Background: Aberrant expression of Secretory Leukocyte Protease Inhibitor (SLPI) has been associated with human cancer growth and its suppression was identified as a potential target for anti-cancer drugs, particularly in colorectal cancer. However, the underlying mechanism by which SLPI affected the development of drug resistance in CRC remains unclear. Objective: This study investigated the role of SLPI in the p53-up-regulated modulator of apoptosis (PUMA)-mediated CRC cells’ apoptosis and their chemosensitivity to Cisplatin. Methods: A series of qRT-PCR and western blot analyses were performed to characterize the expressions of SLPI, PUMA, and Akt in CRC lines. Tunel, transwell, and CCK-8 analyses were monitored to define the impacts of the siRNA-mediated knockdown of SLPI on CRC cell development. Furthermore, in vivo development of CRC was evaluated in nude mice infected with siSLPI or Cisplatin alone or both, and Ki67 and caspase-3 immunohistochemistry assay was monitored on multiple tissue microarray from the same cohort. Results: Our results showed that SLPI inhibition strongly promoted the expressions of the pro-apoptotic protein PUMA, cleaved-caspase3 and Bax and reduced the cell viability of HT29 and HT116 cell lines in vitro. In addition, siSLPI knockdown effectively suppressed both Akt and FoxO3 proteins and improved the sensitivity to cisplatin chemotherapy. Xenograft tumor assay revealed a lowered growth in mice treated with Cisplatin, while combined treatment of siSLPI achieved more significant anticancer effects than Cisplatin alone. Conclusions: Taken together, these findings demonstrated that suppression of SLPI might repress the growth of human colorectal cancer cells both in vitro and in vivo. These results suggested SLPI as a novel resistance factor to Cisplatin, and a combination of Cisplatin and SLPI inhibitor be beneficial for colorectal cancer therapy.

The mechanism of colistin-induced neurotoxicity is still unknown. Our recent study (L. Zhang, Y. H. Zhao, W. J. Ding, G. Z. Jiang, Z. Y. Lu, L. Li, J. L. Wang, J. Li, and J. C. Li, Antimicrob Agents Chemother 59:2189–2197, 2015, http://dx.doi.org/10.1128/AAC.04092-14 ; H. Jiang, J. C. Li, T. Zhou, C. H. Wang, H. Zhang, and H. Wang, Int J Mol Med 33:1298–1304, 2014, http://dx.doi.org/10.3892/ijmm.2014.1684 ) indicates that colistin induces autophagy and apoptosis in rat adrenal medulla PC-12 cells, and there is interplay between both cellular events. As an important cellular stress sensor, phosphoprotein p53 can trigger cell cycle arrest and apoptosis and regulate autophagy. The aim of the present study was to investigate the involvement of the p53 pathway in colistin-induced neurotoxicity in PC-12 cells. Specifically, cells were treated with colistin (125 μg/ml) in the absence and presence of a p53 inhibitor, pifithrin-α (PFT-α; 20 nM), for 12 h and 24 h, and the typical hallmarks of autophagy and apoptosis were examined by fluorescence/immunofluorescence microscopy and electron microscopy, real-time PCR, and Western blotting. The results indicate that colistin had a stimulatory effect on the expression levels of the target genes and proteins involved in autophagy and apoptosis, including LC3-II/I, p53, DRAM (damage-regulated autophagy modulator), PUMA (p53 upregulated modulator of apoptosis), Bax, p-AMPK (activated form of AMP-activated protein kinase), and caspase-3. In contrast, colistin appeared to have an inhibitory effect on the expression of p-mTOR (activated form of mammalian target of rapamycin), which is another target protein in autophagy. Importantly, analysis of the levels of p53 in the cells treated with colistin revealed an increase in nuclear p53 at 12 h and cytoplasmic p53 at 24 h. Pretreatment of colistin-treated cells with PFT-α inhibited autophagy and promoted colistin-induced apoptosis. This is the first study to demonstrate that colistin-induced autophagy and apoptosis are associated with the p53-mediated pathway.

Emodin is an anthraquinone isolated from the Chinese herb Radix et Rhizoma Rhei and has been used to treat various diseases for centuries. The aim of the present study was to investigate the effect of emodin on the inflammatory mediators in rat chondrocytes. In the present study, chondrocytes were isolated from rats, cultured and harvested when they reached generation P3. Cells were treated with different doses of emodin (10, 20, and 30 µg/ml) followed by interleukin 1β (IL‑1β, 10 ng/ml). Control cells were either untreated or treated with IL‑1β alone. An enzyme‑linked immunosorbent assay was used to measure levels of nitric oxide (NO) and prostaglandin E2 (PGE2). Reverse transcription‑quantitative polymerase chain was performed to measure levels of matrix metallopeptidase (MMP)‑3 and ‑13 mRNA. The expression of MMP‑3, MMP‑13, extracellular‑signal regulatory kinase (ERK)1/2, phosphorylated ERK1/2 and β‑catenin proteins were detected by western‑blot analysis. The results demonstrated that treatment with emodin treatment reduced the cytotoxicity of IL‑1β and inhibited the expression of NO and PGE2 in rat chondrocytes. Furthermore, emodin inhibited the expression of MMP3 and MMP13, and the phosphorylation of various proteins involved in the ERK and Wnt/β‑catenin pathway. Therefore, emodin is able to promote the proliferation of chondrocytes by inhibiting the ERK and Wnt/β‑catenin pathway and downregulating the expression of a series of inflammatory mediators in chondrocytes.