Gene Therapy (2002) 9, 1338–1341  2002 Nature Publishing Group All rights reserved 0969-7128/02 $25.00 www.nature.com/gt BRIEF COMMUNICATION Combined effects on tumor growth and metastasis by anti-estrogenic and antiangiogenic therapies in MMTV- neu mice MG Sacco 1 , S Soldati 1,2 , E Mira Cato ´ 1 , L Cattaneo 1,3 , G Pratesi 4 , E Scanziani 2 and P Vezzoni 1 1 Department of Human Genome and Multifactorial Diseases, Istituto di Tecnologie Biomediche, ITB-CNR, Milan, Italy; 2 Istituto di Anatomia Patologica Veterinaria e Patologia Aviare, University of Milan, Milan, Italy; 3 Laboratory of Cell Therapy, Poliambulanza Hospital, Brescia, Italy; and 4 Istituto Nazionale Tumori, Milan, Italy Breast tumor growth and metastasization are both hormone- sensitive and angiogenesis-dependent. Recent work carried out in our laboratory on a transgenic model of breast cancer displaying many similarities to its human counterpart, has shown that liposome-mediated angiostatin cDNA delivery partially inhibits both local and metastatic growth. However, it is now recognized that anti-angiogenesis strategy alone cannot completely arrest tumor growth and spread, and this led to the suggestion that approaches based on different molecular mechanisms could usefully be combined. In the present work, we investigated whether tamoxifen, a classical antiestrogen agent widely used in human therapy, could Keywords: MMTVneu; transgenic mice; breast tumors; angiostatin; tamoxifen Breast cancer in women is a major health problem, caus- ing a great deal of suffering and a high number of deaths. So far, early diagnosis followed by surgery is the only way to cure the disease, while therapeutic protocols for women at an advanced stage of the disease are still unsat- isfactory and, in the long term, metastatic breast cancer is still associated with high treatment failure. 1 In humans, both chemotherapy and hormonal approaches for the management of the advanced disease are of great clinical relevance. Various drugs, including taxol, are active against disseminated breast cancer. 2 In addition, in patients with estrogen receptor positive tumors, antiestrogens, and tamoxifen in particular, have been widely used. 3 Many randomized trials have shown that postsurgical tamoxifen (TAM) treatment signifi- cantly reduces the growth of hormone receptor-positive breast cancer. Recently, the efficacy of TAM for chemo- prevention of breast tumors has been evaluated, and the data from the Breast Cancer Prevention Trial have dem- onstrated that TAM administration reduces the incidence of estrogen receptor-positive, but not receptor-negative tumors. 4,5 More recently, inhibition of tumor angiogenesis was investigated as a therapeutic strategy that can inhibit Correspondence: MG Sacco, CNR-ITB, Via Fratelli Cervi, 93, 20090 Segrate (MI), Italy Received 2 May 2002; accepted 23 May 2002 improve the results obtained with angiostatin alone. Further reduction of local growth was achieved with the combined regimen with respect to angiostatin or tamoxifen alone, while, as expected, no metastatic growth was detected in either group. We therefore conclude that a combination of angiogenesis inhibitors with antiestrogen drugs might be useful in humans and that other associations between con- ventional and gene transfer-mediated therapy are worth investigating and will soon become important components of anticancer therapy. Gene Therapy (2002) 9, 1338–1341. doi:10.1038/sj.gt.3301817 tumor growth and metastases. 6–9 Both the hormonal and chemotherapic approaches could, in theory, complement anti-angiogenic therapy, as their antitumoral action is mediated by different mechanisms. As recently recog- nized, to be of use to humans, any new therapeutic approach in experimental animals must be evaluated with regard to its ability to interfere with tumor metastas- ization, a goal rarely, if ever, investigated at the experimental level. To meet this fundamental requirement, over the last few years we have been validating an animal model of breast cancer, based on rat neu oncogene overexpression in mammary gland (MMTV-neu mouse), which matches to some extent its human counterpart, including the ability to give rise to distant metastases. 6,7,10 We have tested various gene therapy approaches to the treatment of breast cancer in this model, including the suicide, anti- sense and immune stimulating strategies. 10–13 We have shown that the results obtained in this model are more representative of what happens in the human pathology than those obtained with transplantable cultured tumoral cells injected in the immunocompromised host. More recently, by using this model, we have been able to show that liposome-mediated angiostatin gene delivery sig- nificantly reduces local tumor growth and abolishes its metastatic spread to lungs. 6,7 With the aim of implementing therapy protocols which could easily be translated to the human situation, and taking into consideration that tumors arising in our