The miR-200 family is well known to inhibit the epithelial–mesenchymal transition, suggesting it may therapeutically inhibit metastatic biology. However, conflicting reports regarding the role of miR-200 in suppressing or promoting metastasis in different cancer types have left unanswered questions. Here we demonstrate a difference in clinical outcome based on miR-200’s role in blocking tumour angiogenesis. We demonstrate that miR-200 inhibits angiogenesis through direct and indirect mechanisms by targeting interleukin-8 and CXCL1 secreted by the tumour endothelial and cancer cells. Using several experimental models, we demonstrate the therapeutic potential of miR-200 delivery in ovarian, lung, renal and basal-like breast cancers by inhibiting angiogenesis. Delivery of miR-200 members into the tumour endothelium resulted in marked reductions in metastasis and angiogenesis, and induced vascular normalization. The role of miR-200 in blocking cancer angiogenesis in a cancer-dependent context defines its utility as a potential therapeutic agent.

Purpose: The oncogenic miR-155 is upregulated in many human cancers, and its expression is increased in more aggressive and therapy-resistant tumors, but the molecular mechanisms underlying miR-155-induced therapy resistance are not fully understood. The main objectives of this study were to determine the role of miR-155 in resistance to chemotherapy and to evaluate anti-miR-155 treatment to chemosensitize tumors. Experimental Design: We performed in vitro studies on cell lines to investigate the role of miR-155 in therapy resistance. To assess the effects of miR-155 inhibition on chemoresistance, we used an in vivo orthotopic lung cancer model of athymic nude mice, which we treated with anti-miR-155 alone or in combination with chemotherapy. To analyze the association of miR-155 expression and the combination of miR-155 and TP53 expression with cancer survival, we studied 956 patients with lung cancer, chronic lymphocytic leukemia, and acute lymphoblastic leukemia. Results: We demonstrate that miR-155 induces resistance to multiple chemotherapeutic agents in vitro, and that downregulation of miR-155 successfully resensitizes tumors to chemotherapy in vivo. We show that anti-miR-155-DOPC can be considered non-toxic in vivo. We further demonstrate that miR-155 and TP53 are linked in a negative feedback mechanism and that a combination of high expression of miR-155 and low expression of TP53 is significantly associated with shorter survival in lung cancer. Conclusions: Our findings support the existence of an miR-155/TP53 feedback loop, which is involved in resistance to chemotherapy and which can be specifically targeted to overcome drug resistance, an important cause of cancer-related death. Clin Cancer Res; 23(11); 2891–904. ©2016 AACR.

Adrenergic regulation of monocyte chemotactic protein 1 leads to enhanced macrophage recruitment and ovarian carcinoma growth Adrenergic regulation of monocyte chemotactic protein 1 leads to enhanced macrophage recruitment and ovarian carcinoma growth

Purpose: RNA interference has the potential to specifically knockdown the expression of target genes and thereby transform cancer therapy. However, lack of effective delivery of siRNA has dramatically limited its in vivo applications. We have developed a multistage vector (MSV) system, composed of discoidal porous silicon particles loaded with nanotherapeutics, that directs effective delivery and sustained release of siRNA in tumor tissues. In this study, we evaluated therapeutic efficacy of MSV-loaded EphA2 siRNA (MSV/EphA2) with murine orthotopic models of metastatic ovarian cancers as a first step toward development of a new class of nanotherapeutics for the treatment of ovarian cancer. Experimental Design: Tumor accumulation of MSV/EphA2 and sustained release of siRNA from MSV were analyzed after intravenous administration of MSV/siRNA. Nude mice with metastatic SKOV3ip2 tumors were treated with MSV/EphA2 and paclitaxel, and therapeutic efficacy was assessed. Mice with chemotherapy-resistant HeyA8 ovarian tumors were treated with a combination of MSV/EphA2 and docetaxel, and enhanced therapeutic efficacy was evaluated. Results: Treatment of SKOV3ip2 tumor mice with MSV/EphA2 biweekly for 6 weeks resulted in dose-dependent (5, 10, and 15 μg/mice) reduction of tumor weight (36%, 64%, and 83%) and number of tumor nodules compared with the control groups. In addition, tumor growth was completely inhibited when mice were treated with MSV/EphA2 in combination with paclitaxel. Furthermore, combination treatment with MSV/EphA2 and docetaxel inhibited growth of HeyA8-MDR tumors, which were otherwise resistant to docetaxel treatment. Conclusion: These findings indicate that MSV/EphA2 merits further development as a novel therapeutic agent for ovarian cancer. Clin Cancer Res; 19(7); 1806–15. ©2013 AACR.

Despite being among the most common oncogenes in human cancer, to date, there are no effective clinical options for inhibiting KRAS activity. We investigated whether systemically delivered KRAS siRNAs have therapeutic potential in KRAS-mutated cancer models. We identified KRAS siRNA sequences with notable potency in knocking down KRAS expression. Using lung and colon adenocarcinoma cell lines, we assessed antiproliferative effects of KRAS silencing in vitro. For in vivo experiments, we used a nanoliposomal delivery platform, DOPC, for systemic delivery of siRNAs. Various lung and colon cancer models were used to determine efficacy of systemic KRAS siRNA based on tumor growth, development of metastasis, and downstream signaling. KRAS siRNA sequences induced >90% knockdown of KRAS expression, significantly reducing viability in mutant cell lines. In the lung cancer model, KRAS siRNA treatment demonstrated significant reductions in primary tumor growth and distant metastatic disease, while the addition of CDDP was not additive. Significant reductions in Ki-67 indices were seen in all treatment groups, whereas significant increases in caspase-3 activity were only seen in the CDDP treatment groups. In the colon cancer model, KRAS siRNA reduced tumor KRAS and pERK expression. KRAS siRNAs significantly reduced HCP1 subcutaneous tumor growth, as well as outgrowth of liver metastases. Our studies demonstrate a proof-of-concept approach to therapeutic KRAS targeting using nanoparticle delivery of siRNA. This study highlights the potential translational impact of therapeutic RNA interference, which may have broad applications in oncology, especially for traditional “undruggable” targets. Mol Cancer Ther; 13(12); 2876–85. ©2014 AACR.

Purpose: VEGF-targeted therapies have modest efficacy in cancer patients, but acquired resistance is common. The mechanisms underlying such resistance are poorly understood. Experimental Design: To evaluate the potential role of immune cells in the development of resistance to VEGF blockade, we first established a preclinical model of adaptive resistance to anti-VEGF therapy. Additional in vitro and in vivo studies were carried out to characterize the role of macrophages in such resistance. Results: Using murine cancer models of adaptive resistance to anti-VEGF antibody (AVA), we found a previously unrecognized role of macrophages in such resistance. Macrophages were actively recruited to the tumor microenvironment and were responsible for the emergence of AVA resistance. Depletion of macrophages following emergence of resistance halted tumor growth and prolonged survival of tumor-bearing mice. In a macrophage-deficient mouse model, resistance to AVA failed to develop, but could be induced by injection of macrophages. Downregulation of macrophage VEGFR-1 and VEGFR-3 expression accompanied upregulation of alternative angiogenic pathways, facilitating escape from anti-VEGF therapy. Conclusions: These findings provide a new understanding of the mechanisms underlying the modest efficacy of current antiangiogenesis therapies and identify new opportunities for combination approaches for ovarian and other cancers. Clin Cancer Res; 23(22); 7034–46. ©2017 AACR.