Relationship between telomerase activity and its subunit expression and inhibitory effect of antisense hTR on pancreatic carcinoma

Lactate Dehydrogenase B Is Required for Pancreatic Cancer Cell Immortalization Through Activation of Telomerase Activity

Telomerase activity is elevated in most cancer cells and is required for telomere length maintenance and immortalization of cancer cells. Glucose metabolic reprogramming is a hallmark of cancer and accompanied with increased expression of key metabolic enzymes. Whether these enzymes influence telomerase activity and cell immortalization remains unclear. In the current study, we screened metabolic enzymes using telomerase activity assay and identified lactate dehydrogenase B (LDHB) as a regulator of telomerase activity. Sodium lactate and sodium pyruvate did not influence telomerase activity, indicating LDHB regulates telomerase activity independent of its metabolism regulating function. Further studies revealed that LDHB directly interacted with TERT and regulated the interaction between TERT and TERC. Additionally, long-term knockdown of LDHB inhibited cancer cell growth and induced cell senescence in vitro and in vivo. Higher LDHB expression was detected in pancreatic cancer tissues compared with that in adjacent normal tissues and expression of LDHB correlated negatively with prognosis. Thus, we identified LDHB as the first glucose metabolic enzyme contributing to telomerase activity and pancreatic cancer cell immortalization.

T cell optimization for the treatment of pancreatic cancer

INTRODUCTION

Pancreatic cancer remains a deadly disease despite advances in surgery, chemotherapy, and radiation therapy. Treatment failure is likely due to intense chemoresistance and immunosuppression. Therefore, new treatment paradigms are urgently needed. Immunotherapy, particularly adoptive T cell transfer, is a highly-personalized therapy that involves the isolation and ex vivo expansion of tumor-specific T cells before administration to cancer-bearing hosts. Areas covered: This review summarizes different strategies of adoptive T cell therapy and their application in pancreatic cancer treatment. It also highlights recent advances and gives discussion on the future directions in T cell-based immunotherapy for pancreatic cancer. Expert opinion: Pancreatic ductal adenocarcinoma is extremely challenging to treat, in part, due to intense desmoplastic reaction and immunosuppression. The recent progress in cancer immunotherapy triggers a hope to use immunotherapeutic modality to treat pancreatic cancer. Immunotherapy is generally well tolerated, and has the potential to function as a monotherapy or in synergistic combination with conventional chemotherapy. We must make efforts to optimize the immunotherapeutic regimen and to select patients to treat based on their biological profile. To accomplish this goal, an intense collaboration is needed to bridge between bench and bedside.

Telomerase activity as a marker for differential diagnosis of pancreatic adenocarcinoma: a systematic review and meta-analysis

BACKGROUND

Studies evaluating the role of telomerase activity in pancreatic adenocarcinoma are inconsistent and a systemic review of the available literature may shed new light on this issue.

OBJECTIVE

To systematically review the usefulness of telomerase activity in distinguishing pancreatic cancer from other pancreatic diseases.

METHODS

A comprehensive search of the PubMed and Embase databases was conducted to identify eligible studies. Only studies evaluating telomerase activity in patients with suspected or previously diagnosed pancreatic adenocarcinomas versus nonpancreatic adenocarcinomas and published in English with a sufficient number of cases were included. The hierarchical summary receiver operating characteristic (HSROC) model was used to establish the potential value of telomerase activity in the diagnosis of pancreatic adenocarcinoma.

RESULTS

A total of 19 studies qualified for this meta-analysis. In distinguishing pancreatic adenocarcinoma from benign diseases, the pooled sensitivity and specificity of telomerase activity were 0.81 (95% CI, 0.68-0.90) and 0.97 (95% CI, 0.93-0.98), respectively; the diagnostic odds ratio (DOR) was 126.62 (95% CI, 49.94-320.99); beta was -1.16 (95% CI, -3.62-1.29), Z was -0.93, p was 0.35>0.1, and lambda was 6.86 (95% CI, 1.01-12.70). In distinguishing pancreatic adenocarcinoma from chronic pancreatitis, the pooled sensitivity and specificity of telomerase activity were 0.77 (95% CI, 0.61-0.88) and 0.97 (95% CI, 0.91-0.99), respectively; DOR was 117.28 (95% CI, 32.25-426.53); beta was -0.38 (95% CI, -1.89-1.13), Z was -0.49, p was 0.62>0.1, and lambda was 5.30 (95% CI, 3.37-7.24).

CONCLUSIONS

The present meta-analysis demonstrates that telomerase activity could be a useful biomarker for the differential diagnosis of pancreatic adenocarcinoma and benign pancreatic diseases.

Effect of imatinib on the signal transduction cascade regulating telomerase activity in K562 (BCR-ABL-positive) cells sensitive and resistant to imatinib

OBJECTIVE

Imatinib mesylate (IM) is a tyrosine kinase inhibitor selective for BCR-ABL and indicated for the treatment of chronic myeloid leukemia. It has recently been demonstrated that IM also targets other cellular components. Considering the significant role of telomerase in malignant transformation, we studied the effect of IM on telomerase activity (TA) and regulation in BCR-ABL-positive and -negative cells, sensitive and resistant to IM.

MATERIALS AND METHODS

Through combining telomeric repeat amplification protocol for detecting TA, reverse transcription polymerase chain reaction and Western blots for detecting RNA and protein levels of telomerase regulating proteins and fluorescence-activated cell sorting analysis, we showed that IM targets telomerase and the signal transduction cascade upstream of it.

RESULTS

IM significantly inhibited TA in BCR-ABL-positive and -negative cells and in chronic myeloid leukemia patients. TA inhibition was also observed in BCR-ABL positive cells resistant to IM at drug concentrations that did not lead to a reduction in BCR-ABL expression. In addition, a reduction in phosphorylated AKT and phosphorylated PDK-1 was also detected following IM incubation.

CONCLUSIONS

We demonstrate an inhibitory effect of IM on TA and on the AKT/PDK pathway. Because this effect was observed in cell expressing the BCR-ABL protein as well as cells not expressing it, and in cells sensitive as well as resistant to IM, it is reasonable to assume that the inhibitory effect of IM on TA is not mediated through known IM targets. The results of this study show that cells resistant to IM with regard to its effect on BCR-ABL could still be sensitive to IM treatment regarding other cellular components.

The expression of hTR and hTERT in human breast cancer: correlation with clinico-pathological parameters

BACKGROUND

Telomerase is a ribonucleoprotein enzyme that synthesizes telomeres after cell division and maintains chromosomal stability leading to cellular immortalization. Telomerase has been associated with negative prognostic indicators in some studies. The present study aims to detect any association between telomerase sub-units: hTERT and hTR and the prognostic indicators including tumour's size and grade, nodal status and patient's age.

METHODS

Tumour samples from 46 patients with primary invasive breast cancer and 3 patients with benign tumours were collected. RT-PCR analysis was used for the detection of hTR, hTERT, and PGM1 (as a housekeeping) genes expression.

RESULTS

The expression of hTR and hTERT was found in 31(67.4%) and 38 (82.6%) samples respectively. We observed a significant association between hTR gene expression and younger age at diagnosis (p = 0.019) when comparing patients < or = 40 years with those who are older than 40 years. None of the benign tumours expressed hTR gene. However, the expression of hTERT gene was revealed in 2 samples. No significant association between hTR and hTERT expression and tumour's grade, stage and nodal status was seen.

CONCLUSION

The expression of hTR and hTERT seems to be independent of tumour's stage. hTR expression probably plays a greater role in mammary tumourogenesis in younger women (< or = 40 years) and this may have therapeutic implications in the context of hTR targeting strategies.

Inhibitory effects of antisense phosphorothioate oligodeoxynucleotides on pancreatic cancer cell Bxpc-3 telomerase activity and cell growth in vitro

AIM: To investigate the effect of telomerase hTERT gene antisense oligonucleotide (hTERT-ASO) on proliferation and telomerase activity of pancreatic cancer cell line Bxpc-3.

METHODS: MTT assay was used to detect the effect of different doses of hTERT-ASO on proliferation of Bxpc-3 cell for different times. To study the anti-tumor activity, the cells were divided into there groups: Control group (pancreatic cancer cell Bxpc-3); antisense oligonucleotide (hTERT-ASO) group; and nosense oligonucleotide group decorated with phosphorothioate. Telomerase activity was detected using TRAP-PCR-ELISA. Cell DNA distribution was examined using flow cytometry assay. Cell apoptosis was observed by transmission electron microscope in each group.

RESULTS: After treatment with 6 mmol/L hTERT-ASO, cell proliferation was inhibited in dose- and time-dependent manner. The telomerase activity decreased after treatment with hTERT-ASO for 72 h. Flow cytometry showed the cell number of G₀/G₁ phase increased from 2.7% to 14.7%, the cell number of S phase decreased from 72.7% to 51.0%, and a sub-G1 stage cell apoptosis peak appeared in front of G1 stage.

CONCLUSION: Telomerase antisense oligodeoxy-nucleotide can inhibit the proliferation of pancreatic cancer cell line Bxpc-3 and decrease the telomerase activity and increase cell apoptosis rate in vitro.

Value of endoscopic methylene blue and Lugol's iodine double staining and detection of GST-Π and telomerase in the early diagnosis of esophageal carcinoma

AIM: To explore the expressions of GST-Π and telomerase activity in esophageal carcinoma and premalignant lesions and to investigate the value of endoscopic methylene blue (MB) and Lugol's iodine double staining.

METHODS: Seventy-two patients with esophagopathy were sprayed endoscopically with MB and Lugol's iodine in proper order and the areas stained blue and brown, and the area between the blue and brown stains were obtained. Depending on the pattern of mucosal staining, biopsy specimen was obtained. GST-Π and telomerase activity in specimens were examined by immunohis-tochemistry and PCR-based silver staining telomeric repeat amplification protocol, respectively.

RESULTS: After MB and Lugol's iodine staining, the area between both the colors was obtained in 64 of the 72 patients and the areas were stained blue and brown in all of the 72 patients. Association test of two simultaneous ordinal categorical data showed a correlation between the esophageal mucosal staining and the esophageal histology (P<0.005). The expression of GST-Π and telomerase activity in esophageal carcinoma and premalignant lesions increased. The expression of GST-Π and telomerase activity in dysplasia and carcinoma was significantly higher than that in normal epithelium (P<0.005). The expression in hyperplasia was slightly higher than that in normal epithelium. With the lesions progressing from low- to moderate- to high-grade dysplasia, the positive rate increased (P<0.025). Expression of GST-Π was correlated with that of telomerase activity in dysplasia and carcinoma (j = 0.4831, P<0.005; j = 0.3031, P<0.025, respectively); but there was no correlation between them in normal epithelium and hyperplasia.

CONCLUSION: The expression of GST-Π and telomerase may be an early event in the carcinogenesis of esophagus. They may play an induced and synergistic role with each other in the carcinogenesis of esophagus. Endoscopic MB and Lugol's iodine double staining and detection of GST-Π and telomerase activity may contribute to the early diagnosis of esophageal carcinoma.

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Aberrant expression and mutations of K-ras gene in pancreatic adenocarcinoma and chronic pancreatitis

AIM: To investigate frequency and clinical significance of P21^ras expression and K-ras mutations in pancreatic diseases and to identify their diagnostic values in pancreatic carcinoma.

METHODS: A total of 117 ductal lesions were identified in the available sections from pancreatic resection specimens of patients with pancreatic diseases, comprising 24 pancreatic ductal adenocarcinoma, 19 peritumoral ductal atypical hyperplasia, 58 peritumoral ductal hyperplasia and 19 normal duct at the tumor free resection margin. 24 ductal lesions were gotten from 24 chronic panctratitis. The expression of P21^ras was examined by immunohistochemical method. DNA was extracted. Codon 12 K-ras mutations were examined using the two-step polymerase chain reaction (PCR) combined with restriction enzyme digestion, followed by nonradioisotopic single-strand conformation polymorphism (SSCP) analysis by means of automated DNA sequencing.

RESULTS: The expression level of P21^ras in pancreatic carcinoma and chronic pancreatitis was higher than that of normal pancreatic tissue, but the expression of P21^ras in ductal hyperplasia neighboring pancreatic carcinoma was similar to that in ductal hyperplasia of chronic pancretitis. P21^ras showed a gradual stepwise increase in the frequency of expression ranged from normal pancreatic duct (0%), to hyperplasia duct (36.6%) and to atypical hyperplasia duct (78.9%). The expression level of P21^ras of atypical hyperplasia duct was higher than that of hyperplasia duct (P < 0.01). K-ras mutation rate of the pancreatic carcinoma was 79%, which was significantly higher than that in the chronic pancreatitis (33%) (P < 0.01). It was also found that K-ras mutation rate was gradually increased from normal duct at the tumor free resection margin, peritumoral ductal hyperplasia, peritumoral ductal atypical hyperplasia to pancreatic ductal adenocarcinoma. The mutation pattern of K-ras 12 codon of chronic pancreatitis was GGT→GAT, GGT and CGT, which was identical to that in pancreatic carcinoma.

CONCLUSION: Overexpression of P21^ras and K-ras mutation may play roles in the malignant transformation of pancreatic ductal cell. K-ras mutation only is not specific enough to diagnose pancreatic carcinoma.

Expression of MGMT, hMLH1 and hMSH2 and its clinopathological significance in pancreatic carcinoma tissues

AIM: To study the expression of MGMT, hMLH₁ and hMSH₂ and their clinicopathological significances in the tissues of chronic pancreatitis and pancreatic adenocarcinoma.

METHODS: The expression levels of MGMT, hMLH₁ and hMSH₂ were assayed by immunohistochemical method of avidin-biotin complex on the formalin-fixed and routinely paraffin-embedded sections of surgical resected specimen with chronic pancreatitis (n = 10) and pancreatic carcinoma (n = 51).

RESULTS: The positive rates and the scores of MGMT, hMLH₁ and hMSH₂ were significantly higher in chroinic pancreatitis than those of pancreatic carcinoma (MGMT: 100.0% vs 39.2%,3.8±0.8 vs 1.8±1.4; hMLH1: 100.0% vs 45.1%, 3.8±1.0 vs 1.7±1.6; hMSH2: 90.0% vs 50.9%, 3.5±0.9 vs 1.9±1.7). The positive rates and the scores of MGMT, hMLH₁ and hMSH₂ were significantly higher in well-differentiated adenocarcinomas than those of poorly differentiated adenocarcinomas (P < 0.05 or P < 0.01). The positive rates and the scores of MGMT, hMLH₁ and hMSH₂ were higher in metastasis-free cases than those of ones with metastasis, but no statistic difference was found (P>0.05). There was also no difference among the expression of three proteins and the other clinicopathological characteristics of pancreatic carcinoma.

CONCLUSION: The expression of MGMT, hMLH₁ or hMSH₂ may be related to the carcinogenesis and progression, and have inhibifory effects on the carcinogenesis and progression of pancreatic carcinoma.