The effect of trastuzumab/docatexel combination on breast cancer angiogenesis: dichotomus effect predictable by the HIFI alpha/VEGF pre-treatment status?

In this study we describe and discuss the dichotomous effects of docetaxel trastuzumab (Herceptin)/docetaxel therapy on the angiogenic molecular profile in two patients with her-2 + chemo-resistant recurrent breast carcinoma. In the first case, an intensification of angiogenesis occurred following therapy, accompanied by an impressive increase of the cancer cell proliferation index. This tumor did not express HIF1 alpha and shared a HIF-independent VEGF overexpression, which remained unaffected by therapy. An intensified formation of thymidine phosphorylase (TP)-rich stroma, presumably a response to docetaxel, shows a TP-dependent angiogenic response. In the second patient, VEGF and HIF1 alpha were down-regulated in post-treatment biopsies and this was accompanied by a sharp reduction of the vascular density and of the cancer cell proliferation rate. In both cases, c-erbB-2 expression was abrogated by Herceptin. Taking into account that Herceptin down-regulates VEGF through reduction of HIF1 alpha synthesis, this clinical study provides evidence that an anti-angiogenic effect from Herceptin/Docetaxel therapy is expected only in tumors with HIF1 alpha-dependent VEGF overexpression. In contrast, HIF1 alpha-independent VEGF angiogenic activity cannot be abrogated by Herceptin. Docetaxel mediated up-regulation of TP in the tumoral stroma may, on the contrary, result in angiogenesis intersification and rapid tumor relapse. Such an effect should be of clinical importance since Herceptin/Docetaxel-based regimens are currently evaluated for the adjuvant therapy of her-2 + breast cancer patients. Studying the Herceptin-induced phenotypic changes of tumors could lead to the identification of specific molecular profiles that bring about diverging angiogenic responses. Adjustment of the chemotherapy regimen accordingly would prove of clinical importance.