Loss of either RASSF1A alone or in combination with Caveolin-1 inhibition is associated with different premalignant histopathological alterations in the mammary glands of transgenic mice

Analyses of human breast carcinomas (BCs) and premalignant breast lesions show that the loss of RASSF1A is an early event in the development of ER+ BCs, which correlates linearly with malignant progression. This observation suggests that RASSF1A inhibition is important for the development and progression of ER+ BCs. In addition to RASSF1A, concurrent caveolin-1 (Cav-1) inhibition may further promote ER+ breast carcinogenesis. In the present study, transgenic Rassf1a-/- and Cav-1(-/-) single as well as Rassf1a-/-, Cav-1(-/-) double knockout mice were used to investigate the impact of single or combined Rassf1a and Cav-1 inactivation on BC initiation. Loss of either one or both proteins led to different, pre-malignant histopathological alterations within the mammary glands of the mice, but not to fully developed BC, confirming that Rassf1a and Cav-1 are both important for maintaining the integrity of mammary gland epithelial structure, but suggesting that further intracellular changes or extracellular factors are required for the development of luminal BC when both genes are lost.