Chemotherapeutic Agent-induced Apoptosis Research Articles

Crotonylated BEX2 interacts with NDP52 and enhances mitophagy to modulate chemotherapeutic agent-induced apoptosis in non-small-cell lung cancer cells

Brain expressed X-linked gene 2 (BEX2) encoded protein was originally identified to promote transcription by interacting with several transcription factors in the DNA–binding complexes. Recently, BEX2 was found to be localized in cytosol and/or mitochondria and regulate apoptosis in cancer cells and tumor growth. However, the molecular mechanism underlying its roles in cancer cells remains unclear. Here, we report that crotonylated BEX2 plays an important role in inhibiting chemotherapeutic agent-induced apoptosis via enhancing mitophagy in human lung cancer cells. BEX2 promotes mitophagy by facilitating interaction between NDP52 and LC3B. Moreover, BEX2 crotonylation at K59 is critical in the BEX2-mediated mitophagy in lung cancer cells. The K59R mutation of BEX2 inhibits mitophagy by affecting the interaction of NDP52 and LC3B. BEX2 expression is elevated after anticancer drug treatment, and its overexpression inhibits chemotherapy-induced apoptosis. In addition, inhibition of BEX2-regulated mitophagy sensitizes tumor cells to apoptosis. Furthermore, BEX2 promotes tumor growth and inhibits apoptosis by regulating mitophagy in vivo. We also confirm that BEX2 is overexpressed in lung adenocarcinoma and is associated with poor prognosis in lymph node metastasis-free cancer. Therefore, combination treatment with pharmaceutical approaches targeting BEX2-induced mitophagy and anticancer drugs may represent a potential strategy for NSCLC therapy.

Shift in MSL1 alternative polyadenylation in response to DNA damage protects cancer cells from chemotherapeutic agent-induced apoptosis.

SUMMARYDNA damage reshapes the cellular transcriptome by modulating RNA transcription and processing. In cancer cells, these changes can alter the expression of genes in the immune surveillance and cell death pathways. Here, we investigate how DNA damage impacts alternative polyadenylation (APA) using the PAPERCLIP technique. We find that APA shifts are a coordinated response for hundreds of genes to DNA damage, and we identify PCF11 as an important contributor of DNA damage-induced APA shifts. One of these APA shifts results in upregulation of the full-length MSL1 mRNA isoform, which protects cells from DNA damage-induced apoptosis and promotes cell survival from DNA-damaging agents. Importantly, blocking MSL1 upregulation enhances cytotoxicity of chemotherapeutic agents even in the absence of p53 and overcomes chemoresistance. Our study demonstrates that characterizing adaptive APA shifts to DNA damage has therapeutic implications and reveals a link between PCF11, the MSL complex, and DNA damage-induced apoptosis.

Protumor role of estrogen receptor expression in oral squamous cell carcinoma cells

Accumulating evidence has demonstrated the protumor role of estrogen receptor (ER)-mediated signaling in multiple cancer types, which is distinct from this signaling in sex steroid-dependent organs. However, its role in oral squamous cell carcinoma (OSCC) remains unclear. We assessed the expression of ERα and ERβ in human OSCC tissues by immunohistochemistry and evaluated the expression of both receptors in OSCC cell lines by immunoblotting and flow cytometry. To further assess the contribution of ER-mediated signals to oral cancer progression, proliferation, invasion, and chemosensitivity, cell lines were stimulated with the ER agonist β-estradiol. Immunohistochemical analysis of OSCC tissues showed that ERβ was present in the cytoplasm and nuclei of OSCC cells. In contrast, ERα was not detected in any of the cases analyzed. Additionally, the proliferation and invasiveness of OSCC cells were significantly elevated following stimulation with β-estradiol. Chemotherapeutic agent-induced apoptosis of cancer cells was attenuated by pretreatment with β-estradiol. ER-mediated signaling plays a crucial role in oral cancer progression by facilitating the proliferation, invasion, and chemoresistance of OSCC cells, indicating its potential for developing novel targeted therapies for this type of cancer.

Regulating Mitochondrial pH with Light and Implications for Chemoresistance.

Chemoresistance is one of the major challenges for cancer treatment, more recently ascribed to defective mitochondrial outer membrane permeabilization (MOMP), significantly diminishing chemotherapeutic agent-induced apoptosis. A boron-dipyrromethene (BODIPY) chromophore-based triarylsulfonium photoacid generator (BD-PAG) was used to target mitochondria with the aim to regulate mitochondrial pH and further depolarize the mitochondrial membrane. Cell viability assays demonstrated the relative biocompatibility of BD-PAG in the dark while live cell imaging suggested high accumulation in mitochondria. Specific assays indicated that BD-PAG is capable of regulating mitochondrial pH with significant effects on mitochondrial membrane depolarization. Therapeutic tests using chlorambucil in combination with BD-PAG revealed a new strategy in chemoresistance suppression.

CD9 blockade suppresses disease progression of high-risk pediatric B-cell precursor acute lymphoblastic leukemia and enhances chemosensitivity.

CD9 has been implicated in cancer progression but its prognostic relevance and therapeutic potential in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) are largely unknown. In a cohort of pediatric BCP-ALL patients, we found that CD9+ cases had a significantly lower 5-year relapse-free survival rate than CD9- cases. Multivariate analysis demonstrated that CD9 positivity independently predicted inferior survival outcomes, and could be applied with established prognostic features, including prednisone response and cytogenetic status, to refine patient stratification. Administration of CD9 antibody substantially suppressed disease progression in NOD/SCID mice xenografted with CD9+ cell lines and primary leukemic blasts from patients with high-risk and refractory BCP-ALL, without compromising hematopoietic stem cell engraftment. Combination of anti-CD9 with conventional chemotherapy further reduced leukemic burden and prolonged animal survival. Mechanistically, CD9 blockade inhibited leukemic cell proliferation, induced G0/G1 cell cycle arrest, activated p38, and enhanced chemotherapeutic agent-induced apoptosis. Further, CD9 physically interacted with integrin very late antigen-4, regulated affinity to vascular cell adhesion molecule-1, and was involved in leukemia-stroma interaction. Collectively, our study established CD9 as a new prognostic marker, validated the preclinical efficacy of CD9 antibody, and laid the foundation for clinical development of CD9-targeted therapy for high-risk and refractory pediatric BCP-ALL.

Inhibition of autophagy in hepatocarcinoma cells promotes chemotherapeutic agent-induced apoptosis during nutrient deprivation.

Autophagy is a lysosome-dependent process involved in protein and organelle degradation. It has been suggested that autophagy is activated in nutrient-deficient condition and plays an important role in protecting cells from nutrient shortage. However, the effect of autophagy on chemotherapy during nutrient deficiency has been rarely researched. In the present study, we discovered that hepatocarcinoma cells exhibit chemoinsensitivity accompanied by the activation of autophagy when cultured in nutrient-deprived medium. Inhibition of autophagy by 3-methyladenine or siRNA‑targeted Beclin1 increased the nutrient deprivation‑induced apoptosis and chemosensitivity in hepatocarcinoma cells. Furthermore, decreased mitochondrial mass was detected when cells underwent autophagy. The present study suggests that induction of autophagy confers a survival advantage for hepatocarcinoma cells during nutrient deprivation, not only rescuing cells from nutrient deficiency-induced cell apoptosis, but also protecting cells from chemotherapy-induced cell death. Combined usage of the inhibition of autophagy and conventional chemotherapeutic agents could be an effective therapy for hepatocarcinoma during nutrient deprivation.

Small interfering RNA (siRNA) against Slug induces apoptosis and sensitizes human anaplastic thyroid carcinoma cells to doxorubicin.

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human cancers and often shows resistance to multimodal therapeutic approaches. It has been shown that the transcriptional repressor Slug inhibits the chemotherapeutic agent-induced apoptosis of cancer cells. We evaluated whether targeting of Slug could augment doxorubicin (DOX)-induced apoptosis of ATC cells. We also determined changes in PUMA (p53-upregulated modulator of apoptosis) expression levels to identify possible mechanisms of their combined actions. SW1736 cells were transfected with Slug siRNA or/and PUMA siRNA and then exposed to DOX (0.1, 1, and 5 μ M) for selected times. Scrambled siRNA was used as a control. The effects on cell viability were determined via MTT assay. Apoptosis was assessed using TUNEL assays and annexin V staining, and was confirmed by flow cytometry analyses. Slug and PUMA levels were determined using western blotting, RT-PCR and immunofluorescence analyses. We used a subcutaneous implanted tumor model of SW1736 cells in nude mice to assess the effects of Slug silencing in combination with DOX on tumor development. Apoptosis was assessed via TUNEL assay. Targeting of Slug using siRNA inhibits growth of SW1736 cells and sensitizes SW1736 cells to DOX in vitro and vivo. Targeting of Slug combined with DOX led to lower cell viability than treatment with DOX alone in SW1736 cells. TUNEL and flow cytometry analyses showed that targeting of Slug enhanced DOX-induced apoptosis of SW1736 cells. In addition, targeting of Slug increased PUMA expression, and targeting of PUMA restored the chemoresistance of SW1736/Slug siRNA cells to DOX. Knockdown of Slug enhanced the antitumor activity of DOX in SW1736 cells via induction of PUMA upregulation. Our results suggest that targeting of Slug has good potential for the development of new therapeutic strategies for ATC.

Tumor suppressor BLU promotes TRAIL-induced apoptosis by downregulating NF-κB signaling in nasopharyngeal carcinoma

A putative tumor suppressor BLU mapped on the chromosomal 3p21 region, is frequently lost in human tumors including nasopharyngeal carcinoma (NPC). To explore the underlying mechanism of tumor suppression by BLU, its potential to promote apoptosis induced by TRAIL, an effector molecule elaborated by natural killer-T (NKT) cells was investigated. BLU was re-expressed in NPC-derived HNE1 cells by recombinant adenoviral infection and the cells were challenged with recombinant TRAIL. The growth inhibition of BLU was assayed and apoptosis was examined by flow cytometry-based tetramethylrhodamine ethyl ester (TMRE) and annexin V staining, cleavage of pro-caspase-8 and poly ADP ribose polymerase (PARP). The modulation of NF-κB pathway by BLU was evaluated by the reporter activity and estimation of the level of the molecules involved such as IKKalpha, p65 NF-κB, as well as NF-κB induced anti-apoptotic factors cFLIPL and cIAP2. The expression of BLU exerted in vitro and in vivo growth inhibitory effect and promoted TRAIL-induced apoptosis. This phenomenon was validated by FACS-based assays of mitochondrial membrane potential (BLU vs. Vector 87.8% ± 7.7% and 72.1%±6.7% at 6h exposure to TRAIL) and phosphatidylserine turnover (BLU vs. vector: 28.7%±2.9% and 22.6%±2.5%), as well as, enhanced caspapse-8 cleavage. Similar with the findings that BLU promotes chemotherapeutic agent-induced apoptosis, it also augmented death receptor-induced pathway through NF-κB pathway inhibition. In conclusion, BLU suppressed tumor formation by strengthening the antitumor immunity.

Low dose of arsenic trioxide inhibits multidrug resistant-related P-glycoprotein expression in human neuroblastoma cell line.

This study investigated arsenic trioxide(As2O3), cisplatin (DDP) and etoposide (Vp16) on the anticancer effects and P-glycoprotein(P-gp) expression in neuroblastoma(NB) SK-N-SH cells. The potential influence of As2O3, DDP and Vp16 currently included in NB routine treatment protocols on cytotoxicity in SK-N-SH cells was measured by flow cytometry and drug half-maximal inhibitory concentration (IC50) was established. Moreover, chemotherapeutic agent-mediated changes of cellular expression levels of resistant-related P-gp, was monitored using western blotting. The data showed that As2O3, DDP and Vp16 significantly inhibited the growth and survival of the SK-N-SH cells at different concentration. Notably, the levels of apoptosis were upregulated in SK-N-SH cells with an acceleration of the exposure time and the concentration of As2O3, DDP and Vp16. As2O3, DDP and Vp16 were observed with their IC50 values on SK-N-SH cells being 3µM, 8and 100µg/ml, respectively. Flow cytometry analysis showed that As2O3 at low concentrations in SK-N-SH cells led to enhanced accumulation of cell populations in G2/M phase with increasing the exposure time, and increased levels of apoptosis. In contrast, we observed that SK-N-SH cell populations arrested in Sphase by DDP and Vp16. In vitro examination revealed that following pretreatment of SK-N-SH cells with As2O3, the expression of P-gp was not increased. The expression of P-gp downregulation were noted following the group treated by As2O3 at 2 and 3µM. Exposed to As2O3 at 3µM for 72h, SK-N-SH cells exhibited lower expression of P-gp than 2µM As2O3 for 72h. In contrast, the expression of P-gp was upregulated by DDP and VP16. In summary, SK-N-SH cells were responsive to chemotherapeutic agent-induced apoptosis in a dose-dependent and time-dependent manner. In particular, ours findings showed that low dose of As2O3 markedly reduced the P-gp expression and increased apoptotic cell death in human NB cell line.

MicroRNA-374b Suppresses Proliferation and Promotes Apoptosis in T-cell Lymphoblastic Lymphoma by Repressing AKT1 and Wnt-16.

Deregulation of microRNA (miRNA) has been extensively investigated in both Hodgkin and non-Hodgkin lymphomas (NHL); however, little is known about the roles of miRNAs in T-cell lymphoblastic lymphoma (T-LBL). The aim of the present study was to investigate the potential roles of miR-374b in the development and treatment of T-LBL. MiRCURY LNA array was used to generate a miRNA-expressing profile. Real-time quantitative PCR and immunohistochemistry (IHC) were applied to detect the expression of miR-374b, AKT1, and Wnt16 in T-LBL samples. The dual-luciferase reporter assay was conducted to confirm target associations of miR-374b. The tumor-suppressive effect of miR-374b was determined by both in vitro and in vivo studies. The expression of 380 miRNAs was evaluated in five human T-LBL tissues and five infantile thymus samples by microRNA microarrays. Downregulation of miR-374b was frequently detected in primary T-LBL tissues, which was significantly associated with worse overall survival and increased risk of recurrence of the 58 patients enrolled in this study. miR-374b suppressed T-LBL cell proliferation in vitro and in vivo and sensitized cells to serum starvation- and chemotherapeutic agent-induced apoptosis. Furthermore, we characterized two AKT pathway-associated molecules, AKT1 and Wnt16, as direct targets of miR-374b. Consistently, in T-LBL patient tissues, AKT1 and Wnt16 expression was inversely correlated with miR-374b levels, and was an independent predictor of recurrence and survival. Our data highlight the molecular etiology and clinical significance of miR-374b in T-LBL. Targeting miR-374b may represent a new therapeutic strategy to improve therapy and survival for T-LBL patients.

Microrna-374b Suppresses Proliferation and Promotes Apoptosis in T-Cell Lymphoblastic Lymphoma By Repressing Wnt-16 and AKT1 and Is a Promising Predictive Biomarker for Patients Survival

Background: De-regulation of microRNA (miRNA) has been extensively investigated in both Hodgkin (HL) and non-Hodgkin lymphomas (NHL), however, little is known about the roles of miRNAs in T-cell lymphoblastic lymphoma (T-LBL). To understand the involvement of miRNAs in the development and treatment of (T-LBL), miRNA profiles were compared between tumor and corresponding non-tumor tissues.Methods: miRCURY LNA array was used to generate miRNA expressing profile. Real-time quantitative PCR and immunohistochemistry (IHC) were applied to detect the expression of miR-374b, AKT1 and Wnt16 in T-LBL samples. Dual-luciferase reporter assay was conducted to confirm target associations of miR-374b. The tumor suppressive effect of miR-374b was determined by both in-vitro and in-vivo studies.Results: The expression of 380 miRNAs was evaluated in five human T-LBL tissues and correspondence normal peripheral blood T-cells by microRNA microarrays. The down-regulation of miR-374b was frequently detected in primary T-LBL tissues, which was significantly associated with patients worse overall survival (P<0.001) and increasing risk of recurrence (P=0.012). Functional assays demonstrated that miR-374b could suppress T-NHL cells proliferation in vitro and in vivo. Furthermore, miR-374b could also sensitize cells to both serum starvation- and chemotherapeutic agent-induced apoptosis. Significantly, subsequent investigation characterized two AKT pathway associated molecules, AKT1 and Wnt16, as direct targets of miR-374b and account for the effect of miR-374b in T-NHL cells. Consistently, in tissues of our T-LBL patients, AKT1 and Wnt16 expression was inversely correlated with miR-374b levels, and could also be independent predictors of recurrence and survival of these patients.Conclusions: Our data highlight the molecular etiology and clinical significance of miR-374b in T-LBL. Targeting miR-374b may represent a new therapeutic strategy to improve the therapy effect and survival for T-LBL patients. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Estrogen Receptor β Isoform 5 Confers Sensitivity of Breast Cancer Cell Lines to Chemotherapeutic Agent-Induced Apoptosis through Interaction with Bcl2L12

Alternative splicing of estrogen receptor β (ERβ) yields five isoforms, but their functions remain elusive. ERβ isoform5 (ERβ5) has been positively correlated with better prognosis and longer survival of patients with breast cancer (BCa) in various clinical studies. In this study, we investigated the inhibitory role of ERβ5 in BCa cells. Although ERβ5 does not reduce proliferation of BCa cell lines MCF-7 and MDA-MB-231, its ectopic expression significantly decreases their survival by sensitizing them to doxorubicin- or cisplatin-induced apoptosis through the intrinsic apoptotic pathway. Moreover, we discovered Bcl2L12, which belongs to the Bcl-2 family regulating apoptosis, to be a specific interacting partner of ERβ5, but not ERβ1 or ERα, in an estradiol-independent manner. Knockdown of Bcl2L12 enhanced doxorubicin- or cisplatin-induced apoptosis, and this process was further promoted by ectopic expression of ERβ5. Whereas Bcl2L12 was previously shown to inhibit apoptosis through binding to caspase 7, such interaction is reduced in the presence of ERβ5, suggesting a mechanism by which ERβ5 sensitizes cells to apoptosis. In conclusion, ERβ5 interacts with Bcl2L12 and functions in a novel estrogen-independent molecular pathway that promotes chemotherapeutic agent-induced in vitro apoptosis of BCa cell lines.

Phosphatidylinositol 3-kinases inhibitor LY294002 potentiates the cytotoxic effects of doxorubicin, vincristine, and etoposide in a panel of cancer cell lines

Many novel therapeutic approaches to overcome chemoresistance have involved targeting specific signaling pathways such as the phosphatidylinositol 3-kinase (PI3K) pathway. PI3K is a known stress response pathway which is involved in the regulation of cell survival, apoptosis, and growth. Inhibition of this pathway may possibly restore or augment the effectiveness of chemotherapy. Using three human malignant cell lines, we examined the effects of LY294002 (PI3K inhibitor) on chemotherapeutic agent-induced apoptosis and cytotoxicity. An antimicrotubule agent vincristine, a topoisomerase II inhibitor etoposide, and a DNA cross-linking agent doxorubicin were used accompanied with LY294002. Cell viability was determined by MTT assay, and the induction of apoptosis was assessed by immunoblotting of caspase-3. Blocking the PI3K/Akt cascade with a PI3K inhibitor LY294002 (10μM) increased the cytotoxic effect of vincristine and doxorubicin on SK-OV-3 cell line. Furthermore, LY294002 showed a greater promoting effect in etoposide- and doxorubicin-induced cytotoxicity on MDA-MB-468 and A549 cells. The quantity of cleaved caspase-3 in cancer cells that had combination therapy was increased compared with that in the cells treated with each drug alone. We suggest that inhibitors of the PI3K/Akt pathway in combination with chemotherapeutic agents may induce cell death effectively and be a potent modality to treat various types of cancer. The effectiveness of such combination therapy is depending to the used cell line and class of anticancer drug.

Overexpression of cyclin B1 antagonizes chemotherapeutic-induced apoptosis through PTEN/Akt pathway in human esophageal squamous cell carcinoma cells

The role of cyclin B1 in the clinical therapeutic sensitivity of human esophageal squamous cell carcinoma (ESCC) remains to be defined. In this study, we found that elevated cyclin B1 expression attenuated the apoptosis induced by cisplatin or paclitaxel, while knockdown of cyclin B1 enhanced cisplatin or paclitaxel sensitivity in ESCC cells. Cyclin B1-mediated apoptosis may rely on the Bcl-2-dependent mitochondria-regulated intrinsic death pathway, and the antagonizing effect of cyclin B1 on chemotherapeutic agent-induced apoptosis was through PTEN/Akt pathway. Therefore, cyclin B1 might be a therapeutic target for the development of specific and efficient approaches in the treatment of ESCC.

COX-2 inhibitors block chemotherapeutic agent-induced apoptosis prior to commitment in hematopoietic cancer cells

Enzymatic inhibitors of pro-inflammatory cyclooxygenase-2 (COX-2) possess multiple anti-cancer effects, including chemosensitization. These effects are not always linked to the inhibition of the COX-2 enzyme. Here we analyze the effects of three COX-2 enzyme inhibitors (nimesulide, NS-398 and celecoxib) on apoptosis in different hematopoietic cancer models. Surprisingly, COX-2 inhibitors strongly prevent apoptosis induced by a panel of chemotherapeutic agents. We selected U937 cells as a model of sensitive cells for further studies. Here, we provide evidence that the protective effect is COX-independent. No suppression of the low basal prostaglandin (PG)E 2 production may be observed upon treatment by COX-2 inhibitors. Besides, the non-active celecoxib analog 2,5-dimethyl-celecoxib is able to protect from apoptosis as well. We demonstrate early prevention of the stress-induced apoptotic signaling, prior to Bax/Bak activation. This preventive effect fits with an impairment of the ability of chemotherapeutic agents to trigger apoptogenic stress. Accordingly, etoposide-induced DNA damage is strongly attenuated in the presence of COX-2 inhibitors. In contrast, COX-2 inhibitors do not exert any anti-apoptotic activity when cells are challenged with physiological stimuli (anti-Fas, TNFα or Trail) or with hydrogen peroxide, which do not require internalization and/or are not targeted by chemoresistance proteins. Altogether, our findings show a differential off-target anti-apoptotic effect of COX-2 inhibitors on intrinsic vs. extrinsic apoptosis at the very early steps of intracellular signaling, prior to commitment. The results imply that an exacerbation of the chemoresistance phenomena may be implicated.

Abstract 4414: Clinical significance of CHD1L in hepatocellular carcinoma and therapeutic potentials of virus-mediated CHD1L depletion

Abstract Background: Hepatocellular carcinoma (HCC) is among the most lethal of human malignancies. It is difficult to detect early, has a high recurrence rate and is refractory to chemotherapies. Amplification of 1q21 is one of the most frequent genetic alterations in HCC. CHD1L is a newly identified oncogene responsible for 1q21 amplicon. This study aims to investigate the role of CHD1L in predicting prognosis and chemotherapy response of HCC patients, its chemo-resistant mechanism and whether virus-mediated CHD1L silencing has therapeutic potentials for HCC treatment. Methods: We assessed the clinical significance of CHD1L in a cohort of 109 HCC cases including 50 cases who received transarterial chemoembolization (TACE) treatment by clinical correlation and Kaplan-Meier analyses. CHD1L-overexpressing cell model was generated and the mechanism of CHD1L-involved chemo-resistance was investigated. Adenovirus-mediated silencing method was used to knockdown CHD1L and its effects on tumorigenicity as well as chemo-resistance were investigated in vivo and in vitro. Results: Overexpression of CHD1L was significantly associated with tumor microsatellite formation (p=0.045), advanced tumor stage (p=0.018), overall survival (OS) time (p=0.002), OS time of patients who received TACE treatment (p=0.028) and chemo-resistance (p=0.020) in HCC. Interestingly, CHD1L could inhibit apoptosis induced by 5-fluorourail (5-FU) but not doxorubicin (DOX). The mechanistic study revealed that the involvement of Nur77-mediated pathway in chemotherapeutic agent-induced apoptosis can dictate if CHD1L could confer resistance to chemotherapy. Furthermore, adenoviral vector containing shRNAs against CHD1L (CHD1L-shRNAs) could suppress cell growth, clonogenicity and chemo-resistance to 5-FU. In vivo study found that CHD1L-shRNAs could inhibit xenograft tumor growth and increase the sensitivity of tumor cells to 5-FU in nude mice. Conclusions: Our study highlighted for the first time the prognostic value of CHD1L in HCC and the potential application of virus-mediated CHD1L silencing in HCC therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4414. doi:10.1158/1538-7445.AM2011-4414

GROβ and its downstream effector EGR1 regulate cisplatin-induced apoptosis in WHCO1 cells

Cisplatin is one of the most widely used chemotherapeutic agents employed for treatment of a wide variety of solid tumors, including human esophageal squamous cell carcinoma (ESCC). However, a major limitation of cisplatin-based chemotherapy of ESCC is the rather low-effective rate. Understanding the molecular events of limited efficacy of cisplatin-based chemotherapy of ESCC could lead to strategies resulting in improved therapeutic benefits. The CXC chemokine family has been reported to be related to inflammatory reaction, injure recovery, cell proliferation, apoptosis and even to be involved in the regulation of chemotherapeutic agent-induced apoptosis. CXCL2 chemokine, also known as GROβ (growth-related gene product β), belongs to the CXC chemokine group. The known functions of GROβ are related to attracting neutrophils to sites of inflammation, modulation of the neurotransmitter release, cell proliferation and apoptosis. However, little is known about the relationship between GROβ and chemotherapeutic agent-induced apoptosis. This study was designed to provide insights into the possible role of GROβ in the regulation of cisplatin-induced apoptosis in ESCCs. We report here that inhibition of expression of GROβ can decrease cisplatin-induced apoptosis in WHCO1 cells. EGR1 is a downstream factor regulated by GROβ. Silencing expression of EGR1 can also decrease cisplatin-induced apoptosis in WHCO1 cells. The activation of caspase 9 was delayed in cells in which GROβ and EGR1 were knocked down after cisplatin treatment. All these results indicate that GROβ and its downstream factor EGR1 are involved in regulating cisplatin-induced apoptosis in WHCO1 cells, and during this process the intrinsic apoptotic pathway is activated. It may be useful to examine the expression levels of GROβ and EGR1 in ESCC patients to select those likely to respond well to cisplatin.

Clinical significance of CHD1L in hepatocellular carcinoma and therapeutic potentials of virus-mediated CHD1L depletion

BackgroundHepatocellular carcinoma (HCC) is among the most lethal of human malignancies. It is difficult to detect early, has a high recurrence rate and is refractory to chemotherapies. Amplification of 1q21...

Cytoplasmic FANCA-FANCC Complex Interacts and Stabilizes the Cytoplasm-dislocalized Leukemic Nucleophosmin Protein (NPMc)

Eight of the Fanconi anemia (FA) proteins form a core complex that activates the FA pathway. Some core complex components also form subcomplexes for yet-to-be-elucidated functions. Here, we have analyzed the interaction between a cytoplasmic FA subcomplex and the leukemic nucleophosmin (NPMc). Exogenous NPMc was degraded rapidly in FA acute myeloid leukemia bone marrow cells. Knockdown of FANCA or FANCC in leukemic OCI/AML3 cells induced rapid degradation of endogenous NPMc. NPMc degradation was mediated by the ubiquitin-proteasome pathway involving the IBR-type RING-finger E3 ubiquitin ligase IBRDC2, and genetic correction of FA-A or FA-C lymphoblasts prevented NPMc ubiquitination. Moreover, cytoplasmic FANCA and FANCC formed a cytoplasmic complex and interacted with NPMc. Using a patient-derived FANCC mutant and a nuclearized FANCC, we demonstrated that the cytoplasmic FANCA-FANCC complex was essential for NPMc stability. Finally, depletion of FANCA and FANCC in NPMc-positive leukemic cells significantly increased inflammation and chemoresistance through NF-κB activation. Our findings not only reveal the molecular mechanism involving cytoplasmic retention of NPMc but also suggest cytoplasmic function of FANCA and FANCC in NPMc-related leukemogenesis.

Abstract 2026: MicroRNA-214 is a negative regulator of p53

Abstract The p53 transcription factor mediates multiple cellular functions including the response to genotoxic stress, differentiation, cell cycle and apoptosis. Since p53 inactivation is a critical event in tumor development, the regulation of p53 and its pathway is of prime importance in the understanding of tumorigenesis. While a number of microRNAs have been shown to be regulated by p53, microRNA regulation of p53 is still not well documented. Here we demonstrate that miR-214, a putative oncogenic miRNA, regulates p53 protein but not mRNA level by direct targeting 3′UTR of p53. Ectopic expression of miR-214 represses p53 and enhances the resistance to radiation- or chemotherapeutic agent-induced cell cycle arrest and apoptosis in wild-type but not mutated p53 cells. Introduction of p53 cDNA lacking 3′UTR largely abrogates miR-214-induced cell growth and survival. Depletion of endogenous miR-214 elevates protein level of p53 and induces apoptosis in human cancer cell lines expressing wild-type p53. These findings indicate that miR-214 is an important posttranscriptional regulator of p53 and exerts its oncogenic activity through targeting p53. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2026.