A higher prevalence of MET amplification was also shown in advanced (pTNM III-IV) NSCLCs compared to early-stage (pTNM I-II) cases  [6], [9] and [22] and in stage IA ADCs compared to stage IB ones [17], as well

as in lymph node stage 2 metastases compared to primary tumors [23]. We also found a statistically significant association between MET copy gain and an increase in MET mRNA level in tumor tissue. The association between MET dosage status and the expression at protein level by immunohistochemistry has been explored in a number of studies and a strong correlation has invariably been shown [7], [16] and [17]. However, to our best knowledge, the present study is the

first investigation where this association was demonstrated at mRNA level, suggesting that MET overexpression in the cells with an increased gene CN at least partly learn more results from an enhanced transcription level. According to the present study, the rate of MET copy gain was found to be higher in the tumors harboring increased EGFR or HER2 CN and/or EGFR activating mutations as compared to the tumors without these alterations. However, these associations were statistically significant only in ADC cases (with the exception of the association with EGFR mutations that did not reach the statistical significance) but not in LCC or SCC tumors. However, C59 wnt no correlation between MET copy gain and KRAS dosage or mutational status was found. The association between EGFR and MET copy gains had been demonstrated previously [6], [9] and [20] and proposed to result from frequent chromosome 7 aneuploidy in cancer cells [6]. However, a concept of the functional cross from talk between MET and EGFR family receptors in cancer cells has also be suggested [10], [24] and [25]. The reported relations between increased MET CN and EGFR mutations are controversial. The alterations were found to be mutually exclusive in some studies [25] and [26], yet they coexisted

but not correlated in others [7], [17], [21] and [22]. In the recent study of Jin et al., no association between MET CNG and three most common genetic alterations (EGFR and KRAS activating mutations and ALK rearrangements) in lung ADCs was found. Only stage I Korean patients had been included into the study resulting in much higher proportion of nonsmokers and women in the patients’ cohort and higher incidence of EGFR mutations compared to our study [17]. The relations between MET and EGFR alterations are of a great clinical importance in the light of the hypothesis that increased MET dosage might lead to the primary resistance of NSCLCs with EGFR mutations to EGFR TKIs [12], as has been demonstrated for the acquired resistance in approximately 20% of patients with NSCLC [10] and [11].