Guest Blog Post: What Causes Breast Cancer?

Dr. James Holland is the Distinguished Professor of Neoplastic Diseases at the Icahn School of Medicine at Mount Sinai and his leadership is instrumental in the development of the T.J. Martell Memorial Laboratories in the Icahn School of Medicine at Mount Sinai.

Although there has been wonderful progress in diagnosing breast cancer in the last 35 years using physical exam, sonography, mammography and magnetic resonance imaging, and in surgery, substituting lumpectomy for radical mastectomy, and sentinel node biopsy for wide dissection, and in radiation therapy, hormone therapy, chemotherapy and immunotherapy, so that the majority of women are now cured of this common disease,  little research has been done on finding one or more causes that makes this disease so common.

Recognized inherited genetic factors account for less than 10% of cases. The T.J. Martell Memorial Laboratories in the Icahn School of Medicine at Mount Sinai has a deep program exploring a viral cause for human breast cancer. Breast cancer in mice is known to be caused by a mammary tumor virus (MMTV).  We have found a virus 90 to 95% identical to MMTV which we have named HMTV, in 40% of the breast cancers in American women.  We can infect other cells with it, indicating HMTV is alive and active.  It is not in the normal tissues of the patient, thus excluding genetic inheritance, but rather is acquired after birth.  The distribution of the virus in breast cancers around the world (high in the USA, low in China for example) parallels the content of MMTV in the different species of mice which varies widely.

The work will continue until we provide rock solid proof that HMTV causes human breast cancer, which then opens up new means of prevention and therapy.  And none of this would have happened without Martell Foundation support.