Toll-like receptor-9 (TLR9) is a DNA receptor widely expressed in cancers. Although synthetic TLR9 ligands induce cancer cell invasion in vitro, the role of TLR9 in cancer pathophysiology is unclear. We discovered that low tumor TLR9 expression is associated with significantly shortened disease-specific survival in patients with triple negative but not with ER+ breast cancers. A likely mechanism of this clinical finding involves differential responses to hypoxia. Our pre-clinical studies indicate that while TLR9 expression is hypoxia-regulated, low TLR9 expression has different effects on triple negative and ER+ breast cancer invasion in hypoxia. Hypoxia-induced invasion is augmented by TLR9 siRNA in triple negative, but not in ER+ breast cancer cells. This is possibly due to differential TLR9-regulated TIMP-3 expression, which remains detectable in ER+ cells but disappears from triple-negative TLR9 siRNA cells in hypoxia. Our results demonstrate a novel role for this innate immunity receptor in cancer biology and suggest that TLR9 expression may be a novel marker for triple-negative breast cancer patients who are at a high risk of relapse. Furthermore, these results suggest that interventions or events, which induce hypoxia or down-regulate TLR9 expression in triple-negative breast cancer cells may actually induce their spread.

Purpose: An inherent problem in breast cancer treatment is that current therapeutic approaches fail to specifically target the dissemination of breast cancer cells from the primary tumor. Clinical findings show that the loss of Wnt-5a protein expression in the primary breast tumor predicts a faster tumor spread, and in vitro analyses reveal that it does so by inhibiting tumor cell migration. Therefore, we hypothesized that the reconstitution of Wnt-5a signaling could be a novel therapeutic strategy to inhibit breast cancer metastasis. Experimental Design: We used in vitro techniques to show that 4T1 mouse breast cancer cells responded to the reconstitution of Wnt-5a signaling using our novel Wnt-5a mimicking hexapeptide, Foxy-5, in the same way as human breast cancer cells. Therefore, we could subsequently study its effect in vivo on the metastatic spread of cancer following the inoculation of 4T1cells into mice. Results: In vitro analyses revealed that both recombinant Wnt-5a and the Wnt-5a^derived Foxy-5 peptide impaired migration and invasion without affecting apoptosis or proliferation of 4T1 breast cancer cells. The in vivo experiments show that i.p. injections of Foxy-5 inhibited metastasis of inoculated 4T1breast cancer cells from the mammary fat pad to the lungs and liver by 70% to 90%. Conclusions: These data provide proof of principle that the reconstitution of Wnt-5a signaling in breast cancer cells is a novel approach to impair breast tumor metastasis by targeting cell motility. In combination with existing therapies, this approach represents a potential novel therapeutic strategy for the treatment of breast cancer patients.Breast cancer is the most common malignancy among women, and it is predicted to afflict 1 in 10 females during their lifetime. The development of improved diagnostics and therapeutics for breast cancer had led to a reduction in overall mortality rates (1). However, tumor metastasis is the predominant cause of death among patients, and the 5-year survival remains less than 30% in patients with distal spread of their tumor (1).In this context, the nontransforming Wnt-5a protein seems to be a promising therapeutic candidate, as the lack of Wnt-5a protein expression in the primary tumor of breast cancer patients strongly correlates with an increased risk of metastasis and reduced survival (2, 3). This inhibitory effect of Wnt-5a on metastasis may be due to the ability of Wnt-5a to increase adhesion and thereby decrease migration of breast epithelial cells (4, 5), as well as to its ability to counteract activation of NFAT (6), a transcription factor that has been implicated in promoting breast cancer cell invasiveness (7,8). Indirect support for a suppressive effect of Wnt-5a on breast cancer cell migration comes from a recent and elegant study of mammary gland development (9). In this study the investigators clearly show that Wnt-5a signaling is capable of inhibiting ductal extension and lateral branching in the mammary gland most likely via an increased cell adhesion. A tumo...

BackgroundCyclin A1 is a cell cycle regulator that has been implicated in the progression of prostate cancer. Its role in invasion and metastasis of this disease has not been characterized.MethodsImmunohistochemistry and cDNA microarray analyses were used to assess protein and mRNA expression of cyclin A1 and proteins with roles in metastasis, including vascular endothelial growth factor (VEGF), metalloproteinase 2 (MMP2), and MMP9, in human prostate cancer. Transient transfection and infection with viral vectors expressing cyclin A1 and short hairpin RNA (shRNA) targeting cyclin A1 were used to study the effects of altered cyclin A1 expression in PC3 prostate cancer cells. The BrdU assay, annexin V staining, and invasion chambers were used to examine cyclin A1 effects on proliferation, apoptosis, and invasion, respectively. The role of cyclin A1 and androgen receptor (AR) in transcription of VEGF and MMP2 was assessed by promoter mutation and chromatin immunoprecipitation. The effect of cyclin A1 expression on tumor growth and metastasis was analyzed in a mouse model of metastasis. All statistical tests were two-sided.ResultsCyclin A1 protein and mRNA expression were statistically significantly higher in prostate cancers than in adjacent benign tissues. A statistically significant correlation between expression of cyclin A1 and of MMP2, MMP9, and VEGF was observed in prostate tumors from 482 patients (P values from Spearman rank correlation tests < .001). PC3 cells that overexpressed cyclin A1 showed increased invasiveness, and inhibition of cyclin A1 expression via shRNA expression reduced invasiveness of these cells. Eight of 10 mice (80%) bearing PC3 cells overexpressing cyclin A1 had infiltration of tumor cells in lymph node, liver, and lung, but all 10 mice bearing tumors expressing control vector were free of liver and lung metastases and only one mouse from this group had lymph node metastasis (P values from Fisher exact tests < .001). Cyclin A1, in concert with AR, bound to and increased expression from the VEGF and MMP2 promoters.ConclusionsCyclin A1 contributes to prostate cancer invasion by modulating the expression of MMPs and VEGF and by interacting with AR.