BACKGROUND: Several lines of evidence indicate that mutational activation of KRAS is an early event in the carcinogenesis of non-small cell lung cancer (NSCLC). Nonetheless, previous studies report high frequencies of divergent KRAS mutational status between primary NSCLC and corresponding metastases. This suggests heterogeneity of the primary tumor in respect to its KRAS status. We therefore aimed to examine the frequency and the extent of such intratumoral heterogeneity. METHODS: 40 NSCLC were examined for intratumoral heterogeneity of KRAS mutation (20 adenocarcinomas, 10 squamous cell carcinomas and 10 large cell carcinomas). Three to eight different tumor areas were analyzed for KRAS mutation and up to four corresponding lymph node metastases were included for analysis in nineteen cases. A combination of different methods for screening of heterogeneity and its validation were used including direct sequencing, laser-capture microdissection for tumor cell enrichment and the very sensitive ARMS/S method. RESULTS: Mutations of KRAS were found in 13/30 adenocarcinomas and large cell carcinomas. No mutations were detected in 10 squamous cell carcinomas. Four cases showed heterogeneous KRAS results by direct sequencing. More sensitive methods for KRAS mutation analysis revealed false negative results due to admixture of non-neoplastic cells in all of these samples. Intratumoral heterogeneity of KRAS mutational status was therefore confirmed in none of the analyzed cases. In addition, identical KRAS mutations were present in the primary tumor and the corresponding lymph node metastases in 19 cases examined. CONCLUSIONS: Intratumoral heterogeneity of KRAS mutational status is rare in NSCLC but highly sensitive tools are required to reliably identify these mutations. This finding is in line with the hypothesis that oncogenic activation of KRAS is an early event and a bona fide "driver mutation" in NSCLC. Furthermore, future therapies targeting KRAS will not be limited by intratumoral heterogeneity.
BACKGROUND: Several lines of evidence indicate that mutational activation of KRAS is an early event in the carcinogenesis of non-small cell lung cancer (NSCLC). Nonetheless, previous studies report high frequencies of divergent KRAS mutational status between primary NSCLC and corresponding metastases. This suggests heterogeneity of the primary tumor in respect to its KRAS status. We therefore aimed to examine the frequency and the extent of such intratumoral heterogeneity. METHODS: 40 NSCLC were examined for intratumoral heterogeneity of KRAS mutation (20 adenocarcinomas, 10 squamous cell carcinomas and 10 large cell carcinomas). Three to eight different tumor areas were analyzed for KRAS mutation and up to four corresponding lymph node metastases were included for analysis in nineteen cases. A combination of different methods for screening of heterogeneity and its validation were used including direct sequencing, laser-capture microdissection for tumor cell enrichment and the very sensitive ARMS/S method. RESULTS: Mutations of KRAS were found in 13/30 adenocarcinomas and large cell carcinomas. No mutations were detected in 10 squamous cell carcinomas. Four cases showed heterogeneous KRAS results by direct sequencing. More sensitive methods for KRAS mutation analysis revealed false negative results due to admixture of non-neoplastic cells in all of these samples. Intratumoral heterogeneity of KRAS mutational status was therefore confirmed in none of the analyzed cases. In addition, identical KRAS mutations were present in the primary tumor and the corresponding lymph node metastases in 19 cases examined. CONCLUSIONS: Intratumoral heterogeneity of KRAS mutational status is rare in NSCLC but highly sensitive tools are required to reliably identify these mutations. This finding is in line with the hypothesis that oncogenic activation of KRAS is an early event and a bona fide "driver mutation" in NSCLC. Furthermore, future therapies targeting KRAS will not be limited by intratumoral heterogeneity.
Authors: Li-Hui Tseng; Federico De Marchi; Aparna Pallavajjalla; Erika Rodriguez; Rena Xian; Deborah Belchis; Christopher D Gocke; James R Eshleman; Peter Illei; Ming-Tseh Lin Journal: Am J Clin Pathol Date: 2019-10-07 Impact factor: 2.493
Authors: Vincent L Cannataro; Stephen G Gaffney; Carly Stender; Zi-Ming Zhao; Mark Philips; Andrew E Greenstein; Jeffrey P Townsend Journal: Oncogene Date: 2018-02-16 Impact factor: 9.867
Authors: Justin F Gainor; Anna M Varghese; Sai-Hong Ignatius Ou; Sheheryar Kabraji; Mark M Awad; Ryohei Katayama; Amanda Pawlak; Mari Mino-Kenudson; Beow Y Yeap; Gregory J Riely; A John Iafrate; Maria E Arcila; Marc Ladanyi; Jeffrey A Engelman; Dora Dias-Santagata; Alice T Shaw Journal: Clin Cancer Res Date: 2013-05-31 Impact factor: 12.531
Authors: Eun Young Kim; Eun Na Cho; Heae Surng Park; Arum Kim; Ji Young Hong; Seri Lim; Jong Pil Youn; Seung Yong Hwang; Yoon Soo Chang Journal: BMC Cancer Date: 2016-01-18 Impact factor: 4.430
Authors: Marcin Nicoś; Paweł Krawczyk; Bożena Jarosz; Marek Sawicki; Justyna Szumiłło; Tomasz Trojanowski; Janusz Milanowski Journal: Clin Exp Med Date: 2015-04-23 Impact factor: 3.984
Authors: Jacek Kordiak; Janusz Szemraj; Izabela Grabska-Kobylecka; Piotr Bialasiewicz; Marcin Braun; Radzisław Kordek; Dariusz Nowak Journal: J Cancer Res Clin Oncol Date: 2018-10-27 Impact factor: 4.553