALK IHC positive. One CRC (0.6%) was ALK IHC positive (3+) that was confirmed by ALK FISH and a novel CAD-ALK (C35; A20) fusion variant that resulted from a paracentric inversion event inv(2)(p22–21p23) was identified by CGP. One out of 50 CRC patients enrolled in a pathway-directed therapeutic trial was ALK IHC positive (3+) confirmed by ALK FISH and found to harbor the EML4-ALK (E21, A20) fusion variant by CGP. Growth of a tumor cell line derived from this EML4-ALK CRC patient was inhibited by ALK inhibitors crizotinib and entrectinib. Conclusions: ALK IHC is a viable screening strategy for identifying ALK rearrangement in CRC. ALK rearrangement is a potential actionable driver mutation in CRC based on survival inhibition of patient tumor-derived cell line by potent ALK inhibitors.