Proteins belonging to the family caveolin microdomains are major components of cell membranes called kaweolami. Several studies suggest that caveolin-1 inhibits neoplastic transformation. The reduction or absence of expression of caveolin-1 appears to play an important role in the transformation of normal cells into cancer. However, the acquisition of the malignant phenotype of cancer cells seems to be accompanied by increased levels of caveolin-1. This suggests that abnormal expression of caveolin-1 are involved in both tumor formation and progression of cancer.