Targeting FOXP3 Tumor-Intrinsic Effects Using Adenoviral Vectors in Experimental Breast Cancer

Abstract

The regulatory T cell master transcription factor, Forkhead box P3 (Foxp3), has been detected in cancer cells; however, its role in breast tumor pathogenesis remains controversial. Here we assessed Foxp3 tumor intrinsic effects in experimental breast cancer using a Foxp3 binder peptide (P60) that impairs Foxp3 nuclear translocation. Cisplatin upregulated Foxp3 expression in HER2+ and triple-negative breast cancer (TNBC) cells. Foxp3 inhibition with P60 enhanced chemosensitivity and reduced cell survival and migration in human and murine breast tumor cells. We also developed an adenoviral vector encoding P60 (Ad.P60) that efficiently transduced breast tumor cells, reduced cell viability and migration, and improved the cytotoxic response to cisplatin. Conditioned medium from transduced breast tumor cells contained lower levels of IL-10 and improved the activation of splenic lymphocytes. Intratumoral administration of Ad.P60 in breast-tumor-bearing mice significantly reduced tumor infiltration of Tregs, delayed tumor growth, and inhibited the development of spontaneous lung metastases. Our results suggest that Foxp3 exerts protumoral intrinsic effects in breast cancer cells and that gene-therapy-mediated blockade of Foxp3 could constitute a therapeutic strategy to improve the response of these tumors to standard treatment.

Intratumoral delivery of immunotherapy to treat breast cancer: current development in clinical and preclinical studies

“…Expression of the transcription factor Foxp3 in both Tregs and in BC cells was targeted with a cell penetrating peptide P60 that binds to a region of Foxp3 encoded in an adenoviral vector ( 99 ). When HER2+ LM3 and TNBC E0771 mouse tumors reached a burden of 500 mm 3 , the vector was delivered once every three days for a total of three treatments, leading to tumor growth delay and decreased lung metastases.…”

“…When HER2+ LM3 and TNBC E0771 mouse tumors reached a burden of 500 mm 3 , the vector was delivered once every three days for a total of three treatments, leading to tumor growth delay and decreased lung metastases. Treatment led to a reduction of Tregs in the tumor but not the spleen ( 99 ).…”

“…Anti-tumor effects in un-injected, abscopal tumors were observed with the adenovirus Ad-RTA-hIL-12 ( 51 ), and adenovirus CAdVEC ( 60 , 61 ) in clinical studies. Preclinical treatments with antibodies, cells, viruses, cytokines, and innate immune agonists reduced or eliminated metastases ( 72 , 75 – 77 , 92 , 94 , 99 , 100 , 110 , 118 , 120 , 121 , 127 , 129 , 132 , 135 , 136 , 138 , 140 , 145 ) and induced systemic anti-tumor effect in untreated tumors ( 79 , 119 , 130 , 131 , 133 – 135 ). Furthermore, i.t.…”