Effects of combined siRNA-TR and -TERT on telomerase activity and growth of bladder transitional cell cancer BIU-87 cells

Regulation of telomerase towards tumor therapy

Cancer is an aging-related disease, while aging plays an important role in the development process of tumor, thus the two are inextricably associated. Telomere attrition is one of the recognized hallmark events of senescence. Hence, targeting telomerase which could extends telomere sequences to treat tumors is widely favored. Cancer cells rely on high activity of telomerase to maintain a strong proliferative potential. By inhibiting the expression or protein function of telomerase, the growth of cancer cells can be significantly suppressed. In addition, the human immune system itself has a defense system against malignant tumors. However, excessive cell division results in dramatic shortening on telomeres and decline in the function of immune organs that facilitates cancer cell evasion. It has been shown that increasing telomerase activity or telomere length of these immune cells can attenuate senescence, improve cellular viability, and enhance the immunosuppressive microenvironment of tumor. In this paper, we review the telomerase-targeting progress using different anti-tumor strategies from the perspectives of cancer cells and immune cells, respectively, as well as tracking the preclinical and clinical studies of some representative drugs for the prevention or treatment of tumors.

Long non-coding RNAs at work on telomeres: Functions and implications in cancer therapy

Long non-coding RNAs (lncRNAs) are known to regulate various biological processes including cancer. Cancer cells possess limitless replicative potential which is attained by telomere length maintenance while normal somatic cells have a limited lifespan because their telomeres shorten with every cell division ultimately triggering replicative senescence. Two lncRNAs have been observed to play a key role in telomere length maintenance. First is the lncRNA TERC (telomerase RNA component) which functions as a template for telomeric DNA synthesis in association with telomerase reverse transcriptase (TERT) which serves as the catalytic component. Together they constitute the telomerase complex which functions as a reverse transcriptase to elongate telomeres. Second lncRNA that helps in regulating telomere length is the telomeric repeat-containing RNA (TERRA) which is transcribed from the subtelomeric region and extends to the telomeric region. TERC and TERRA exhibit important functions in cancer with implications in precision oncology. In this review, we discuss various aspects of these important lncRNAs in humans and their role in cancer along with recent advancements in their anticancer therapeutic application.

Telomere Gene Therapy: Polarizing Therapeutic Goals for Treatment of Various Diseases

Modulation of telomerase maintenance by gene therapy must meet two polarizing requirements to achieve different therapeutic outcomes: Anti-aging/regenerative applications require upregulation, while anticancer applications necessitate suppression of various genes integral to telomere maintenance (e.g., telomerase, telomerase RNA components, and shelterin complex). Patients suffering from aging-associated illnesses often exhibit telomere attrition, which promotes chromosomal instability and cellular senescence, thus requiring the transfer of telomere maintenance-related genes to improve patient outcomes. However, reactivation and overexpression of telomerase are observed in 85% of cancer patients; this process is integral to cancer immortality. Thus, telomere-associated genes in the scope of cancer gene therapy must be inactivated or inhibited to induce anticancer effects. These contradicting requirements for achieving different therapeutic outcomes mean that any vector-mediated upregulation of telomere-associated genes must be accompanied by rigorous evaluation of potential oncogenesis. Thus, this review aims to discuss how telomere-associated genes are being targeted or utilized in various gene therapy applications and provides some insight into currently available safety hazard assessments.

Identification and Validation of Gene Expression Patterns in Cystitis Glandularis Patients and Controls

Our aim was to investigate differences in gene expression in bladder tissues between cystitis glandularis (CG) patients and healthy controls. Subsequent RNA was isolated from urinary bladder samples from CG patients and healthy controls, followed by RNA sequencing analysis. There were 4263 differentially expressed genes in urinary bladder between CG patients and controls, and 8 genes were verified with real-time PCR, Western blot, and enzyme-linked immunosorbent assay (ELISA) analysis. Gene set enrichment analysis (GSEA) revealed that 25 signaling pathways were upregulated in CG patients, and 17 signaling pathways were found upregulated in healthy controls. The mRNA expression levels of the indicated genes, including CCND1, CCNA1, EGFR, AR, CX3CL1, CXCL6, and CXCL1, were significantly increased in urinary bladder from CG and bladder cancer (BC) patients compared with healthy controls, while TP53 was decreased. CX3CL1, CXCL6, and CXCL1 concentrations in peripheral blood from CG and BC patients were significantly increased compared with healthy controls. The protein expression levels of CCND1, EGFR, and AR were significantly increased in urinary bladder from CG and BC patients compared with healthy controls. In conclusion, the gene expression profile of CG patients has established a foundation to study the gene mechanism of CG and BC progression.

Targeting Human Telomerase Reverse Transcriptase by a Simple siRNA Expression Cassette in HepG2 Cells

BACKGROUND

Human telomerase reverse transcriptase (hTERT) has become an ideal target for development of anticancer therapy. Small interfering RNAs (siRNAs) are very powerful reagents for gene silencing and show promise for cancer gene therapy. However, only a small number of siRNAs have been demonstrated to be effective. For gene therapy targeting hTERT, it is essential to develop a robust system to fully explore the power of siRNAs.

OBJECTIVES

We explored a siRNA expression cassette (SEC) to screen highly effective RNAi-targeted sequences for gene therapy of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

An SEC was developed by flanking H1 and U6 promoters in opposite directions at the siRNA-encoding sequence. Eight SECs specific to hTERT were designed by overlap extension polymerase chain reaction (PCR) and transfected into HepG2 cells with calcium phosphate. The telomerase activity was determined by telomeric repeat amplification protocol (TRAP) silver staining and TRAP real-time PCR analysis. The mRNA and protein expression levels of hTERT were determined by reverse transcription (RT)-PCR and western blot, respectively. Cell viability was determined by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and cell apoptosis was measured by the annexin-V/propidium iodide (PI) assay coupled with flow cytometry.

RESULTS

Eight hTERT-specific SECs (SEC-1-8) were successfully constructed. In comparison to that of the negative control SEC, the hTERT-specific SECs, especially, SEC-4, SEC-5, SEC-7 and SEC-8 significantly reduced the activity of hTERT in HepG2 cells at 48 hours after transfection. Moreover, the mRNA and protein expression levels of hTERT as well as the cell viability were significantly reduced by SECs. Knockdown of hTERT by SECs in HepG2 cells led to cell apoptosis.

CONCLUSIONS

Our developed simple SEC was a powerful strategy for screening highly effective RNAi-targeted sequences and showed promise for gene therapy of HCC.