[Lani]

cancer cell growth/survival/effects have been found to be due to various pathways being either upregulated (encouraged, turned up in volume) or supressed. There are various feedback loops involved so turning one pathway up may turn another up as well, and yet another down. In other words, things are interrelated.

Cancer can escape blocking one pathway or route by substituting another route to allow it to grow, spread, etc.

In this study starving the her2+er+ tumor (and in some patients the her2-ER+ tumors) of estrogen by using an AI, just caused the cancer cell to increase its usage (upregulate ) of the alternate pathway, in this case the her2 pathway in order to continue to grow, thrive and spread.

This article brings into question whether alternative and/or additional drugs should be given to prevent this escape before it happens ie, faslodex instead of AIs (which may or may not work) or a HSP90 inhibitor which affects both her2 and ER from what I understand.

Hope this helps