The Molecular Biology of Pulmonary Metastasis

The majority of deaths from cancer result not from growth of the original primary tumor, but rather from the growth of metastatic disease. For cancer to spread from the primary site, neoplastic cells must undertake a complex multi-step process. The molecular steps involved in this process have been the subject of intense study for a number of years, and they are now beginning to be elucidated. Moreover, inhibitors of the processes involved in metastasis are in various stages of development, with the hope of molecularly targeting a neoplastic cell's ability to disseminate. The lungs have long been known to be one of the most common sites of metastasis. Initially presumed to be determined by blood flow and oxygen tension, targeting of the lungs by metastatic cancer cells is now known to be a non-random molecularly derived event. This review presents our current understanding of the processes involved in the development of pulmonary metastasis from the genetic imprint of the "metastatic signature" to the steps involved in the "metastatic cascade.".