Cisplatin-induced Cell Death Research Articles

MiR-222 attenuates cisplatin-induced cell death by targeting the PPP2R2A/Akt/mTOR Axis in bladder cancer cells.

Increased miR-222 levels are associated with a poor prognosis in patients with bladder cancer. However, the role of miR-222 remains unclear. In the present study, we found that miR-222 enhanced the proliferation of both the T24 and the 5637 bladder cancer cell lines. Overexpression of miR-222 attenuated cisplatin-induced cell death in bladder cancer cells. miR-222 activated the Akt/mTOR pathway and inhibited cisplatin-induced autophagy in bladder cancer cells by directly targeting protein phosphatase 2A subunit B (PPP2R2A). Blocking the activation of Akt with LY294002 or mTOR with rapamycin significantly prevented miR-222-induced proliferation and restored the sensitivity of bladder cancer cells to cisplatin. These findings demonstrate that miR-222 modulates the PPP2R2A/Akt/mTOR axis and thus plays a critical role in regulating proliferation and chemotherapeutic drug resistance. Therefore, miR-222 may be a novel therapeutic target for bladder cancer.

Targeting acid ceramidase sensitises head and neck cancer to cisplatin

BackgroundAcid ceramidase (AC), a key enzyme in ceramide metabolism, plays a role in cancer progression and resistance to therapy. However, the role of AC in head and neck cancer (HNC) has not been addressed. Here, we investigate the effect of AC inhibition on the response to cisplatin-based chemotherapy for HNC. MethodsAC protein and messenger RNA (mRNA) expression were examined in primary tumours and paired normal tissues, and in HNC cell lines. The effects of genetic and pharmacological AC inhibition using small hairpin RNA (shRNA) and N-oleoyl-ethanolamine (NOE), alone and in combination with cisplatin, were assessed in human HNC cells by measuring cell viability, cell cycle progression, apoptosis, mRNA, and protein expression, and in preclinical tumour xenograft mouse models. FindingsAC overexpression was observed in four of six primary tumour tissues and six of nine HNC cell lines. Cisplatin sensitivity was significantly decreased by AC overexpression and significantly increased by AC downregulation in HNC cells (P<0.01). NOE or AC shRNA-mediated AC inhibition enhanced cisplatin-induced HNC cell death by increasing ceramide production and activating pro-apoptotic proteins, and these effects were abrogated by PUMA small interfering RNA transfection. AC inhibition promoted cisplatin-induced apoptosis of HNC cells in vitro and in vivo. InterpretationsAC overexpression is associated with cisplatin sensitivity, suggesting its potential role as a chemotherapeutic target for HNC. Genetic or pharmacological AC inhibition promotes cisplatin cytotoxicity in HNC cells.

Role of BCL2-associated athanogene in resistance to platinum-based chemotherapy in non-small-cell lung cancer.

The present study aimed to address the pharmacogenetic role of BAG1 in platinum-based chemotherapy in advanced non-small-cell lung cancer (NSCLC) and in cultured human lung adenocarcinoma A549 cells. A total of 108 NSCLC patients (stages I–IIIA) were treated with a standard chemotherapy regimen of cisplatin plus vinorelbine. Additionally, in vitro cultured A549 cells were treated with cisplatin in the presence or absence of tunicamycin. Cell proliferation was determined by MTT assay and protein levels were assessed via western blot analysis. Patients with BAG1-positive expression were revealed to have a prolonged survival time (progression-free survival, 24.0 months) compared with that of patients without BAG1 expression (21.6 months; χ2=18.018, P<0.05). Treatment of A549 cells with tunicamycin followed by cisplatin resulted in elevated BAG1 levels. In addition, tunicamycin was found to significantly enhance cisplatin-induced growth inhibition and apoptosis in A549 cells. The results indicate that BAG1 is important in cisplatin-induced cell death in lung adenocarcinoma, suggesting that endoplasmic reticulum stress may promote the sensitivity of NSCLC patients to chemotherapy.

Intracellular prostaglandin E2 mediates cisplatin-induced proximal tubular cell death

Nephrotoxicity, particularly in the proximal tubule, limits the therapeutic efficacy of the antineoplastic drug cisplatin. The signaling mechanisms appear to be multifactorial, involving inflammation, oxidative stress, and caspase. Here we studied the role of intracellular prostaglandin E2 (iPGE2) in cisplatin's cytotoxicity in human proximal tubular HK-2 cells. Cisplatin-induced apoptotic cell death was prevented by inhibitors of the prostaglandin transporter (PGT) or by PGT knock-down or by pharmacologic inhibition of PGE2 EP receptors or cyclo-oxygenase-2 (COX-2). iPGE2 also increased in cisplatin-treated cells, which was probably due to increased expression of COX-2, microsomal PGE2 synthase-1 and PGT, and was prevented by inhibitors of PGT or COX-2. Thus iPGE2, most likely acting through intracellular EP receptors, mediates cisplatin-induced HK-2 cell death. Importantly, the tumoricidal effect of cisplatin on human cervical adenocarcinoma HeLa cells was not affected by a pharmacologic inhibitor of PGT. In conclusion, iPGE2 may play a significant role in the pathogenesis of cisplatin’s nephrotoxicity and treatment with PGT inhibitors might represent a novel strategy in its prevention.

VEGF-activated miR-144 regulates autophagic survival of prostate cancer cells against Cisplatin.

Cisplatin is a commonly used chemotherapy drug for prostate cancer (PC). However, some PCs are resistant to cisplatin treatment, while the molecular mechanisms underlying the resistance of PCs to cisplatin are not completely understood. In this study, we found that cisplatin dose-dependently activated Beclin-1 in two PC cell lines, PC3 and LNCap. Autophagy suppression significantly increased the cisplatin-induced cell death of these PC cells in a CCK-8 assay. Moreover, microRNA (miR)-144 levels were significantly downregulated in cisplatin-treated PC cells, in a VEGF-dependent manner. Bioinformatics analysis showed that miR-144 targeted the 3'-UTR of Beclin-1 mRNA to inhibit its translation, which was confirmed by luciferase reporter assay. In PC patients after cisplatin treatment, low miR-144 levels appeared to predict poor outcome of patients' survival. Together, these data suggest that cisplatin may induce VEGF to suppress miR-144 levels in PC cells, which subsequently upregulates Beclin-1 to increase autophagic cell survival against cisplatin-induced cell death. Upregulation of miR-144 or suppression of cell autophagy may improve the outcome of cisplatin therapy in PC.

STAT1 Activation Is Enhanced by Cisplatin and Variably Affected by EGFR Inhibition in HNSCC Cells.

Cisplatin is a cytotoxic chemotherapeutic drug frequently used to treat many solid tumors, including head and neck squamous cell carcinoma (HNSCC). EGF receptor (EGFR) inhibitors have also shown efficacy as alternatives to cisplatin in some situations. However, large clinical trials have shown no added survival benefit from the use of these two drugs in combination. Possible explanations for this include overlapping downstream signaling cascades. Using in vitro studies, we tested the hypothesis that cisplatin and EGFR inhibitors rely on the activation of the tumor suppressor STAT1, characterized by its phosphorylation at serine (S727) or tyrosine (Y701) residues. Cisplatin consistently increased the levels of p-S727-STAT1, and STAT1 siRNA knockdown attenuated cisplatin-induced cell death. EGFR stimulation also activated p-S727-STAT1 and p-Y701-STAT1 in a subset of cell lines, whereas EGFR inhibitors alone decreased levels of p-S727-STAT1 and p-Y701-STAT1 in these cells. Contrary to our hypothesis, EGFR inhibitors added to cisplatin treatment caused variable effects among cell lines, with attenuation of p-S727-STAT1 and enhancement of cisplatin-induced cell death in some cells and minimal effect in other cells. Using HNSCC tumor specimens from a clinical trial of adjuvant cisplatin plus the anti-EGFR antibody panitumumab, higher intratumoral p-S727-STAT1 appeared to correlate with worse survival. Together, these results suggest that cisplatin-induced cell death is associated with STAT1 phosphorylation, and the addition of anti-EGFR therapy to cisplatin has variable effects on STAT1 and cell death in HNSCC.

Mechanism of Cisplatin-Induced Cytotoxicity Is Correlated to Impaired Metabolism Due to Mitochondrial ROS Generation.

The chemotherapeutic use of cisplatin is limited by its severe side effects. In this study, by conducting different omics data analyses, we demonstrated that cisplatin induces cell death in a proximal tubular cell line by suppressing glycolysis- and tricarboxylic acid (TCA)/mitochondria-related genes. Furthermore, analysis of the urine from cisplatin-treated rats revealed the lower expression levels of enzymes involved in glycolysis, TCA cycle, and genes related to mitochondrial stability and confirmed the cisplatin-related metabolic abnormalities. Additionally, an increase in the level of p53, which directly inhibits glycolysis, has been observed. Inhibition of p53 restored glycolysis and significantly reduced the rate of cell death at 24 h and 48 h due to p53 inhibition. The foremost reason of cisplatin-related cytotoxicity has been correlated to the generation of mitochondrial reactive oxygen species (ROS) that influence multiple pathways. Abnormalities in these pathways resulted in the collapse of mitochondrial energy production, which in turn sensitized the cells to death. The quenching of ROS led to the amelioration of the affected pathways. Considering these observations, it can be concluded that there is a significant correlation between cisplatin and metabolic dysfunctions involving mROS as the major player.

Abstract 138: Novel PAK4 allosteric modulators (PAMs) provide potential therapeutic options in human gastric cancer

Abstract Expression of PAK4 (p21-activated serine/threonine kinase 4) is associated with gastric tumorigenesis. Overexpression of PAK4 is correlated with metastasis of gastric cancer and in part confers cisplatin resistance in gastric cancer patients. We transduced the human gastric cancer cell line AGS with CRISPR/cas9 targeting PAK4, and observed reduced cell proliferation and motility. Novel PAK4 allosteric modulators (PAMs) were evaluated for their potential therapeutic use for gastric cancer. A panel of human gastric cancer cell lines was screened with four PAMs (KPT-7189, -7349, -7657, -8752). MTS assay showed inhibition of cell viability by PAMs in 6 of 10 gastric cancer cell lines (IC50 ranged from 50 to 5000 nM). Cell cycle analysis and annexin V assay indicated a combination of cell growth arrest at G1 phase and cell apoptosis after treatment with PAMs. Furthermore, PAMs diminished expression levels of PAK4, induced apoptosis-related molecule caspase-3, and suppressed PI3K/Akt and MEK/Erk signaling. Wound assay showed inhibition of cell migration and soft agar assay demonstrated suppression of colony formation for gastric cancer cells treated with PAMs. Mouse xenograft models are currently under investigation. Remarkably, PAMs in combination with cisplatin induced cell death in cisplatin-resistant gastric cancer cells in a synergistic manner. This study demonstrates PAMs have anti-tumor activity against gastric cancer cells and suggests their potential use for the treatment of gastric cancer. Citation Format: Wenwen Chien, Jinfen Xiao, Ling-Wen Ding, Muhammad Ikhsan B. Muzakar, Qiao-Yang Sun, Sigal Gery, William Senapedis, Sharon Shacham, Erkan Baloglu, H. Phillip Koeffler. Novel PAK4 allosteric modulators (PAMs) provide potential therapeutic options in human gastric 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 138. doi:10.1158/1538-7445.AM2015-138

Abstract 5475: Cancer exosome promotes cisplatin resistance In bladder cancer and inhibition of exosome sensitizes bladder cancer cells to cisplatin chemotherapy

Abstract Exsosomes are nano-vesicles secreted by most types of cells, and substantially increased secretion in cancer cells. Their role in tumorigenesis/cancer progression have been extensively studied but their role in regulating therapy response have been suggested without in depth investigation. We are particularly interested in exosome's roles in cisplatin resistant, since cisplatin is one of the most widely used chemodrugs for many cancer types. To investigate the role of exosomes in cisplatin resistance in bladder cancer, we examined the cisplatin sensitivity among five bladder cancer cell lines. The expression levels of exosome associated genes that are involved in exosome biogenesis and secretion/internalization were examined by quantative PCR. Interestingly, cisplatin resistant bladder cancer cells express relative high level of exosome associated genes as compared to cisplatin sensitive cells. More importantly, cisplatin treatment induces the expression of exosome associated genes’ expression in cisplatin resistant cells, but not in sensitive cell. Among all those genes, we are particularly interested in Rab gene family, and mechanistic study of targeting those Rab proteins is undergoing. The correlative exosome genes profiles with cisplatin resistance suggested exosome production might facilitate cancer cells escaping from cisplatin-induced cell death; thereby, inhibition of exosome might sensitize cancer cells response to cisplatin. To test this, we have screened several compounds that are known to inhibit exosome biogenesis and uptake, and. found that inhibition of exosomes by dynasore + NSC23766, indeed can sensitize bladder cancer cells to cisplatin. In summary, we concluded that cancer exosome play a critical role of promoting cisplatin resistance in bladder cancer, and inhibition of exosomes sensitizes bladder cancer cell response to cisplain. The exosome related profiles potentially can serve as therapy biomarkers Citation Format: Chiahao Wu, Chris Silvers, Elizabeths Guancial, Jong-Wei Hsu, Edward Messing, Yi-Fen Lee. Cancer exosome promotes cisplatin resistance In bladder cancer and inhibition of exosome sensitizes bladder cancer cells to cisplatin chemotherapy. [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 5475. doi:10.1158/1538-7445.AM2015-5475

Inhibition of Glucosylceramide Synthase Sensitizes Head and Neck Cancer to Cisplatin.

Glucosylceramide synthase (GCS) overexpression is associated with multidrug resistance in several human cancers. GCS blockade, which overcomes multidrug resistance by downregulating P-glycoprotein (P-gp), has not been tested in head and neck cancer (HNC). This study investigates whether GCS is targetable in HNC by assessing whether GCS inhibition sensitizes HNC to cisplatin. The effect of genetic or pharmacologic GCS inhibition (using GCS siRNA/shRNA or d,l-threo-PPMP, respectively) on cisplatin sensitivity was assessed in several human HNC cells and acquired cisplatin-resistant HNC cells by measuring cell viability, cell cycle, death, mRNA and protein expression, ceramide production, and in preclinical tumor xenograft mouse models. GCS and P-gp expression were significantly associated with cisplatin resistance in several HNC cell lines (P = 0.007). Both were significantly increased in HN9-cisR cells, which display acquired cisplatin resistance (P < 0.001). Genetic or pharmacologic inhibition of GCS induced accumulation of increased ceramide levels. GCS inhibition increased cisplatin-induced cell death in HNC cells via P-gp downregulation and proapoptotic protein activation, which were abrogated by siPUMA transfection. Genetic and pharmacologic GCS inhibition sensitized resistant HNC cells to cisplatin in vitro and in vivo. GCS and P-gp overexpression is associated with acquired cisplatin resistance, suggesting a role for these molecules as therapeutic targets for HNC. Genetic or pharmacologic GCS blockade may have therapeutic benefit in cisplatin-resistant HNC.

Abstract 4431: Musashi enhances GS3K-beta and promotes stemness-related chemoresistance in glioblastoma

Abstract Glioblastoma multiforme (GBM), one of the deadly malignant brain tumor, and is easily to recur and develop resistance to clinical chemotherapeutics. It has been demonstrated that cisplatin treatment select for resistance but also for a more oncogenic phenotype characterized by high self-renewal and oncogenic resistance. Musashi (MSI), a neural stem cell marker, is found to be elevated in several cancer tissues and positively regulates cancer progression. In this report, we found that MSI promoted tumourigenicity and enhances drug resistance of human GBM cells in response to cisplatin, a chemodrug. We further showed that MSI could activate and interact with phosphorylated-GS3K-β, and lead to a protective effect against mitigating cisplatin-induced cell death. Knockdown of MSI effectively suppressed the phosphorylation of GS3K-β and blocked β-catenin translocating into nucleus in cisplatin-resistant GBM cells, while overexpressing MSI reversed these effects. Notably, MSI could further upregulate β-catenin-driven stemness signature, and expression of Oct-4, Nanog, and ABCG2, thereby enhanced tumorigenicity and chemoresistance of GBM cells. Moreover, the result of in vivo animal study demonstrated that knockdown MSI effectively suppressed stem-like properties, synergistically enhanced the chemotherapeutic effect, and significantly improved survival rate in GBM-transplanted immunocompromised mice. Taken together, our findings indicated that MSI-1 may provide a positive contribution to oncogenic resistance, in partly, through interplaying with GS3K-β and modulating WNT/stemness mechanism. Note: This abstract was not presented at the meeting. Citation Format: Hsiao-Yun Chen, Shih-Hwa Chiou. Musashi enhances GS3K-beta and promotes stemness-related chemoresistance in glioblastoma. [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 4431. doi:10.1158/1538-7445.AM2015-4431

Honey feeding protects kidney against cisplatin nephrotoxicity through suppression of inflammation.

Cisplatin is a highly effective chemotherapeutic drug used to treat a wide variety of solid tumors. However, its use was limited due its dose-limiting toxicity to the kidney. Currently, there are no therapies available to treat or prevent cisplatin nephrotoxicity. Honey is a naturally occurring complex liquid and widely used in traditional Ayurvedic medicine to treat many illnesses. However, its effect on cisplatin nephrotoxicity is unknown. To determine the role of honey in cisplatin nephrotoxicity, animals were pretreated orally for a week and then cisplatin was administered. Honey feeding was continued for another 3 days. Our results show that animals with cisplatin-induced kidney dysfunction, as determined by increased serum creatinine, which received honey feeding had less kidney dysfunction. Improved kidney function was associated with better preservation of kidney morphology in honey-treated group as compared to the cisplatin alone-treated group. Interestingly, honey feeding significantly reduced cisplatin-induced tubular epithelial cell death, immune infiltration into the kidney as well as cytokine and chemokine expression and excretion as compared to cisplatin treated animals. Western blot analysis shows that cisplatin-induced increase in phosphorylation of NFkB was completely suppressed with honey feeding. In conclusion, honey feeding protects the kidney against cisplatin nephrotoxicity through suppression of inflammation and NFkB activation.

Hypoxia-induced autophagy mediates cisplatin resistance in lung cancer cells.

Hypoxia which commonly exists in solid tumors, leads to cancer cells chemoresistance via provoking adaptive responses including autophagy. Therefore, we sought to evaluate the role of autophagy and hypoxia as well as the underlying mechanism in the cisplatin resistance of lung cancer cells. Our study demonstrated that hypoxia significantly protected A549 and SPC-A1 cells from cisplatin-induced cell death in a Hif-1α- and Hif-2α- dependent manner. Moreover, compared with normoxia, cisplatin-induced apoptosis under hypoxia was markedly reduced. However, when autophagy was inhibited by 3-MA or siRNA targeted ATG5, this reduction was effectively attenuated, which means autophagy mediates cisplatin resisitance under hypoxia. In parallel, we showed that hypoxia robustly augmented cisplatin-induced autophagy activation, accompanying by suppressing cisplatin-induced BNIP3 death pathways, which was due to the more efficient autophagic process under hypoxia. Consequently, we proposed that autophagy was a protective mechanism after cisplatin incubation under both normoxia and hypoxia. However, under normoxia, autophagy activation ‘was unable to counteract the stress induced by cisplatin, therefore resulting in cell death, whereas under hypoxia, autophagy induction was augmented that solved the cisplatin-induced stress, allowing the cells to survival. In conclusion, augmented induction of autophagy by hypoxia decreased lung cancer cells susceptibility to cisplatin-induced apoptosis.

Antrodia cinnamomea alleviates cisplatin-induced hepatotoxicity and enhances chemo-sensitivity of line-1 lung carcinoma xenografted in BALB/cByJ mice.

Whereas cisplatin (cis-diamminedichloroplatinum II) is a first-line medicine to treat solid cancerous tumors, it often causes serious side effects. New medicines that have an equivalent or even better therapeutic effect but with free or less side effects than cisplatin are highly anticipated in cancer therapy. Recent reports revealed that Antrodia cinnamomea (AC) possesses hepatoprotective activity in addition to anticancer. In this study, we wanted to know whether AC enhances chemo-sensitivity of cisplatin and/or alleviates cisplatin-induced hepatotoxicity, as well as the underlying mechanisms thereof. Our results indicated that AC inhibited proliferation of line-1 lung carcinoma cells and rescued hepatic HepG2 cells from cisplatin-induced cell death in vitro. The fact is that AC and cisplatin synergized to constrain growth of line-1 lung carcinoma cells in BALB/cByJ mice. Quantitative real-time PCR further revealed that AC promoted expression of apoptosis-related genes, while it decreased expression of NF-κB and VEGF in tumor tissues. In liver, AC reduced cisplatin-induced liver dysfunctions, liver inflammation and hepatic apoptosis in addition to body weight restoration. In summary, AC is able to increase cisplatin efficacy by triggering expression of apoptosis-related genes in line-1 lung cancer cells as well as to protect liver from tissue damage by avoiding cisplatin-induced hepatic inflammation and cell death.

Defective TRAF3 modulates alternative NF-kB signaling and cytokine expression to promote cancer cell survival in HPV positive head and neck cancer (TUM10P.1049)

Abstract Persistent infection of high-risk human papillomaviruses (HPV) is a known pathogen associated with head and neck squamous cell carcinoma (HNSCC), especially in tonsil, oropharynx and oral cavity. The incidence of HPV+ HNSCC has been increased recently in the Unites States, while the molecular mechanism of virus promoting HNSCC has not been fully understood. Recently, The Cancer Genome Atlas (TCGA) project revealed unique homozygous and heterozygous deletions and mutations of TNF receptor-associated factor 3 (TRAF3) in HPV associated HNSCC tumors. Low expression of TRAF3 was observed in HPV positive HNSCC samples and cell lines with TRAF3 deletions. These tumors had elevated expression of NF-kB subunits involved in alternative pathway, such as NF-kB2 and RelB, often associated with increased NIK, cIAP1 and cIAP2 expression. Overexpression of TRAF3 in HPV+ cell lines significantly suppressed alternative NF-kB subunit NF-kB2/RELB nuclear localization, while increasing expression of IFNα/β and IL10 implicated in anti-viral immunity. Further, overexpression of TRAF3 inhibited cell growth, colony formation, and migration, and sensitized cells to TNF-a and cisplatin induced cell death. Our data revealed that defective TRAF3 activated alternative NF-kB signaling and suppressed anti-viral cytokine expression, which promoted cancer cell survival and drug resistance, especially in HPV+ HNSCC.

Identification of Small Molecule Inhibitors of Cisplatin-Induced Hair Cell Death

The zebrafish lateral line can be used to identify small molecules that protect against cisplatin-induced hair cell death. Cisplatin is a commonly used chemotherapeutic agent, which causes hearing loss by damaging hair cells of the inner ear. There are currently no FDA-approved pharmacologic strategies for preventing this side effect. The zebrafish lateral line has been used successfully in the past to study hair cell death and protection. In this study, we used the zebrafish lateral line to screen a library of 10,000 small molecules for protection against cisplatin-induced hair cell death. Dose-response relationships for identified protectants were determined by quantifying hair cell protection. The effect of each protectant on uptake of a fluorescent cisplatin analog was also quantified. From this screen, we identified 2 compounds exhibiting dose-dependent protection: cisplatin hair cell protectant 1 and 2 (CHCP1 and 2). CHCP1 reduced the uptake of a fluorescent cisplatin analog, suggesting its protective effects may be due to decreased cisplatin uptake. CHCP2 did not affect uptake, which suggests an intracellular mechanism of action. Evaluation of analogs of CHCP2 revealed 3 additional compounds that significantly reduced cisplatin-induced hair cell death, although none exceed the effectiveness or potency of the parent compound. The zebrafish lateral line was used to identify 2 small molecules that protected against cisplatin-induced hair cell death.

Vaccine-induced tumor necrosis factor-producing T cells synergize with cisplatin to promote tumor cell death.

Cancer immunotherapy, such as vaccination, is an increasingly successful treatment modality, but its interaction with chemotherapy remains largely undefined. Therefore, we explored the mechanism of synergy between vaccination with synthetic long peptides (SLP) of human papillomavirus type 16 (HPV16) and cisplatin in a preclinical tumor model for HPV16. SLP vaccination in this preclinical tumor model allowed the elucidation of novel mechanisms of synergy between chemo- and immunotherapy. By analyzing the tumor immune infiltrate, we focused on the local intratumoral effects of chemotherapy, vaccination, or the combination. Of several chemotherapeutic agents, cisplatin synergized best with SLP vaccination in tumor eradication, without requirement for the maximum-tolerated dose (MTD). Upon SLP vaccination, tumors were highly infiltrated with HPV-specific, tumor necrosis factor-α (TNFα)- and interferon-γ (IFNγ)-producing T cells. Upon combined treatment, tumor cell proliferation was significantly decreased compared with single treated and untreated tumors. Furthermore, we showed that TNFα strongly enhanced cisplatin-induced apoptotic tumor cell death in a JNK-dependent manner. This is consistent with upregulation of proapoptotic molecules and with enhanced cell death in vivo upon combined SLP vaccination and cisplatin treatment. In vivo neutralization of TNFα significantly reduced the antitumor responses induced by the combined treatment. Taken together, our data show that peptide vaccination with cisplatin treatment leads to decreased tumor cell proliferation and TNFα-induced enhanced cisplatin-mediated killing of tumor cells, together resulting in superior tumor eradication.

Novel High-Throughput Deoxyribonuclease 1 Assay

Deoxyribonuclease I (DNase I), the most active and abundant apoptotic endonuclease in mammals, is known to mediate toxic, hypoxic, and radiation injuries to the cell. Neither inhibitors of DNase I nor high-throughput methods for screening of high-volume chemical libraries in search of DNase I inhibitors are, however, available. To overcome this problem, we developed a high-throughput DNase I assay. The assay is optimized for a 96-well plate format and based on the increase of fluorescence intensity when fluorophore-labeled oligonucleotide is degraded by the DNase. The assay is highly sensitive to DNase I compared to other endonucleases, reliable (Z’ ≥ 0.5), and operationally simple, and it has low operator, intraassay, and interassay variability. The assay was used to screen a chemical library, and several potential DNase I inhibitors were identified. After comparison, 2 hit compounds were selected and shown to protect against cisplatin-induced kidney cell death in vitro. This assay will be suitable for identifying inhibitors of DNase I and, potentially, other endonucleases.

Protective role of quercetin against cisplatin-induced hair cell damage in zebrafish embryos.

The aim of this study was to evaluate the protective effects of quercetin on cisplatin-induced hair cell damage in transgenic zebrafish embryos. Five days postfertilization zebrafish embryos were exposed to 1 mM cisplatin and quercetin at 10, 50, 100, or 200 μM for 4 h. Hair cells within neuromasts of the supraorbital, otic, and occipital lateral lines were analyzed by fluorescent microscopy (n = 10). Survival of hair cells was calculated as the average number of hair cells in the control group that were not exposed to cisplatin. Ultrastructural changes were evaluated using scanning electron microscopy. Hair cell damage in neuromasts was decreased by co-treatment of quercetin and cisplatin (quercetin 100 μM: 8.6 ± 1.1 cells; 1 mM cisplatin only: 5.0 ± 0.5 cells; n = 10, p < 0.05); apoptosis of hair cells examined by special stain was also decreased by quercetin. The ultrastructure of hair cells within neuromasts was preserved in zebrafish by the combination of quercetin (100 μM) and cisplatin (1 mM). In conclusion, quercetin showed protective effects against cisplatin-induced toxicity in a zebrafish model. The results of this study suggest the possibility of a protective role of quercetin against cisplatin-induced apoptotic cell death in zebrafish.

Constitutively active ErbB2 regulates cisplatin-induced cell death in breast cancer cells via pro- and antiapoptotic mechanisms.

Despite the frequent expression of N-terminally truncated ErbB2 (ΔNErbB2/p95HER2) in breast cancer and its association with Herceptin resistance and poor prognosis, it remains poorly understood how ΔNErbB2 affects chemotherapy-induced cell death. Previously it was shown that ΔNErbB2 upregulates acid extrusion from MCF-7 breast cancer cells and that inhibition of the Na(+)/H(+) exchanger (SLC9A1/NHE1) strongly sensitizes ΔNErbB2-expressing MCF-7 cells to cisplatin chemotherapy. The aim of this study was to identify the mechanism through which ΔNErbB2 regulates cisplatin-induced breast cancer cell death, and determine how NHE1 regulates this process. Cisplatin treatment elicited apoptosis, ATM phosphorylation, upregulation of p53, Noxa (PMAIP1), and PUMA (BBC3), and cleavage of caspase-9, -7, fodrin, and PARP-1 in MCF-7 cells. Inducible ΔNErbB2 expression strongly reduced cisplatin-induced ATM- and p53-phosphorylation, augmented Noxa upregulation and caspase-9 and -7 cleavage, doubled p21(WAF1/Cip1) (CDKN1A) expression, and nearly abolished Bcl-2 expression. LC3-GFP analysis demonstrated that autophagic flux was reduced by cisplatin in a manner augmented by ΔNErbB2, yet did not contribute to cisplatin-induced death. Using knockdown approaches, it was shown that cisplatin-induced caspase-7 cleavage in ΔNErbB2-MCF-7 cells was Noxa- and caspase-9 dependent. This pathway was augmented by NHE1 inhibition, while the Na(+)/HCO3 (-) cotransporter (SLC4A7/NBCn1) was internalized following cisplatin exposure. This work reveals that ΔNErbB2 strongly affects several major pro- and antiapoptotic pathways and provides mechanistic insight into the role of NHE1 in chemotherapy resistance. These findings have relevance for defining therapy regimens in breast cancers with ΔNErbB2 and/or NHE1 overexpression.