细支气管肺泡癌的分子生物学研究

Molecular biological features of bronchioloalveolar carcinoma

目的细支气管肺泡癌(BAC)发病率呈明显上升趋势,靶向药物已成为BAC治疗热点。本文探索BAC分子生物学特点,包括EGFR-TK结构域的突变、EGFR和HER2的基因拷贝数和蛋白表达,以便探讨它们与BAC的治疗反应及预后关系。方法采用PCR和DNA测序法检测中国人BAC石蜡包埋组织标本EGFR基因突变情况;EGFR试剂盒检测BAC患者外周血EGFR基因突变;荧光原位杂交法(FISH)及免疫组织化学法(IHC)分别检测组织标本中癌细胞的EGFR和HER2基因拷贝数和蛋白表达。结果 BAC组织标本中EGFR基因突变率50%(16/32),其中主要为L858R(50%)及外显子19缺失突变(43.8%)。EGFR基因拷贝数增加的阳性率41.2%(14/34)。EGFR蛋白表达阳性率76.5%(26/34)。HER2基因拷贝数增加/基因扩增阳性率5.7%(2/35)及蛋白表达阳性率6.1%(2/34),其中2例均为EGFR/HER2共表达。8例外周血EGFR检测有5例(62.5%)EGFR基因突变。研究显示仅EGFR基因拷贝数与EGFR基因突变率有非常显著的相关性(P=0.001)。与性别、吸烟情况、BAC病理亚型、EGFR蛋白表达没有显著相关性。结论 BAC具有较高的EGFR基因突变率、EGFR基因拷贝数增加的阳性率和蛋白表达阳性率。少数可能具有EGFR/HER2的共表达。鉴于EGFR突变阳性率高,测定方法便捷,因此是BAC靶向治疗依据的主要检测目标。外周血游离DNA中的EGFR突变检测值得进一步探讨。

Objective Bronchioloalveolar carcinoma （BAC） is a subtype of puhnonary adenocarcinoma. Recent data have suggested an increase in the incidence of BAC. This study is intended to evaluate EGFR mutation, gene copy number, and protein expression of both EGFR and HER2 in BAC, and to investigate their relationship with treatment response and prognosis of BAC. Methods EGFR mutations in the paraffin-embedded BAC samples were analyzed by PCR and DNA sequencing. EGFR mutations in the peripheral blood of BAC patients were analyzed by PCR and EGFR mutation test kit. Gene copy number and protein expression of EGFR and HER2 in the paraffin-embedded BAC samples were evaluated by FISH and IHC, respectively. Results EGFR mutations were detected in 50% （16/32） of BAC samples. A- mong them, 7 cases （43.8%） were exon 19 deletions and 8 cases （50%） were L858R. EGFR mutations in peripheralblood were detected in 5 out of 8 cases （62.5%） ; in addition, 14 out of 34 cases （41.2%） were fouml to have in- creased EGFR gene copy numbers, 26 out of 34 cases （76. 5% ） were found to have positive EGFR protein expression, and 2 cases demonstrated both increased HER2 gene copy number/gene amplification and positive HER2 expression. EGFR mutation was signifieantly correlated with EGFR gene copy number （P = 0. 001 ）. Conclusion BAC has relatively high incidence of EGFR-TKI sensitive mutation, increased EGFR gene copy number, positive protein expression, and possibly EGFR/HER2 co-expression. This may indirectly explain the better treatment response of EGFR-TKIs in BAC patients. EGFR multation versus increased EGFR gene copy number detected is more convenient and highly sensitive. Testing free DNA in the peripheral blood for EGFR mutations ,nay help predict the responses of ECFR-TKIs in BAC patients.