TLR4 is a novel determinant of the response to paclitaxel in breast cancer
Menée in vitro et in vivo, cette étude met en évidence le rôle joué par la surexpression du récepteur TLR4 dans la réponse au paclitaxel d'un cancer du sein
Overexpression of Toll-like Receptor-4 (TLR4) in human tumors often correlates with chemoresistance and metastasis. We found that TLR4 is overexpressed in the majority of clinical breast cancer (BC) samples and in 68% of the examined BC lines. TLR4 is activated by lipopolysaccharide (LPS) and other ligands including the widely-used drug paclitaxel (PXL). LPS is frequently used to show a tumor-promoting role of TLR4 although this bacterial component is unlikely to be found in BC environment. We reasoned that PXL-dependent activation of TLR4 is more relevant to BC chemoresistance that could be mediated by activation of the NF-κB pathway leading to upregulation of pro-survival genes. To test this hypothesis, we correlated TLR4 expression with resistance to PXL in two modified BC lines with either depleted or overexpressed TLR4 protein. Depletion of TLR4 in naturally overexpressing MDA-MB-231 cells downregulated pro-survival genes concomitant with 2-3 fold reduced IC50 to PXL in vitro and a 6-fold decrease in recurrence rate in vivo. Conversely, TLR4 overexpression in a negative cell line HCC1806 significantly increased expression of inflammatory and pro-survival genes along with a 3-fold increase of IC50 to PXL in vitro and enhanced tumor resistance to PXL therapy in vivo. Importantly, both tumor models showed that many PXL-upregulated inflammatory cytokines were co-induced with their receptors suggesting that this therapy induces autocrine tumor-promoting loops. Collectively, these results demonstrate that paclitaxel not only kills tumor cells but also enhances their survival by activating TLR4 pathway. These findings suggest that blocking TLR4 could significantly improve response to chemotherapy.
http://mct.aacrjournals.org/content/early/2013/05/24/1535-7163.MCT-12-1019.abstract