Late activation of stress-activated protein kinases/c-Jun N-terminal kinases triggered by cisplatin-induced DNA damage in repair-defective cells

Enhanced phosphorylation of c-Jun by cisplatin treatment as a potential predictive biomarker for cisplatin response in combination with patient-derived tumor organoids

Despite recent advances in sequencing technology and large-scale drug screenings employing hundreds of cell lines, the predictive accuracy of mutation-based biomarkers is still insufficient as a guide for cancer therapy. Therefore, novel types of diagnostic methods using alternative biomarkers would be highly desirable. We have hypothesized that sensitivity-specific changes in the phosphorylation of signaling molecules could be useful in this respect. Here, with the aim of developing a method for predicting the response of cancers to cisplatin using a combination of specific biomarker(s) and patient-derived tumor organoids (PDOs), we found that cisplatin-sensitive cell lines or PDOs showed enhanced phosphorylation of c-Jun (p-c-Jun) within 24 h after cisplatin treatment. We also compared the responses of 6 PDOs to cisplatin with the therapeutic effect of neoadjuvant chemotherapy (docetaxel/cisplatin/5-fluorouracil) in 6 matched patients. Mechanistically, the c-Jun induction was partly related to TNF signaling induced by cisplatin. Our data suggest that enhanced phosphorylation of c-Jun in response to cisplatin treatment could be a predictive biomarker for the efficacy of cisplatin in selected cancer patients.

Pleiotropic effects of statins: A focus on cancer

The statin drugs ('statins') potently inhibit hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase by competitively blocking the active site of the enzyme. Statins decrease de novo cholesterol biosynthesis and thereby reduce plasma cholesterol levels. Statins exhibit "pleiotropic" properties that are independent of their lipid-lowering effects. For example, preclinical evidence suggests that statins inhibit tumor growth and induce apoptosis in specific cancer cell types. Furthermore, statins show chemo-sensitizing effects by impairing Ras family GTPase signaling. However, whether statins have clinically meaningful anti-cancer effects remains an area of active investigation. Both preclinical and clinical studies on the potential mechanisms of action of statins in several cancers have been reviewed in the literature. Considering the contradictory data on their efficacy, we present an up-to-date summary of the pleiotropic effects of statins in cancer therapy and review their impact on different malignancies. We also discuss the synergistic anti-cancer effects of statins when combined with other more conventional anti-cancer drugs to highlight areas of potential therapeutic development.

Activity profile of the cisplatin analogue PN149 in different tumor cell lines

The efficacy of the anticancer drug cisplatin is restricted by tumor cell resistance and occurrence of severe side effects. One strategy to overcome these limitations is the development of new, improved platinum drugs. Previous investigations showed that platinum(IV)-nitroxyl complexes are able to circumvent cisplatin resistance in bladder cancer cells. In the present study the mode of action of the platinum(IV)-nitroxyl complex PN149 was investigated in the bladder cancer cell line RT112 and the renal cell carcinoma cell line A498 on the molecular and cellular level. Gene expression analysis showed that PN149 induced genes related to DNA damage response (RRM2B, GADD45A), cell cycle regulation (CDKN1A, PLK3, PPM1D) as well as those coding for the pro-apoptotic factors PUMA and Noxa. These findings on the transcriptional level were confirmed on the functional level revealing that PN149 treatment increased levels of p53 and resulted in cell cycle arrest and drug-induced cytotoxicity via induction of apoptosis. Regarding the expression of oxidative-stress sensitive genes, PN149 induced FTH1, GCLC, HMOX1 and TXNRD1 but relevant effects were restricted to RT112 cells treated with 50 µM. The pro-inflammatory IL-8 was induced by PN149 in RT112 but not A498 cells indicating a cell-type specific activation. Taken together, PN149 possessed promising activity in different tumor cell lines rendering it an interesting alternative to cisplatin in chemotherapy.

GLIPR1 modulates the response of cisplatin-resistant human lung cancer cells to cisplatin

Background and objective

Chemotherapy drugs, such as cisplatin (DDP), improve the survival of patients with lung cancer by inducing apoptosis in cancer cells, which quickly develop resistance to DDP through uncharacterized mechanisms. Glioma Pathogenesis-Related Protein 1 (GLIPR1) plays an important role in cell proliferation, migration and apoptosis. However, the expression and function of GLIPR1 in mediating DDP resistance in human lung adenocarcinoma A549/DDP and human large cell lung cancer H460/DDP cells has not yet been reported.

Methods

In this study, real-time PCR (RT-PCR) and western blot were used to examine the mRNA and protein expression of GLIPR1, respectively. Bright-field microscopy, the cell counting kit-8 (CCK-8) assay, flow cytometry analysis and JC-1 dye were used to measure the cellular morphology, proliferation, apoptosis and mitochondrial membrane potential, respectively.

Results

Compared to human lung adenocarcinoma A549 cells, the mRNA and protein expression of GLIPR1 were significantly increased in DDP-resistant A549/DDP cells (p < 0.05). Similarly, the mRNA level of GLIPR1 in DDP-resistant H460/DDP cells was also significantly higher than that in DDP-sensitive H460 cells (p < 0.05). Silencing of GLIPR1 in A549/DDP and H460/DDP cells led to increased apoptosis via a mitochondrial signaling pathway following incubation with various concentrations of DDP. Furthermore, GLIPR1 downregulation markedly reduced the protein expression of Bcl-2, and increased the cleaved Poly (ADP-Ribose) Polymerase (PARP) and cleaved caspase-3 in DDP-resistant A549/DDP cells.

Conclusion

In this study, we demonstrated for the first time that GLIPR1 could modulate the response of DDP-resistant A549/DDP and H460/DDP cells to cisplatin. Therefore, GLIPR1 deserves further investigation in the context of none-small lung cancer (NSCLC).

Knockdown of ST6Gal-I increases cisplatin sensitivity in cervical cancer cells

Background

Sialyltransferase I (ST6Gal-I) is an enzyme involved in tumor metastasis that processes sialic acid precursors into their mature form, enabling them to regulate gene expression. However, the effect of ST6Gal-I on the biological behavior of cancer cells remain unclear. This study was the first to demonstrate the influence of ST6Gal-I on cisplatin sensitivity in cervical cancer cells.

Methods

Knockdown of ST6Gal-I was performed by shRNA and HeLa cells combination with cisplatin were tested.

Results

We showed that down-regulation of ST6Gal-I promoted cell apoptosis and inhibited proliferation and invasion in cervical cancer cells. Knockdown of ST6Gal-I by RNA interference increased the sensitivity of HeLa cells to cisplatin in vitro, and reduced tumor volume and suppressed subcutaneous tumor growth in response to cisplatin treatment in a xenograft mouse model in vivo.

Conclusions

The results provide new information that ST6Gal-I plays an important role in several biological or pathological processes including drug resistance in cervical cancer and may be a potential therapeutic target to improve the response to chemotherapy in cervical cancer patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2981-y) contains supplementary material, which is available to authorized users.

Rho GTPases: Novel Players in the Regulation of the DNA Damage Response?

The Ras-related C3 botulinum toxin substrate 1 (Rac1) belongs to the family of Ras-homologous small GTPases. It is well characterized as a membrane-bound signal transducing molecule that is involved in the regulation of cell motility and adhesion as well as cell cycle progression, mitosis, cell death and gene expression. Rac1 also adjusts cellular responses to genotoxic stress by regulating the activity of stress kinases, including c-Jun-N-terminal kinase/stress-activated protein kinase (JNK/SAPK) and p38 kinases as well as related transcription factors. Apart from being found on the inner side of the outer cell membrane and in the cytosol, Rac1 has also been detected inside the nucleus. Different lines of evidence indicate that genotoxin-induced DNA damage is able to activate nuclear Rac1. The exact mechanisms involved and the biological consequences, however, are unclear. The data available so far indicate that Rac1 might integrate DNA damage independent and DNA damage dependent cellular stress responses following genotoxin treatment, thereby coordinating mechanisms of the DNA damage response (DDR) that are related to DNA repair, survival and cell death.

XPC: Going where no DNA damage sensor has gone before

XPC has long been considered instrumental in DNA damage recognition during global genome nucleotide excision repair (GG-NER). While this recognition is crucial for organismal health and survival, as XPC's recognition of lesions stimulates global genomic repair, more recent lines of research have uncovered many new non-canonical pathways in which XPC plays a role, such as base excision repair (BER), chromatin remodeling, cell signaling, proteolytic degradation, and cellular viability. Since the first discovery of its yeast homolog, Rad4, the involvement of XPC in cellular regulation has expanded considerably. Indeed, our understanding appears to barely scratch the surface of the incredible potential influence of XPC on maintaining proper cellular function. Here, we first review the canonical role of XPC in lesion recognition and then explore the new world of XPC function.

Oxysterol-binding protein (OSBP)-related protein 4 (ORP4) is essential for cell proliferation and survival

Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) comprise a large gene family with sterol/lipid transport and regulatory activities. ORP4 (OSBP2) is a closely related paralogue of OSBP, but its function is unknown. Here we show that ORP4 binds similar sterol and lipid ligands as OSBP and other ORPs but is uniquely required for the proliferation and survival of cultured cells. Recombinant ORP4L and a variant without a pleckstrin homology (PH) domain (ORP4S) bind 25-hydroxycholesterol and extract and transfer cholesterol between liposomes. Two conserved histidine residues in the OSBP homology domain ORP4 are essential for binding phosphatidylinositol 4-phosphate but not sterols. The PH domain of ORP4L also binds phosphatidylinositol 4-phosphate in the Golgi apparatus. However, in the context of ORP4L, the PH domain is required for normal organization of the vimentin network. Unlike OSBP, RNAi silencing of all ORP4 variants (including a partial PH domain truncation termed ORP4M) in HEK293 and HeLa cells resulted in growth arrest but not cell death. ORP4 silencing in non-transformed intestinal epithelial cells (IEC)-18 caused apoptosis characterized by caspase 3 and poly(ADP-ribose) polymerase processing, DNA cleavage, and JNK phosphorylation. IEC-18 transformed with oncogenic H-Ras have increased expression of ORP4L and ORP4S proteins and are resistant to the growth-inhibitory effects of ORP4 silencing. Results suggest that ORP4 promotes the survival of rapidly proliferating cells.

Overexpressed DNA polymerase iota regulated by JNK/c-Jun contributes to hypermutagenesis in bladder cancer

Human DNA polymerase iota (pol ι) possesses high error-prone DNA replication features and performs translesion DNA synthesis. It may be specialized and strictly regulated in normal mammalian cells. Dysregulation of pol ι may contribute to the acquisition of a mutator phenotype. However, there are few reports describing the transcription regulatory mechanism of pol ι, and there is controversy regarding its role in carcinogenesis. In this study, we performed the deletion and point-mutation experiment, EMSA, ChIP, RNA interference and western blot assay to prove that c-Jun activated by c-Jun N-terminal kinase (JNK) regulates the transcription of pol ι in normal and cancer cells. Xeroderma pigmentosum group C protein (XPC) and ataxia-telangiectasia mutated related protein (ATR) promote early JNK activation in response to DNA damage and consequently enhance the expression of pol ι, indicating that the novel role of JNK signal pathway is involved in DNA damage response. Furthermore, associated with elevated c-Jun activity, the overexpression of pol ι is positively correlated with the clinical tumor grade in 97 bladder cancer samples and may contribute to the hypermutagenesis. The overexpressed pol ι-involved mutagenesis is dependent on JNK/c-Jun pathway in bladder cancer cells identifying by the special mutation spectra. Our results support the conclusion that dysregulation of pol ι by JNK/c-Jun is involved in carcinogenesis and offer a novel understanding of the role of pol ι or c-Jun in mutagenesis.

Modulation of the response of prostate cancer cell lines to cisplatin treatment using small interfering RNA

Cisplatin is one of the most effective and widely used chemotherapeutic agents against several types of human cancers. However, the underlying mechanisms of action are not fully understood. We aimed to investigate the possible molecular mechanism(s) of acquired chemoresistance observed in prostate cancer cells treated with cisplatin. Human LNCaP cells (bearing wild-type p53) and PC-3 cells (lacking p53) were used. The expression levels of protein were determined by western blotting, and the mRNA levels were determined by reverse transcription-polymerase chain reaction (RT-PCR). Cell viability was measured by MTT assay, and the transcriptional effect of small interfering RNA (siRNA) was measured by luciferase reporter gene. We showed that cisplatin treatment increased JNK-1 and JNK-2 activity and expression in both LNCaP and PC-3 cells. In addition, the knockdown of JNK-1 expression by siRNA-JNK-1 or siRNA-JNK-2 significantly impaired the upregulation of AP-1 luciferase reporter gene, but failed to decrease the levels of AP-1 reporter gene expression induced by TPA treatment. Our observations indicate that JNK-1 and JNK-2 may be involved in the chemoresistance observed in prostate cancer cells treated with cisplatin and that blocking the stimulation of Jun kinase (JNK) signaling may be important for regulating the susceptibility to cisplatin of prostate cancer.

Role of p53 in Anticancer Drug Treatment- and Radiation-Induced Injury in Normal Small Intestine

In the human gastrointestinal tract, the functional mucosa of the small intestine has the highest capacity for absorption of nutrients and rapid proliferation rates, making it vulnerable to chemoradiotherapy. Recent understanding of the protective role of p53-mediated cell cycle arrest in the small intestinal mucosa has led researchers to explore new avenues to mitigate mucosal injury during cancer treatment. A traditional p53 inhibitor and two other molecules that exhibit strong protective effects on normal small intestinal epithelium during anticancer drug treatment and radiation therapy are introduced in this work. The objective of this review was to update current knowledge regarding potential mechanisms and targets that inhibit the side effects induced by chemoradiotherapy.

Dexamethasone reduces sensitivity to cisplatin by blunting p53-dependent cellular senescence in non-small cell lung cancer

Introduction

Dexamethasone (DEX) co-treatment has proved beneficial in NSCLC patients, improving clinical symptoms by the reduction of side effects after chemotherapy. However, recent studies have shown that DEX could render cancer cells more insensitive to cytotoxic drug therapy, but it is not known whether DEX co-treatment could influence therapy-induced senescence (TIS), and unknown whether it is in a p53-dependent or p53-independent manner.

Methods

We examined in different human NSCLC cell lines and detected cellular senescence after cisplatin (DDP) treatment in the presence or absence of DEX. The in vivo effect of the combination of DEX and DDP was assessed by tumor growth experiments using human lung cancer cell lines growing as xenograft tumors in nude mice.

Results

Co-treatment with DEX during chemotherapy in NSCLC resulted in increased tumor cell viability and inhibition of TIS compared with DDP treated group. DEX co-treatment cells exhibited the decrease of DNA damage signaling pathway proteins, the lower expression of p53 and p21^CIP1, the lower cellular secretory program and down-regulation of NF-κB and its signaling cascade. DEX also significantly reduced DDP sensitivity in vivo.

Conclusions

Our results underscore that DEX reduces chemotherapy sensitivity by blunting therapy induced cellular senescence after chemotherapy in NSCLC, which may, at least in part, in a p53-dependent manner. These data therefore raise concerns about the widespread combined use of gluocorticoids (GCs) with antineoplastic drugs in the clinical management of cancer patients.

Statins and cancer: current and future prospects

Statins are inhibitors of 3-hydroxy-methylglutaryl (HMG) CoA reductase. They exhibit effects beyond cholesterol reduction, including anticancer activity. This review presents the effects of statins in vitro and their possible molecular anticancer mechanisms and critically discusses the data regarding the role of statins in cancer prevention. Finally, this review focuses on the use of statins combined with other chemotherapeutics to increase the effectiveness of cancer treatments. Despite rare and inconclusive clinical data, the preclinical results strongly suggest that such combined treatment could be a promising new strategy for the treatment of certain tumor types.