Up-Regulation of LINC00665 Facilitates the Malignant Progression of Prostate Cancer by Epigenetically Silencing KLF2 Through EZH2 and LSD1

Abstract

This study aimed to explore the function of LINC00665 on the proliferation and metastasis of prostate cancer (PCa), and the potential regulatory mechanisms were also investigated. The expression level of LINC00665 in 50 pairs of PCa tissues and adjacent ones was studied by qRT-PCR, and the associations between LINC00665 and clinicopathological characteristics of PCa patients were analyzed. Control group (sh-NC) and LINC00665 knock-down group (sh-LINC00665) were set in 22RV1 and DU145 cells, respectively. The biological functions of LINC00665 in PCa cell lines were assessed by CCK-8, EdU, Transwell assays, and the nude mouse xenograft model was used to evaluate the tumorigenicity in vivo. In addition, qRT-PCR, Western Blot, RIP and ChIP assays were also used to determine the regulation mechanism of LINC00665 in PCa cell lines. In this study, our results showed that LINC00665 expression level in PCa cancer tissues was significantly up-regulated, compared with that in adjacent ones. Besides, similar results were found in PCa cell lines. Knock-down of LINC00665 significantly attenuated the proliferation and migration ability in 22RV1 and DU145 cells, compared to sh-NC. Mechanically, LINC00665 could interact with EZH2 and LSD1, recruiting them to KLF2 promoter region to inhibit its transcription. Moreover, the tumor-suppressive effects mediated by sh-LINC00665 were significantly reversed through the down-regulation of KLF2. Also, the suppression of LINC00665 impaired tumor growth of PCa in vivo. In summary, LINC00665 exerted the oncogenic functions in PCa cell lines by epigenetically silencing KLF2 expression by binding to EZH2 and LSD1, illuminating a novel mechanism of LINC00665 in the malignant progression of PCa and furnishing a prospective therapeutic biomarker to combat PCa.

The Emerging Roles of LINC00665 in Human Cancers

“… Xue et al (2021) found that LINC00665 was significantly upregulated in prostate cancer tissues and cell lines, and high expression of LINC00665 was correlated with the higher T stage and lymph node metastasis of prostate cancer patients. In addition, they performed the Kaplan-Meier survival analysis and found that the high LINC00665 expression level was associated with the poor survival of prostate cancer patients ( Xue et al, 2021 ). Furthermore, experiments have shown that LINC00665 knockdown inhibited the proliferation, migration, and invasion of prostate cancer cells ( Chen et al, 2020 ; Xue et al, 2021 ).…”

“…In addition, they performed the Kaplan-Meier survival analysis and found that the high LINC00665 expression level was associated with the poor survival of prostate cancer patients ( Xue et al, 2021 ). Furthermore, experiments have shown that LINC00665 knockdown inhibited the proliferation, migration, and invasion of prostate cancer cells ( Chen et al, 2020 ; Xue et al, 2021 ). In the process of exploring the mechanism, Chen et al (2020) found a negative correlation between miR-1224-5p and LINC00665 in prostate cancer.…”

“…Finally, they concluded that LINC00665 upregulated the expression of SND1 by inhibiting miR-1224-5p and ultimately promoted the progression of prostate cancer ( Chen et al, 2020 ). Xue et al (2021) conducted subcellular fractionation assays to confirm that LINC00665 was mainly located in the nucleus of prostate cancer cells, which indicated that LINC00665 might exert regulatory effects at transcriptional levels. Then, they confirmed that LINC00665 could directly bind with EZH2 and LSD1 in prostate cancer cells ( Xue et al, 2021 ).…”

“… Xue et al (2021) conducted subcellular fractionation assays to confirm that LINC00665 was mainly located in the nucleus of prostate cancer cells, which indicated that LINC00665 might exert regulatory effects at transcriptional levels. Then, they confirmed that LINC00665 could directly bind with EZH2 and LSD1 in prostate cancer cells ( Xue et al, 2021 ). They conducted ChIP analysis in prostate cancer cells and demonstrated that LINC00665 could recruit EZH2 and LSD1 to the KLF2 promoter region, leading to trimethylation of H3K27 or demethylation of H3K4 at this region ( Xue et al, 2021 ).…”

“…They conducted ChIP analysis in prostate cancer cells and demonstrated that LINC00665 could recruit EZH2 and LSD1 to the KLF2 promoter region, leading to trimethylation of H3K27 or demethylation of H3K4 at this region ( Xue et al, 2021 ). These results revealed that LINC00665 could inhibit the expression of KLF2 by interacting with EZH2 and LSD1 to promote prostate cancer progression ( Xue et al, 2021 ). In particular, one study showed that LINC0065 was steadily upregulated in prostate cancer cells 2 months after radiotherapy ( Eke et al, 2021 ).…”