Vitamin C increases the apoptosis via up-regulation p53 during cisplatin treatment in human colon cancer cells

Vitamin C (VC) is an important antioxidant and enzyme co-factor that works by stimulating the immune system and protecting against infections. It is well known that melanoma cells are more susceptible to VC than any other tumor cells. However, the role of VC in the treatment of colon cancer has not been studied. Cisplatin (CDDP) is a DNA damaging agent and is widely used for treating cancer, while the role of p53 in CDDP-induced cell death has been stressed. Using cell growth assays, morphological methods, Western blotting, flow cytometry, and DNA fragmentation analysis, we measured the expression of p53 level involved in the effect of VC on CDDP-induced apoptosis of HCT116, a human colon cancer cell line. CDDP plus VC treatment resulted in significantly increased apoptosis along with upregulation of p53 compared to untreated cells and/or CDDP-treated cells. These results suggest that VC enhanced CDDP sensitivity and apoptosis via upregulation of p53.     

Inhibition of autophagy by 3-MA potentiates purvalanol-induced apoptosis in Bax deficient HCT 116 colon cancer cells

The purine-derived analogs, roscovitine and purvalanol are selective synthetic inhibitors of cyclin-dependent kinases (CDKs) induced cell cycle arrest and lead to apoptotic cell death in various cancer cells. Although a number of studies investigated the molecular mechanism of each CDK inhibitor on apoptotic cell death mechanism with their therapeutic potential, their regulatory role on autophagy is not clarified yet. In this paper, our aim was to investigate molecular mechanism of CDK inhibitors on autophagy and apoptosis in wild type (wt) and Bax deficient HCT 116 cells. Exposure of HCT 116 wt and Bax^−/− cells to roscovitine or purvalanol for 24 h decreased cell viability in dose-dependent manner. However, Bax deficient HCT 116 cells were found more resistant against purvalanol treatment compared to wt cells. We also established that both CDK inhibitors induced apoptosis through activating mitochondria-mediated pathway in caspase-dependent manner regardless of Bax expression in HCT 116 colon cancer cells. Concomitantly, we determined that purvalanol was also effective on autophagy in HCT 116 colon cancer cells. Inhibition of autophagy by 3-MA treatment enhanced the purvalanol induced apoptotic cell death in HCT 116 Bax^−/− cells. Our results revealed that mechanistic action of each CDK inhibitor on cell death mechanism differs. While purvalanol treatment activated apoptosis and autophagy in HCT 116 cells, roscovitine was only effective on caspase-dependent apoptotic pathway. Another important difference between two CDK inhibitors, although roscovitine treatment overcame Bax-mediated drug resistance in HCT 116 cells, purvalanol did not exert same effect.     

The α-mangostin prevention on cisplatin-induced apoptotic death in LLC-PK1 cells is associated to an inhibition of ROS production and p53 induction

Cisplatin (CDDP) is a widely useful chemotherapeutic agent for the treatment of tumors including lung, ovary and testis. Acute renal injury, however, is the main side effect observed after CDDP treatment. This side effect is related to the apoptotic death in proximal tubular cells in the kidney and p53 protein has a central role in this process. On the other hand, α-mangostin (α-M), a xanthone derived from the pericarp of mangosteen, exerts a renoprotective effect against cisplatin-induced renal damage in rats. The aim of this study was to evaluate whether α-M protects proximal tubule renal epithelial cells (LLC-PK1) from CDDP-induced apoptotic death. Cells were co-incubated with 5 μM α-M and 100 μM CDDP for 24 h. It was found that α-M attenuated the following alterations: the apoptotic cell death, the increase in reactive oxygen species (ROS), the glutathione depletion and the increase in p53 expression induced by CDDP. In conclusion, the preventive effect of α-M on CDDP-induced apoptotic death is associated to the inhibition of p53 expression and ROS generation.     

A combination of cilostazol and Ginkgo biloba extract protects against cisplatin-induced Cochleo-vestibular dysfunction by inhibiting the mitochondrial apoptotic and ERK pathways

Cisplatin (cis-diammine-dichloroplatinum; CDDP) is an anticancer drug that induces significant hearing loss and balance dysfunction as side effects. Cilostazol (CS, 6-[4-(1-cyclohexyl-1H-tetrazol-5-yl) butoxy]-3, 4-dihydro-2-(1H)-quinolinone) has neuroprotective and antioxidant effects, whereas Ginkgo biloba extract (GbE) has preventive effects on CDDP-induced hearing loss in rats, and GbE enhances the antiatherogenic effect of CS by inhibiting the generation of reactive oxygen species (ROS). The purpose of this study was to investigate the effects of renexin (RXN), which contains GbE and CS, against CDDP-induced cochleo-vestibular dysfunction in rats and to elucidate the mechanism underlying the protective effects of RXN on auditory cells. Rats intraperitoneally injected with CDDP exhibited an increase in hearing threshold and vestibular dysfunction, which agreed with hair cell damage in the Organ of Corti and otoliths. However, these impairments were significantly prevented in a dose-dependent manner by pre- and co-treatment with RXN, and these preventive effects in RXN-treated rats were more prominent than those in GbE-treated rats. In a CDDP pharmacokinetic study, platinum concentration was very similar between CDDP-only treated and RXN+CDDP cotreated rats. RXN markedly attenuated CDDP-induced intracellular ROS and significantly reduced CDDP-activated expression of p-extracellular regulated kinase (ERK), BAX, cytochrome c, cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase, but increased BCL-XL expression. These results show that RXN may have a synergistic effect by strongly protecting hearing and vestibular dysfunction induced by CDDP by inhibiting ROS production, mitochondrial pathways and the ERK pathway, without interfering with CDDP pharmacokinetics. Therefore, RXN could potentially be used to reduce CDDP-related hearing loss and dizziness.     

Snake venom toxin from Vipera lebetina turanica sensitizes cancer cells to TRAIL through ROS- and JNK-mediated upregulation of death receptors and downregulation of survival proteins

We investigated whether snake venom toxin (SVT) from Vipera lebetina turanica enhances the apoptosis ability of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) in cancer cells. TRAIL inhibited HCT116 cell growth in a dose-dependent manner; however, this reduction did not occur in TRAIL resistant HT-29, A549 and HepG2 cells with an even higher dose of TRAIL. SVT, but not TRAIL enhanced expression of cell death receptor (DR) in TRAIL resistant cancer cells in a dose-dependent manner. A combination of SVT with TRAIL significantly inhibited cell growth of TRAIL resistant HT-29, A549 and HepG2 cells. Consistent with cell growth inhibition, the expression of TRAIL receptors; DR4 and DR5 was significantly increased as well as apoptosis related proteins such as cleaved caspase-3, -8, -9 and Bax. However, the expression of survival proteins (e.g., cFLIP, survivin, XIAP and Bcl2) was suppressed by the combination treatment of SVT and TRAIL. Depletion of DR4 or DR5 by small interfering RNA significantly reversed the cell growth inhibitory and apoptosis blocking effects of SVT in HCT116 and HT-29 cells. Pretreatment with the c-Jun N-terminal kinase (JNK) inhibitor SP600125 and the reactive oxygen species (ROS) scavenger N-acetylcysteine reduced the SVT and TRAIL-induced upregulation of DR4 and DR5 expression, expression of the apoptosis related protein such as caspase-3 and-9, as well as cell growth inhibitory effects. The collective results suggest that SVT facilitates TRAIL-induced apoptosis in cancer cells through up-regulation of the TRAIL receptors; DR4 and DR5 via ROS/JNK pathway signals.     

Generation of ROS by CAY10598 leads to inactivation of STAT3 signaling and induction of apoptosis in human colon cancer HCT116 cells

Abstract

Prostaglandin E₂ (PGE₂) has been reported to play critical roles in cell fate decision by interacting with four types of prostanoid receptors such as EP1, EP2, EP3 and EP4. The present study was aimed at investigating the effect of the EP4-specific agonist CAY10598 in human colon cancer HCT116 cells. Our study revealed that treatment with CAY10598 significantly reduced the cell viability and induced apoptosis in HCT116 cells, as evidenced by the induction of p53 and Bax, release of cytochrome c, cleavage of caspase-9, -7, and -3, and PARP, and the inhibition of Bcl-2, Bcl-xL and survivin expression. Moreover, treatment with CAY10598 diminished the phosphorylation of JAK2, leading to the attenuation of STAT3 activation in HCT116 cells. CAY10598-induced apoptosis in cells which were transiently transfected with EP4 siRNA or treated with an EP4 antagonist prior to incubation with the compound remained unaffected, suggesting an EP4-independent mechanism of apoptosis induction by CAY10598. We found that treatment with CAY10598 generated reactive oxygen species (ROS) and pretreatment of cells with N-acetyl cysteine rescued cells from apoptosis by abrogating the inhibitory effect of CAY10598 on the activation of JAK2/STAT3 signaling. In conclusion, CAY10598 induced apoptosis in HCT116 cells in an EP4-independent manner, but through the generation of ROS and inactivation of JAK2/STAT3 signaling.     

Beclin 1 augmented cis-diamminedichloroplatinum induced apoptosis via enhancing caspase-9 activity

Beclin 1, identified as a Bcl-2-interacting protein, is known to enhance autophagy. However, the effect of Beclin 1 on apoptotic signaling has remained unclear. Here, we show that overexpression of Beclin 1 in MKN28 human gastric cancer cells augmented cis-diamminedichloroplatinum (CDDP)-induced apoptosis. Conversely, "knockdown" of Beclin 1 by a small inhibitory RNA in MKN 1 cells attenuated this cytotoxicity. Furthermore, not only caspase-3/7 activities, but also caspase-9 activity was increased in Beclin 1 gene transfectants treated with CDDP, and caspase-9 inhibitor completely abolished augmentation of CDDP-induced apoptosis by Beclin 1 as did a caspase-3 inhibitor. Thus, Beclin 1 augments CDDP-induced apoptosis through enhancing caspase-9 activity and functions as a pro-apoptotic molecule.     

Scavenging activity of indole compounds against cisplatin-induced reactive oxygen species

The antioxidant effects of indole compounds such as melatonin (MLT), tryptophan, and serotonin, on cisplatin (cis-diaminedichloroplatinum, or CDDP)-induced reactive oxygen species (ROS) generation were examined by electron spin resonance (ESR). In addition, DNA fragmentation by CDDP-induced ROS and the effect of MLT on it were analyzed in primary cultures of rat renal tubular epithelial cells. MLT and serotonin had scavenging effects on CDDP-induced hydroxy radicals (*OH), and the scavenging activity of MLT was higher than that of serotonin. The exposure of primary-cultured renal tubular cells to CDDP caused severe cytotoxicity. Tryptophan, serotonin, and 6-OH-MLT did not reduce the CDDP-induced cytotoxicity, whereas MLT did. CDDP exposure induced DNA fragmentation in primary-cultured renal tubular cells, but the simultaneous administration of MLT inhibited the DNA fragmentation. These results indicate that MLT inhibits CDDP-induced cytotoxicity by directly scavenging *OH, and that MLT markedly reduces renal cytotoxicity and DNA fragmentation caused by CDDP-induced ROS in vitro.     

Polyamine depletion enhances the roscovitine-induced apoptosis through the activation of mitochondria in HCT116 colon carcinoma cells

Small molecule inhibitors of cyclin-dependent kinases (CDKs) show high therapeutic potential in various cancer types which are characterized by the accumulation of transformed cells due to impaired apoptotic machinery. Roscovitine, a CDK inhibitor showed to be a potent apoptotic inducer in several cancer cells. Polyamines, putrescine, spermidine and spermine, are biogenic amines involved in many cellular processes, including apoptosis. In this study, we explored the potential role of polyamines in roscovitine-induced apoptosis in HCT116 colon cancer cells. Roscovitine induced apoptosis by activating mitochondrial pathway caspases and modulating the expression of Bcl-2 family members. Depletion of polyamines by treatment with difluoromethylornithine (DFMO) increased roscovitine-induced apoptosis. Transient silencing of ornithine decarboxylase, polyamine biosynthesis enzyme and special target of DFMO also increased roscovitine-induced apoptosis in HCT116 cells. Interestingly, additional putrescine treatment was found pro-apoptotic due to the presence of non-functional ornithine decarboxylase (ODC). Finally, roscovitine altered polyamine catabolic pathway and led to decrease in putrescine and spermidine levels. Therefore, the metabolic regulation of polyamines may dictate the power of roscovitine induced apoptotic responses in HCT116 colon cancer cells.     

Gangliosides induce cell apoptosis in the cytotoxic line CTLL-2, but not in the promyelocyte leukemia cell line HL-60

Gangliosides induce apoptosis in the cells of the IL-2-dependent cytotoxic mouse line CTLL-2. Upon incubation with gangliosides for 24 h, their effect resulting in appearance of apoptotic cells, falls in a series GM2 > GM3 > GM1 > GD1a > GD1b > GT1b. In the presence of rIL-2, apoptosis induced by GM1 is suppressed, whereas that induced by GM2 is enhanced (the effect of intracellular agent C2-Cer is independent of this cytokine). The GM1-induced apoptosis is cancelled by the caspase I inhibitor. The gangliosides under study are not able to induce apoptosis in the promyelocyte leukemia cell line HL-60. Physiological aspects of the phenomenon found are discussed.     

p53 Is Required for Cisplatin-induced Processing of the Mitochondrial Fusion Protein L-Opa1 That Is Mediated by the Mitochondrial Metallopeptidase Oma1 in Gynecologic Cancers

Mitochondria are highly dynamic organelles, and mitochondrial fission is a crucial step of apoptosis. Although Oma1 is believed to be responsible for long form Opa1 (L-Opa1) processing during mitochondrial fragmentation, whether and how Oma1 is involved in L-Opa1 processing and participates in the regulation of chemoresistance is unknown. Chemosensitive and chemoresistant ovarian (OVCA) and cervical (CECA) cancer cells were treated with cisplatin (CDDP). Mitochondrial dynamics and protein contents were assessed by immunofluorescence and Western blot, respectively. The requirements of Oma1 and p53 for CDDP-induced L-Opa1 processing, mitochondrial fragmentation, and apoptosis were examined by siRNA or cDNA. CDDP induces L-Opa1 processing and mitochondrial fragmentation in chemosensitive but not in chemoresistant cells. CDDP induced Oma1 40-kDa form increases in OV2008 cells, not in C13* cells. Oma1 knockdown inhibited L-Opa1 processing, mitochondrial fragmentation, and apoptosis. Silencing p53 expression attenuated the effects of CDDP in Oma1 (40 kDa) increase, L-Opa1 processing, mitochondrial fragmentation, and apoptosis in chemosensitive OVCA cells, whereas reconstitution of p53 in p53 mutant or null chemoresistant OVCA cells induced Oma1 (40 kDa) increase, L-Opa1 processing, mitochondrial fragmentation, and apoptosis irrespective of the presence of CDDP. Prohibitin 1 (Phb1) dissociates from Opa1-Phb1 complex and binds phosphorylated p53 (serine 15) in response to CDDP in chemosensitive but not chemoresistant CECA cells. These findings demonstrate that (a) p53 and Oma1 mediate L-Opa1 processing, (b) mitochondrial fragmentation is involved in CDDP-induced apoptosis in OVCA and CECA cells, and (c) dysregulated mitochondrial dynamics may in part be involved in the pathophysiology of CDDP resistance.     

Role of p21 in apoptosis and senescence of human colon cancer cells treated with camptothecin

Treatment of cells with the anti-cancer drug camptothecin (CPT) induces topoisomerase I (Top1)-mediated DNA damage, which in turn affects cell proliferation and survival. In this report, we demonstrate that treatment of the wild-type HCT116 (wt HCT116) human colon cancer cell line and the isogenic p53(-/-) HCT116 and p21(-/-) HCT116 cell lines with a high concentration (250 nm) of CPT resulted in apoptosis, indicating that apoptosis occurred by a p53- and p21-independent mechanism. In contrast, treatment with a low concentration (20 nm) of CPT induced cell cycle arrest and senescence of the wt HCT116 cells, but apoptosis of the p53(-/-) HCT116 and p21(-/-) HCT116 cells. Further investigations indicated that p53-dependent expression of p21 blocked apoptosis of wt HCT116 cells treated with 20 nm, but not 250 nm CPT. Interestingly, blocking of the apoptotic pathway, by Z-VAD-FMK, in p21(-/-) HCT116 cells following treatment with 20 nm CPT did not permit the cells to develop properties of senescence. These observations demonstrated that p21 was required for senescence development of HCT116 cells following treatment with low concentrations of CPT.     

Butyrate-induced apoptosis in HCT116 colorectal cancer cells includes induction of a cell stress response

Short chain fatty acids (SCFA), principally butyrate, propionate, and acetate, are produced in the gut through the fermentation of dietary fiber by the colonic microbiotica. Butyrate in particular is the preferred energy source for the cells in the colonic mucosa and has been demonstrated to induce apoptosis in colorectal cancer cell lines. We have used proteomics, specifically 2D-DIGE and mass spectrometry, to identify proteins involved in butyrate-induced apoptosis in HCT116 cells and also to identify proteins involved in the development of butyrate insensitivity in its derivative, the HCT116-BR cells. The HCT116-BR cell line was characterized as being less responsive to the apoptotic effects of butyrate in comparison to its parent cell line. Our analysis has revealed that butyrate likely induces a cellular stress response in HCT116 cells characterized by p38 MAPK activation and an endoplasmic reticulum (ER) stress response, resulting in caspase 3/7 activation and cell death. Adaptive cellular responses to stress-induced apoptosis in HCT116-BR cells may be responsible for the development of resistance to apoptosis in this cell line. We also report for the first time additional cellular processes altered by butyrate, such as heme biosynthesis and dysregulated expression of nuclear lamina proteins, which may be involved in the apoptotic response observed in these cell lines.     

Production of multiple brain-like ganglioside species is dispensable for fas-induced apoptosis of lymphoid cells

Activation of an acid sphingomyelinase (aSMase) leading to a biosynthesis of GD3 disialoganglioside has been associated with Fas-induced apoptosis of lymphoid cells. The present study was undertaken to clarify the role of this enzyme in the generation of gangliosides during apoptosis triggered by Fas ligation. The issue was addressed by using aSMase-deficient and aSMase-corrected cell lines derived from Niemann-Pick disease (NPD) patients. Fas cross-linking elicited a rapid production of large amounts of complex a- and b-series species of gangliosides with a pattern and a chromatographic behavior as single bands reminiscent of brain gangliosides. The gangliosides were synthesized within the first ten minutes and completely disappeared within thirty minutes after stimulation. Noteworthy is the observation that GD3 was not the only ganglioside produced. The production of gangliosides and the onset of apoptotic hallmarks occurred similarly in both aSMase-deficient and aSMase-corrected NPD lymphoid cells, indicating that aSMase activation is not accountable for ganglioside generation. Hampering ganglioside production by inhibiting the key enzyme glucosylceramide synthase did not abrogate the apoptotic process. In addition, GM3 synthase-deficient lymphoid cells underwent Fas-induced apoptosis, suggesting that gangliosides are unlikely to play an indispensable role in transducing Fas-induced apoptosis of lymphoid cells.     

Proline oxidase, a proapoptotic gene, is induced by troglitazone: evidence for both peroxisome proliferator-activated receptor gamma-dependent and -independent mechanisms

Proline oxidase (POX) is a redox enzyme localized in the mitochondrial inner membrane. We and others have shown that POX is a p53-induced gene that can mediate apoptosis through generation of reactive oxygen species (ROS). The peroxisome proliferator-activated receptor gamma (PPARgamma) ligand troglitazone was found to activate the POX promoter in colon cancer cells. PPARgamma ligands have been reported to induce apoptosis in a variety of cancer cells. In HCT116 cells expressing a wild-type PPARgamma, troglitazone enhanced the binding of PPARgamma to PPAR-responsive element in the POX promoter and increased endogenous POX expression. Blocking of PPARgamma activation either by antagonist GW9662 or deletion of PPAR-responsive element in the POX promoter only partially decreased the POX promoter activation in response to troglitazone, indicating also the involvement of PPARgamma-independent mechanisms. Further, troglitazone also induced p53 protein expression in HCT116 cells, which may be the possible mechanism for PPARgamma-independent POX activation, since POX has been shown to be a downstream mediator in p53-induced apoptosis. In HCT15 cells, with both mutant p53 and mutant PPARgamma, there was no effect of troglitazone on POX activation, whereas in HT29 cells, with a mutant p53 and wild type PPARgamma, increased activation was observed by ligand stimulation, indicating that both PPARgamma-dependent and -independent mechanisms are involved in the troglitazone-induced POX expression. A time- and dose-dependent increase in POX catalytic activity was obtained in HCT116 cells treated with troglitazone with a concomitant increase in the production of intracellular ROS. Our results suggest that the induction of apoptosis by troglitazone may, at least in part, be mediated by targeting POX gene expression for generation of ROS by POX both by PPARgamma-dependent and -independent mechanisms.     

Bak compensated for Bax in p53-null cells to release cytochrome c for the initiation of mitochondrial signaling during Withanolide D-induced apoptosis

The goal of cancer chemotherapy to induce multi-directional apoptosis as targeting a single pathway is unable to decrease all the downstream effect arises from crosstalk. Present study reports that Withanolide D (WithaD), a steroidal lactone isolated from Withania somnifera, induced cellular apoptosis in which mitochondria and p53 were intricately involved. In MOLT-3 and HCT116p53+/+ cells, WithaD induced crosstalk between intrinsic and extrinsic signaling through Bid, whereas in K562 and HCT116p53-/- cells, only intrinsic pathway was activated where Bid remain unaltered. WithaD showed pronounced activation of p53 in cancer cells. Moreover, lowered apoptogenic effect of HCT116p53-/- over HCT116p53+/+ established a strong correlation between WithaD-mediated apoptosis and p53. WithaD induced Bax and Bak upregulation in HCT116p53+/+, whereas increase only Bak expression in HCT116p53-/- cells, which was coordinated with augmented p53 expression. p53 inhibition substantially reduced Bax level and failed to inhibit Bak upregulation in HCT116p53+/+ cells confirming p53-dependent Bax and p53-independent Bak activation. Additionally, in HCT116p53+/+ cells, combined loss of Bax and Bak (HCT116Bax-Bak-) reduced WithaD-induced apoptosis and completely blocked cytochrome c release whereas single loss of Bax or Bak (HCT116Bax-Bak+/HCT116Bax+Bak-) was only marginally effective after WithaD treatment. In HCT116p53-/- cells, though Bax translocation to mitochondria was abrogated, Bak oligomerization helped the cells to release cytochrome c even before the disruption of mitochondrial membrane potential. WithaD also showed in vitro growth-inhibitory activity against an array of p53 wild type and null cancer cells and K562 xenograft in vivo. Taken together, WithaD elicited apoptosis in malignant cells through Bax/Bak dependent pathway in p53-wild type cells, whereas Bak compensated against loss of Bax in p53-null cells.     

Apoptin induces pyroptosis of colorectal cancer cells via the GSDME-dependent pathway

Apoptin is a small molecular weight protein encoded by the VP3 gene of chicken anemia virus (CAV). It can induce apoptosis of tumor cells and play anti-tumorigenic functions. In this study, we identified a time-dependent inhibitory role of apoptin on the viability of HCT116 cells. We also demonstrated that apoptin induces pyroptosis through cleaved caspase 3, and with a concomitant cleavage of gasdermin E (GSDME) rather than GSDMD. GSDME knockdown switched the apoptin-induced cell death from pyroptosis to apoptosis in vitro. Furthermore, we demonstrated that the effect of apoptin on GSDME-dependent pyroptosis could be mitigated by caspase-3 and caspase-9 siRNA knockdown. Additionally, apoptin enhanced the intracellular reactive oxygen species (ROS), causing aggregation of the mitochondrial membrane protein Tom20. Moreover, bax and cytochrome c were released to the activating caspase-9, eventually triggering pyroptosis. Therefore, GSDME mediates the apoptin-induced pyroptosis through the mitochondrial apoptotic pathway. Finally, using nude mice xenografted with HCT116 cells, we found that apoptin induces pyroptosis and significantly inhibits tumor growth. Based on this mechanism, apoptin may provide a new strategy for colorectal cancer therapy.     

Nitric oxide confers cisplatin resistance in human lung cancer cells through upregulation of aldo-keto reductase 1B10 and proteasome

Abstract

In this study, we show that exposure of human lung cancer A549 cells to cisplatin (cis-diamminedichloroplatinum, CDDP) promotes production of nitric oxide (NO) through generation of reactive oxygen species (ROS) and resulting upregulation of inducible NO synthase (iNOS). The incubation of the cells with a NO donor, diethylenetriamine NONOate, not only reduced the CDDP-induced cell death and apoptotic alterations (induction of CCAAT-enhancer-binding protein homologous protein and caspase-3 activation), but also elevated proteolytic activity of 26S proteasome, suggesting that the activation of proteasome function contributes to the reduction of CDDP sensitivity by NO. Monitoring expression levels of six aldo-keto reductases (AKRs) (1A1, 1B1, 1B10, 1C1, 1C2, and 1C3) during the treatment with the NO donor and subsequent CDDP sensitivity test using the specific inhibitors also proposed that upregulation of AKR1B10 by NO is a key process for acquiring the CDDP resistance in A549 cells. Treatment with CDDP and NO increased amounts of nitrotyrosine protein adducts, indicative of peroxynitrite formation, and promoted the induction of AKR1B10, inferring a relationship between peroxynitrite formation and the enzyme upregulation in the cells. The treatment with CDDP or a ROS-related lipid aldehyde, 4-hydroxy-2-nonenal, facilitated the iNOS upregulation, which was restored by increasing the AKR1B10 expression. In contrast, the facilitation of NO production by CDDP treatment was hardly observed in AKR1B10-overexpressing A549 cells and established CDDP-resistant cancer cells (A549, LoVo, and PC3). Collectively, these results suggest the NO functions as a key regulator controlling AKR1B10 expression and 26S proteasome function leading to gain of the CDDP resistance.