The formation of acellular capillaries in the retina, a hallmark feature of diabetic retinopathy, is caused by apoptosis of endothelial cells and pericytes. The biochemical mechanism of such apoptosis remains unclear. Small heat shock proteins play an important role in the regulation of apoptosis. In the diabetic retina, pro-inflammatory cytokines are upregulated. In this study, we investigated the effects of pro-inflammatory cytokines on small heat shock protein 27 (Hsp27) in human retinal endothelial cells (HREC). In HREC cultured in the presence of cytokine mixtures (CM), a significant downregulation of Hsp27 at the protein and mRNA level occurred, with no effect on HSF-1, the transcription factor for Hsp27. The presence of high glucose (25 mM) amplified the effects of cytokines on Hsp27. CM activated indoleamine 2,3-dioxygenase (IDO) and enhanced the production of kynurenine and ROS. An inhibitor of IDO, 1-methyl tryptophan (MT), inhibited the effects of CM on Hsp27. CM also upregulated NOS2 and, consequently, nitric oxide (NO). A NOS inhibitor, L-NAME, and a ROS scavenger blocked the CM-mediated Hsp27 downregulation. While a NO donor in the culture medium did not decrease the Hsp27 content, a peroxynitrite donor and exogenous peroxynitrite did. The cytokines and high glucose-induced apoptosis of HREC were inhibited by MT and L-NAME. Downregulation of Hsp27 by a siRNA treatment promoted apoptosis in HREC. Together, these data suggest that pro-inflammatory cytokines induce the formation of ROS and NO, which, through the formation of peroxynitrite, reduce the Hsp27 content and bring about apoptosis of retinal capillary endothelial cells.

High-mobility group box 1 (HMGB1) is a dynamic nuclear protein participating in transcription, chromatin remodelling, and DNA recombination and repair processes. Accumulating evidence indicates that its function now extends beyond the nucleus, notably its extracellular role in inflammation. HMGB1 is implicated as a late mediator of sepsis and is also believed to promote atherosclerosis and other inflammatory diseases such as rheumatoid arthritis and systemic lupus erythematosus. Interestingly, deregulation of HMGB1 is shown to be associated with the hallmarks of cancer development. Moreover, several clinical studies have shown that HMGB1 is a promising biomarker for a variety of cancer types. In this review, we provide novel insights into the role and mechanisms of HMGB1, in particular, to hormone-related cancers and its potential to serve as a therapeutic target.

Phosphatase of Regenerating Liver 3 (PRL-3) has recently been demonstrated to play a role in the cellular processes associated with cancer metastasis and has been suggested as a potential new target for cancer therapies. Several pre-clinical evaluations targeting PRL-3 have shown great promise for cancer treatment. Statins are a class of drugs that inhibit 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR) and have been shown to have anti-cancer properties in a variety of cancer types including prostate cancer (PC); previous work has shown that one of the anti-cancer effects of statins is the inhibition of protein prenylation, a post translational modification that allows proteins to associate with the plasma membrane. Prenylation of PRL-3 plays a critical role in cell membrane localization and metastatic process; therefore, targeting PLR-3 prenlyation may be an attractive strategy. In our recent work, we have identified that PRL-3 is highly expressed in aggressive prostate cancer cells and is critical for the motility behavior. Our hypothesis is that lovastatin treatment will reduce the metastatic properties of PC cells by inhibiting prenylation of PRL-3 and therefore reduce the oncogenic effects of the PRL-3 cascade of events required for PC metastasis. Advanced PC cell line, DU145 was used in this study to characterize PRL-3 function. Cell viability assays showed that lovastatin has dose dependent effects on DU145. Western Blot analysis was then used to analyze expression levels of PRL-3 and its downstream proteins in DU145 cells treated with lovastatin. Cellular localization of PRL-3 following lovastatin treatments was also conducted using Western blot analysis. Following this, migration assays were performed using Boyden chamber to determine whether lovastatin has anti-migration effects in PC cells. Immunoprecipitation (IP) analyses were also performed to determine whether PRL-3 and Translationally Controlled Tumor Protein (TCTP) [a mediator of PRL-3 function] are binding partners using respective antibodies. Our studies have shown lovastatin decreases the expression of PRL-3 resulting in the inhibition of DU145 cell proliferation; furthermore, a reduction in TCTP expression has also been observed in treated cells versus control cells. Specifically, lovastatin decreases the membrane localization of both PRL-3 and TCTP in DU145 cells. Moreover, IP results show that PRL-3 and TCTP are potential binding partners and this interaction may be critical for PC metastasis. Finally our results show that lovastatin has the ability to decrease the motility of DU145 PC cells in vitro. Taken together, our results for the first time show that lovastatin can target PRL-3 by interfering with prenylation and preventing the membrane location of PRL-3 and its downstream effector, TCTP in advanced prostate cancer cells. Targeting PRL-3 warrants further studies to develop PRL-3 as a therapeutic target for PC. Citation Format: Allison K. Palmer, Gnanasekar Munirathinam. Effects of lovastatin on the PRL-3 cascade of events in prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1766. doi:10.1158/1538-7445.AM2015-1766