In vivo expression of the whole HOX gene network in human breast cancer.

The HOX network contains 39 genes that act as transcriptional regulators and control crucial cellular functions during both embryonic development and adult life. Inside the network, this is achieved according to the rules of temporal and spatial co-linearity with 3' HOX genes acting on the anterior part of the body, central HOX genes on the thoracic part and lumbo-sacral HOX genes on the caudal region. We analysed HOX gene expression in normal breast tissue and in primary breast cancers by reverse-transcriptase-polymerase chain reaction (RT-PCR). 17 out of 39 HOX genes were expressed in the normal breast tissue. The expression of thoracic HOX genes tended to be similar in normal and neoplastic breast tissues suggesting that these genes are involved in breast organogenesis. In contrast, cervical and lumbo-sacral HOX gene expression was altered in the primary breast cancers with respect to normal breast tissue. This supports their involvement in breast cancer evolution and suggests they could be targets for future cancer therapies.