Caveolin-1 expression in lung carcinoma varies according to tumour histotype and is acquired de novo in brain metastases

Aims:  To study caveolin-1 (Cav-1) expression in metastatic lung carcinomas.
Methods and results:  Cav-1 expression was investigated in a series of 121 lung carcinomas and it was shown that 18/121 tumours (14.9%) were Cav-1+. None of the pure bronchioloalveolar carcinomas proved to be positive, vs. 42.8% of the large cell carcinomas (neuroendocrine subtype excluded). Adenocarcinomas (8.5%), large cell neuroendocrine carcinomas (20%) and squamous cell carcinomas (29.6%) displayed an intermediate percentage of positive cases, suggesting a gradient of Cav-1 expression according to tumour histotype-related aggressiveness. Moreover, the percentage of Cav-1+ tumours with distant metastases was almost double that of non-metastatic tumours (17.8% vs. 8.1%), irrespective of the histotype. In 34 tumours metastatic to the brain, primary and secondary lesions were compared and 53% of brain metastases were Cav-1+ vs. 20.6% of primaries, indicating a de novo acquisition of Cav-1 expression. This pattern was exclusive to the brain, as it was not acquired in adrenal metastases. In our series, the presence of epidermal growth factor receptor amplification, determined by fluorescence in situ hybridization, was not related to Cav-1 reactivity.
Conclusions:  Cav-1 immunoreactivity in lung carcinoma is histotype-dependent and acquired de novo in brain metastases, suggesting a site-specific phenotypic shift in secondary lesions.