Targeting CXCL1 chemokine signaling for treating cisplatin ototoxicity.

Cisplatin is chemotherapy used for solid tumor treatment like lung, bladder, head and neck, ovarian and testicular cancers. However, cisplatin-induced ototoxicity limits the utility of this agent in cancer patients, especially when dose escalations are needed. Ototoxicity is associated with cochlear cell death through DNA damage, the generation of reactive oxygen species (ROS) and the consequent activation of caspase, glutamate excitotoxicity, inflammation, apoptosis and/or necrosis. Previous studies have demonstrated a role of CXC chemokines in cisplatin ototoxicity. In this study, we investigated the role of CXCL1, a cytokine which increased in the serum and cochlea by 24 h following cisplatin administration. Adult male Wistar rats treated with cisplatin demonstrated significant hearing loss, assessed by auditory brainstem responses (ABRs), hair cell loss and loss of ribbon synapse. Immunohistochemical studies evaluated the levels of CXCL1 along with increased presence of CD68 and CD45-positive immune cells in cochlea. Increases in CXCL1 was time-dependent in the spiral ganglion neurons and organ of Corti and was associated with progressive increases in CD45, CD68 and IBA1-positive immune cells. Trans-tympanic administration of SB225002, a chemical inhibitor of CXCR2 (receptor target for CXCL1) reduced immune cell migration, protected against cisplatin-induced hearing loss and preserved hair cell integrity. We show that SB225002 reduced the expression of CXCL1, NOX3, iNOS, TNF-α, IL-6 and COX-2. Similarly, knockdown of CXCR2 by trans-tympanic administration of CXCR2 siRNA protected against hearing loss and loss of outer hair cells and reduced ribbon synapses. In addition, SB225002 reduced the expression of inflammatory mediators induced by cisplatin. These results implicate the CXCL1 chemokine as an early player in cisplatin ototoxicity, possibly by initiating the immune cascade, and indicate that CXCR2 is a relevant target for treating cisplatin ototoxicity.

Tonic suppression of PCAT29 by the IL-6 signaling pathway in prostate cancer: Reversal by resveratrol.

Prostate cancer (PCa) is the second leading cause of cancer deaths in men. A better understanding of the molecular basis of prostate cancer proliferation and metastasis should enable development of more effective treatments. In this study we focused on the lncRNA, prostate cancer associated transcript 29 (PCAT29), a putative tumor suppressive gene. Our data show that the expression of PCAT29 was reduced in prostate cancer tumors compared to paired perinormal prostate tissues. We also observed substantially lower levels of PCAT29 in DU145 and LNCaP cells compared to normal prostate (RWPE-1) cells. IL-6, a cytokine which is elevated in prostate tumors, reduced the expression of PCAT29 in both DU145 and LNCaP cells by activating signal transducer and activator of transcription 3 (STAT3). One downstream target of STAT3 is microRNA (miR)-21, inhibition of which enhanced basal PCAT29 expression. In addition, we show that resveratrol is a potent stimulator of PCAT29 expression under basal condition and reversed the down regulation of this lncRNA by IL-6. Furthermore, we show that knock down of PCAT29 expression by siRNA in DU145 and LNCaP cells increased cell viability while increasing PCAT29 expression with resveratrol decreased cell viability. Immunohistochemistry studies showed increased levels of STAT3 and IL-6, but low levels of programmed cell death protein 4 (PDCD4), in prostate tumor epithelial cells compared to adjacent perinormal prostate epithelial cells. These data show that the IL-6/STAT3/miR-21 pathway mediates tonic suppression of PCAT29 expression and function. Inhibition of this signaling pathway by resveratrol induces PCAT29 expression and tumor suppressor function.