Malignant Potential Mechanisms And EGFR、KRAS Mutation In Pulmonary Micropapillary Adenocarcinoma

Objective:Pulmonary adenocarcinoma with a micropapillary pattern (MPPAC) is an aggressive subset of lung adenocarcinoma with poor prognosis. According to the new diagnostic criteria for the classification of lung adenocarcinoma (published in2011), whether it contains micropapillary pattern (MPP) we divided144cases of lung adenocarcinoma into two groups:MPP-positive and MPP-negative groups. The expression of Vimentin、E-cadherin、capase-3、pEGFR in specimens of120pulmonary adenocarcinoma tissue were determind by immunohistochemical assay. This study is to examine the characteristic of epithelial-mesenchymal transition (EMT) and prolification apoptosis in MPPAC. Provide theoretical basis for the clinical evaulation of its malignant potential. Furthermore, real time polymerase chain reaction (RT-PCR) method was used to detect the EGFR and KRAS gene mutations in specimens of144pulmonary adenocarcinoma frozen tumor tissue, to assess the correlation of MPPAC with EGFR and KRAS mutation status and determine their clinicopathological features.Methods:1. We choose144lung adenocarcinoma treated in Tianjin cancer hospital from Febtuary2009to October2012. All these cases have completed clinicopathological material and received surgical operaction. We divided144cases of lung adenocarcinoma into two groups according to the new diagnostic criteria for the classification of lung adenocarcinoma (published in2011):MPP-positive group and MPP-negative group. The MPP-positive group was further subdivided into three subgroups (+,++, and+++) according to the proportion of the micropapillary component.2. The expression of Vimentin、E-cadherin、capase-3、pEGFR in specimens of120pulmonary adenocarcinoma tissue were determind by immunohistochemical assay.3. Real time polymerase chain reaction (RT-PCR) method was used to detect the EGFR and KRAS gene mutations in specimens of144pulmonary adenocarcinoma frozen tumor tissue. Results:1. Results of immunohistochemical1.1The expression rates of Vimentin、E-cadherin、capase-3in120pulmonary adenocarcinoma tissue were20.8%、64.2%、70.0%, respectively. No significant correlation was found with expression of the three markers and patients’ gender、age、 smoking status、invasion、metastasis、tumor size and TNM stage (p>0.05). The expression rate of pEGFR was34.2%. Age、invasion、metastasis、tumor size and TNM stage did not show significant associations with pEGFR expression (p>0.05). pEGFR expression was higher in female (42.9%) than male (24.6%)(p=0.035), and also higher in nonsmoking patients (44.8%) than smoking patients (24.2%)(p=0.017).1.2Vimentin expression was higher in MPP-positive group (28.1%) than MPP-negative group (16.1%)(p=0.115) and mostly located in scatted cells in the MPP cavity; caspase-3expression was significantly higher in MPP-positive group (82.8%) than MPP-negative group (55.4%), p=0.001. The expression rate of E-cadherin in MPP-positive and negative group were62.5%、66.1%, p=0.684; and the expression rate of pEGFR in MPP-positive and negative group were34.4%、33.9%, p=0.959.2. Results of RT-PCR2.1Out of the144cases of lung adenocarcinoma,62cases (43.1%) have EGFR gene mutation while9cases (6.25%) have KRAS gene mutation. EGFR mutation is shown to be associated with gender (P=0.018) and tumor volume (P=0.016).2.2Among the clinicopathological factors:patients’ gender、age、smoking status、 invasion、metastasis、tumor size and TNM stage of MPP-positive and MPP-negative group were not statistically significant (p>0.05).2.3EGFR mutation was significantly higher in MPP-positive group (55.8%) than MPP-negative group (24.6%)(P<0.001), whereas KRAS mutation was lower in MPP-positive group (1.3%) than MPP-negative group (10.4%)(P=0.016).2.4EGFR mutation in MPP-poitive group is shown to be associated with tumor volume (P=0.002), but it was not to be associated with gender、age、smoking history、 invasion and P-TNM stage (p>0.05). 2.5Among the clinicopathological factors:patients’ gender、age、smoking status、 invasion、metastasis、tumor size and TNM stage of MPP-positive subgroups (+、++、+++) were not statistically significant (p>0.05).2.6EGFR mutation in MPP-positive subgroups (+、++、+++) were9(42.9%)、21(60.0%)、12(57.1%), respectively. No significant difference in the frequency of EGFR mutation among the three MPP-positive subgroups was indicated (P=0.932). KRAS mutation were too few to analysis.Conclusions:1. Scattered cells in the MPP cavity have a mesenchymal phenotype, which may favor invasion and metastasis.2. The expression of caspase-3is significantly higher in MPP-positive group than MPP-negative group (p=0.001), but it can not explain MPPAC with poor prognosis. The significance of caspase-3in development and clinical treatment of MPPAC need further study.3. pEGFR expression in120cases of lung adenocarcinoma was higher in female (p=0.035) and nonsmoking (p=0.017) patients. To a certain extent, pEGFR predict sensitivity to EGFR-TKIs.4. The frequency of EGFR mutation in MPPAC is higher compared with that in the other subtypes of lung adenocarcinoma. The frequency of KRAS mutation in MPPAC is lower compared with that in other subtypes of lung adenocarcinoma. There results indicate its unque molecular biological characteristic.5. The proportion of MPP in MPPAC was unrelated with EGFR mutation.