Endoplasmic Reticulum Stress Induces HRD1 to Protect Alveolar Type II Epithelial Cells from Apoptosis Induced by Cigarette Smoke Extract.

BACKGROUND/AIMS: Cigarette smoking is a major risk factor of chronic obstructive pulmonary disease. This study aimed to examine the effects of cigarette smoke extract (CSE) on alveolar type II epithelial cells (AECII) and investigate the underlying mechanism. METHODS: Primary AECII were isolated from rat lung tissues and exposed to CSE. Apoptosis was detected by flow cytometry. Protein expression was detected by Western blot analysis. RESULTS: Primary rat AECII maintained morphological and physiological characteristic after 3 passages. CSE increased the expression of ER specific pro-apoptosis factors CHOP and caspase 12, and the phosphorylation of JNK in AECII. CSE activated ER stress signaling and increased the phosphorylation of PERK, eIF2α and IRE1. Furthermore, CSE induced the expression of Hrd1, a key factor of ER-associated degradation, in AECII. Knockdown of Hrd1 led to more than 2 fold increase of apoptosis, while overexpression of Hrd1 attenuated CSE induced apoptosis of AECII. CONCLUSIONS: Our results suggest that ER stress induces HRD1 to protect alveolar type II epithelial cells from apoptosis induced by CSE.

Promoter methylation-mediated downregulation of PRDM5 contributes to the development of lung squamous cell carcinoma.

PRDM5 has been proposed as a tumor suppressor frequently downregualted in tumor. In this study, lung squamous cell carcinoma tissues and adjacent nontumorous normal tissues were collected from 30 patients. PRDM5 expression was detected by reverse transcription polymerase chain reaction and Western blot analysis, DNA methylation of PRDM5 promoter was analyzed by methylation-specific PCR. SK-MES-1 cells or xenografts in nude mice were treated with 5-aza-2'-deoxycitydine, and cell proliferation and tumor growth in nude mice were examined. We found that PRDM5 promoter was methylated and PRDM5 expression at both mRNA and protein levels was reduced in lung squamous cell carcinoma tissues. Furthermore, PRDM5 promoter methylation was significantly correlated with tumor differentiation and lymph node metastasis of lung squamous cell carcinoma, but not with age, gender, smoking, or tumor grade. 5-aza-2'-deoxycitydine inhibited the proliferation of SK-MES-1 cells and the growth of xenografts in nude mice, accompanied by reduced methylation of PRDM5 promoter and increased expression of PRDM5. Taken together, our data suggest that PRDM5 is a tumor suppressor in lung cancer and is a promising target for the diagnosis, prognosis, and therapy of lung squamous cell carcinoma.

CHOP overexpression sensitizes human non-small cell lung cancer cells to cisplatin treatment by Bcl-2/JNK pathway.

C/EBP homologous protein (CHOP), a 29 kDa cellular protein, plays a role in regulating tumor proliferation, differentiation, metabolism, cell death, and in tumor resistance to chemotherapy. Non-small cell lung cancer (NSCLC) is a tumor of the respiratory system and drug resistance is prevalent among NSCLC clinical cell cultures. Herein, our study elucidated the effect of CHOP on NSCLC cells with cisplatin resistance and its mechanism. In a NSCLC cell line with cisplatin-resistance, CHOP expression was decreased, compared with A549 cells. Overexpression of CHOP decreased the cell viability and enhanced cell apoptosis in the cells treated with cisplatin. Expression of CHOP also inhibited the cell proliferation and metastasis. CHOP increased the therapeutic effect of cisplatin on NSCLC cells through the Bcl-2/JNK pathway. In summary, CHOP regulated cisplatin resistance in cells of NSCLC by promoting the expression of apoptotic proteins and inhibiting the Bcl-2/JNK signaling pathway, indicating the antitumor effects of CHOP.

Inactivation of 14-3-3 sigma by promoter methylation correlates with metastasis in nasopharyngeal carcinoma.

14-3-3 sigma, the downstream target of p53, is a negative regulator of cell cycle G2-M phase checkpoint in response to DNA damage. Our previous comparative proteomics study showed that 14-3-3 sigma was downregulated or lost in nasopharyngeal carcinoma (NPC) tissue compared with non-cancerous nasopharyngeal epithelial tissue (NNET). In this study, we further investigated for the epigenetic mechanism of 14-3-3 sigma inactivation. Methylation-specific PCR showed 14-3-3 sigma promoter methylation in 100% of analyzed NPC cell lines (4/4) but not in immortalized human nasopharyngeal epithelial cell line NP69. Treatment of the four NPC cell lines with the methyltransferase inhibitor 5-aza-2'-dC resulted in the demethylation and upregulation of 14-3-3 sigma. In tissues, 14-3-3 sigma promoter methylation occurred at a higher frequency in NPC, 63/75 (84%), compared to adjacent NNET, 7/25 (28%), and fully methylated 14-3-3 sigma promoter was detected in NPC but not in any of adjacent NNET. RT-PCR, Western blotting, and immunohistochemistry showed that 14-3-3 sigma expression was downregulated or lost in NPC with methylation, and there was a negative correlation between the expression levels and methylation statuses of 14-3-3 sigma gene. In addition, the patients with methylated 14-3-3 sigma presented a higher frequency of lymph node and distant metastasis, and an advanced clinical stage, and overexpression of 14-3-3 sigma in NPC cell line 5-8F with high metastatic potential was able to inhibit its in vitro invasive ability. Our data are the first to show that 14-3-3 sigma is frequently inactivated by promoter methylation in NPC and this aberrant methylation correlates with lymph node and distant metastasis.

The methylation profiles of PRDM promoters in non-small cell lung cancer.

BACKGROUND: Non-small cell lung cancer (NSCLC) is one of the leading malignant tumors worldwide. Aberrant gene promoter methylation contributes to NSCLC, and PRDM is a tumor suppressor gene family that possesses histone methyltransferase activity. This study aimed to investigate whether aberrant methylation of PRDM promoter is involved in NSCLC. MATERIALS AND METHODS: Primary tumor tissues, adjacent nontumorous tissues, and distant lung tissues were collected from 75 NSCLC patients including 52 lung squamous cell carcinoma (LSCC) patients and 23 lung adenocarcinoma patients. The expression of PRDMs was detected by polymerase chain reaction (PCR), Western blot, and immunohistochemical analysis. The methylation of PRDM promoters was detected by methylation-specific PCR. The correlation of methylation and expression of PRDMs with clinicopathological characteristics of patients were analyzed. RESULTS: mRNA expression of PRDM2, PRDM5, and PRDM16 was low or absent in tumor tissues compared to distant lung tissues. The methylation frequencies of PRDM2, PRDM5, and PRDM16 in tumor tissues were significantly higher than those in distal lung tissues. In LSCC patients, methylation of PRDM2 and PRDM16 was correlated with smoking status and methylation of PRDM5 was correlated with tumor differentiation. CONCLUSION: The expression of PRDM2, PRDM5, and PRDM16 is low or absent in NSCLC, and this is mainly due to gene promoter methylation. Smoking may be an important cause of PRDM2 and PRDM16 methylation in NSCLC.

[The relationship between the polymorphism of glutamate cysteine ligase modulatory subunit gene and the susceptibility to chronic obstructive pulmonary disease].

OBJECTIVE: To investigate whether glutamate cysteine ligase modulatory (GCLM) subunit gene polymorphism is associated with susceptibility to chronic obstructive pulmonary disease (COPD), and to study the relationship between polymorphism of GCLM gene with plasma gamma-glutamylcysteine synthetase (gamma-GCS) activity. METHODS: Blood samples of 104 stable phase COPD smokers (COPD group), 124 healthy smokers (C group) and 132 healthy never-smokers (H group) were collected, and then the genotypes of GCLM -588C/T and GCLM -23C/T polymorphism sites were detected by polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis (RFLP). The plasma gamma-GCS activity was measured by coupled enzyme procedure. RESULTS: (1) The distribution of -588CC, -588CT, -588TT genotypes were corresponding to -23GG, -23GT, -23TT respectively in all of the individuals. (2) The frequencies of -588CC genotype and -588 C allele were significantly lower in COPD group (62.3% and 79.2%) than in C group (84.7% and 91.9%) and H group (78.8% and 89.0%, P < 0.01). (3) In smokers, GCLM -588 T allele carried a higher risk to COPD, the odds ratio (OR value) to C allele was 3.0, and with a 95% confidence interval 1.7 - 5.3. (4) The plasma gamma-GCS activity was increased in C group [(282 +/- 58) U/mg.prot] and COPD group [(224 +/- 54) U/mg.prot] as compared with H group [(157 +/- 26) U/mg.prot, P < 0.01], and were higher in healthy smokers than in COPD smokers (P < 0.01). (5) The smokers with -588CC genotype had higher gamma-GCS activity than CT or TT genotype [(292 +/- 54), (225 +/- 45) U/mg.prot, P < 0.01 in C group and (245 +/- 52), (188 +/- 36) U/mg.prot, P < 0.01 in COPD group], but the difference did not exist in H group [(158 +/- 27), (153 +/- 25) U/mg.prot, P > 0.05]. CONCLUSION: The polymorphism of GCLM -588C/T and -23G/T sites were associated with susceptibility to COPD, and were associated with plasma gamma-GCS activity.

Bevacizumab induces A549 cell apoptosis through the mechanism of endoplasmic reticulum stress in vitro.

AIMS: To observe the effect of bevacizumab on human A549 cells and explore its mechanism. METHODS: After different concentrations (0 µM, 1 µM, 5 µM, 25 µM) of bevacizumab treating in A549 cells, CCK8 assay detect the impact of bevacizumab on A549 cell proliferation and flow cytometry determine the effect of bevacizumab on human A549 cells apoptosis. Real-time PCR and Western blotting detect the changing expression of the target gene (CHOP, caspase-4, IRE1, XBP-1) on mRNA and Protein level. RESULTS: Treatment with bevacizumab for 24-hr have induced cell death in a does-dependent manner dramatically (P<0.05). In terms of the mRNA level, expression of XBP-1 has increased obviously in each group (1 µM, 5 µM, 25 µM) (P<0.01); the expression of CHOP (25 µM) and caspase-4 (5 µM) have increased slightly (P<0.05). In terms of the protein level, the expression of CHOP has increased obviously in each group (1 µM, 5 µM, 25 µM) when compared with the control group (0 µM) (P<0.05). As for caspase-4 (5 µM, 25 µM), the expression have increased slightly when compared with the control group (0 µM) (P<0.05). CONCLUSION: Bevacizumab can induce A549 cell apoptosis through the mechanism of endoplasmic reticulum stress.

Methylation of PRDM2, PRDM5 and PRDM16 genes in lung cancer cells.

AIMS: To investigate the changes of expression and methylation status of PRDM2, PRDM5, PRDM16 in lung cancer cells after treatment with demethylation agent. METHODS: A549 (lung adenocarcinoma cell line), HTB-182 (lung squamous cell carcinoma cell line) and HBE (normal bronchial cell line) were treated with 5-aza-2dC. The methylation state of PRDM2, PRDM5, PRDM16 was detected by MSP. The expression of PRDM2, PRDM5, PRDM16 was detected by RT-PCR and Western blot analysis. Cell growth was detected by MTT assay. RESULTS: 5-aza-2-dC reduced the methylation of PRDM2, PRDM5, PRDM16 gene in A549 and HTB-182 cells but not in HBE cells. Consistently, 5-aza-2dC increased mRNA and protein expression of PRDM2, PRDM5, PRDM16 in A549 and HTB-182 cells but not in HBE cells. Furthermore, 5-aza-2dC inhibited the growth of A549 and HTB-182 cells but not HBE cells. CONCLUSIONS: PRDM2, PRDM5, PRDM16 promoters are methylated and their expression is suppressed in lung cancer cells. Demethylation drug 5-aza-2dC could upregulate the expression of PRDM2, PRDM5, PRDM16 and suppress lung cancer cell growth. 5-aza-2dC has potential to be used for lung cancer therapy by epigenetic mechanism.

[The effect of transcription factor KLF2 in expression of gamma-GCS depend on regulation by Nrf2 in lung of rats with chronic obstructive pulmonary disease].

OBJECTIVE: To study the expression of lung Krüppel-like transcription factor (KLF2/LKLF) in lung tissues of rats with chronic obstructive pulmonary disease (COPD) and the relationship between KLF2 and NF-E2-related factor 2 (Nrf2), and make further explore the effects of KLF2 on the expression of gamma-glutamylcysteine synthetase (gamma-GCS). METHODS: Twenty-two male SD rats were randomly divided into a COPD group (n = 10) and a normal control group (n = 11). The rat model of COPD established by cigarette smoking and intratracheal instillation of lipopolysaccharide (LPS), and lung tissues were obtained. The expressions of KLF2, Nrf2, gamma-GCS mRNA and protein in lung tissues were measured by immunohistochemistry (IHC), Western blot, in situ hybridization (ISH) and reverse transcription-polymerase chain reaction (RT-PCR). To explore the relationship between KLF2 and Nrf2 protein,we utilize the method of co-immunoprecipitation (CO-IP). RESULTS: IHC and Western blot showed that protein expressions of KLF2, Nrf2, gamma-GCS were higher in the lung tissues from rats with COPD than those in the control groups (all P < 0.05). The levels of KLF2, gamma-GCS mRNA were markedly increased in the COPD group (all P < 0.01) while Nrf2 mRNA expression in COPD group had no significant difference with that in control group ( P > 0.05). CO-IP result showed that KLF2 were obviously present in immunoprecipitates of Nrf2 (P < 0.01) . Linear correlation analysis showed that the level of KLF2 protein was positively correlated with the level of Nrf2 protein (P < 0.05), and KLF2, Nrf2 proteins were positively correlated with gamma-GCS mRNA and protein (all P < 0.05). CONCLUSION: The expression of KLF2 is significantly up-regulated in COPD, which maybe up-regulate gamma-GCS mRNA expression by increasing Nrf2 expression and nuclear translocation against oxidative stress.