SPT6 recruits SND1 to co-activate human telomerase reverse transcriptase to promote colon cancer progression.

Human telomerase reverse transcriptase (hTERT) plays an extremely important role in cancer initiation and development, including colorectal cancer (CRC). However, the precise upstream regulatory mechanisms of hTERT in different cancer types remain poorly understood. Here, we uncovered the candidate transcriptional factor of hTERT in CRC and explored its role and the corresponding molecular mechanisms in regulating hTERT expression and CRC survival with an aim of developing mechanism-based combinational targeting therapy. The possible binding proteins at the hTERT promoter were uncovered using pull-down/mass spectrometry analysis. The regulation of SPT6 on hTERT expression and CRC survival was evaluated in human CRC cell lines and mouse models. Mechanistic studies focusing on the synergy between SPT6 and staphylococcal nuclease and Tudor domain containing 1 (SND1) in controlling hTERT expression and CRC progression were conducted also in the above two levels. The expression correlation and clinical significance of SPT6, SND1, and hTERT were investigated in tumor tissues from murine models and patients with CRC in situ. SPT6 was identified as a possible transcriptional factor to bind to the hTERT promoter. SPT6 knockdown decreased the activity of hTERT promoter, downregulated the protein expression level of hTERT, suppressed proliferation, invasion, and stem-like properties, promoted apoptosis induction, and enhanced chemotherapeutic drug sensitivity in vitro. SPT6 silencing also led to the delay of tumor growth and metastasis in mice carrying xenografts of human-derived colon cancer cells. Mechanistically, SND1 interacted with SPT6 to co-control hTERT expression and CRC cell proliferation, stemness, and growth in vitro and in vivo. SPT6, SND1, and hTERT were highly expressed simultaneously in CRC tissues, both from the murine model and patients with CRC in situ, and pairwise expression among these three factors showed a significant positive correlation. In brief, our research demonstrated that SPT6 synergized with SND1 to promote CRC development by targeting hTERT and put forward that inhibiting the SPT6-SND1-hTERT axis may create a therapeutic vulnerability in CRC.

Targeting HMGB3/hTERT axis for radioresistance in cervical cancer.

BACKGROUND: Radiotherapy is regarded as a milestone for the cure of cervical cancer. However, clinical outcome heavily be hindered by radioresistance. So, exploring the underlying mechanism of radioresistance, and find potential target, well deserve fully emphasis. METHODS: In this study, we developed two novel radiation resistance cervical cancer cell lines, which could mimic clinical radioresistance. In order to find new potential targets, RNA-Seq, database analysis, streptavidin-agarose and LC/MS were used. Pull-down, luciferase and rescue assays were conducted to explore the regulatory mechanisms. To further evaluate the correlation between therapeutic responses and HMGB3/hTERT expression, 172 cervical cancer patients were recruited. RESULTS: Knockdown of HMGB3 significantly inhibit the DNA damage repair and induced more γH2AX foci, leading to enhanced chemo- and radio-sensitivity in vitro and in vivo, whereas HMGB3 overexpression has the opposite effects. HMGB3 promotes cell growth and radioresistance by transcriptionally up-regulating hTERT via the specifical binding of HMGB3 at the hTERT promoter region from - 902 to - 321. HMGB3 knockdown-mediated radiosensitization could be reversed by the overexpressed hTERT in both cervical cancer cell lines and xenograft tumor mouse model. Furthermore, clinical data from 172 cervical cancer patients proved that there was a positive correlation between HMGB3 and hTERT expression, and high expression of HMGB3/hTERT predicted poor response to radiotherapy, worse TNM stages and shorter survival time. CONCLUSION: Here, we have identified HMGB3/hTERT signaling axis as a new target for cervical cancer radioresistance. Our results provide new insights into the mechanism of cervical cancer radioresistance and indicate that targeting the HMGB3/hTERT signaling axis may benefit cervical cancer patients.

Poly(U) binding splicing factor 60 promotes renal cell carcinoma growth by transcriptionally upregulating telomerase reverse transcriptase.

Background: Abnormal transcriptional upregulation of telomerase reverse transcriptase (TERT) plays a dominant role in telomerase activation in various cancers. TERT promoter mutations (TPMs) have been identified as a key mechanism in TERT upregulation. However, the mechanism of TERT upregulation in cancers with low frequency of TPMs are not fully elucidated so far. Methods: The expression of PUF60 and TERT was detected by real-time PCR, western blot and immunohistochemistry. TERT promoter binding proteins were identified by streptavidin-agarose pulldown assay and mass spectrum (MS) analysis. The role of PUF60/TERT in renal cancer was evaluated on cell growth in vitro and in vivo. Results: In this study, we identify the regulation mechanism of TERT in renal cell carcinoma (RCC) cells which have rare TPMs but exert significant upregulation of TERT. We found that TERT was highly expressed in RCC tumor tissues, and elevated TERT expression was associated with poor prognosis for patients. We also detected the relatively rare TPM status in both RCC tumor tissues and RCC cell lines. Mechanistically, PUF60, a RNA binding protein, was identified as a novel TERT regulator which bound to the TERT and transcriptionally upregulated TERT expression in RCC cells. The in vitro and in vivo experiments also demonstrated that PUF60 could promote RCC cell growth through activation of TERT expression in a TPM status independent way. Furthermore, we showed that there was a strong correlation of the expression of PUF60 and TERT in RCC tumor tissues and RCC cell lines, and the patients with high expression of PUF60 and TERT had significantly shorter survival. Conclusions: Collectively, these results indicated that PUF60 transcriptionally upregulated TERT expression to promote RCC growth and progression in a TPM status independent way, suggesting that the PUF60/TERT signaling pathway may serve as potential prognostic biomarkers and therapeutic targets for RCC.