2022, Vol. 26 ›› Issue (1): 76-83

Expression and regulation of keratin 6B in CD44+ bladder cancer stem cells

Liu Lu, Yang Yuming, Shang Aichen, Liu Cui, Sun Ce, Wang Jing   

Abstract: BACKGROUND: Bladder cancer stem cells could promote the recurrence and drug resistance of bladder cancer. Numerous studies have shown that keratin 6B (KRT6B) is involved in the production and progression of tumors, and is closely related to the prognosis of tumors.
OBJECTIVE: To observe the expression of keratin 6B in CD44+ bladder cancer stem cells and to show the influence of keratin 6B on proliferation, migration, and self-renewal of bladder cancer stem cells, and to further explore the effect of keratin 6B expression on the prognosis of bladder cancer patients.
METHODS: (1) CD44+ 5637 bladder cancer stem cells were isolated by magnetic active cell sorting. Cancer stem cell-related gene expression of SOX2, OCT4, and NANOG was detected via real-time polymerase chain reaction. The spheroid formation assay was used to detect the ability of self-renewal of cancer stem cells in CD44+ cells. Keratin 6B expression was detected in CD44+ bladder cancer stem cells by real-time polymerase chain reaction. (2) The CD44+ 5637 bladder cancer stem cells were divided into two groups. In the keratin 6B siRNA group, keratin 6B small interfering RNA was transfected into CD44+ bladder cancer stem cells. Untransfected CD44+ bladder cancer stem cells were used as the black control group. Cells were collected at 2 days post-transfection. The proliferation, migration, and self-renewal capacity of keratin 6B siRNA CD44+ bladder cancer stem cells were detected by the colony and wound healing assay and spheroid formation respectively. (3) Totally 24 bladder cancer tissues were used by immunohistochemistry to analyze the expression of CD44v6 and keratin 6B. (4) ONCOMINE database was used to analyze the effect of keratin 6B expression on the overall survival of bladder cancer.
RESULTS AND CONCLUSION: (1) Cancer stem cell-related genes (SOX2, OCT4, NANOG) and keratin 6B expression was higher in CD44+ cells isolated by magnetic active cell sorting compared with CD44- cells (P < 0.05). Cell proliferation, migration, and in vitro spheroid formation were significantly increased (P < 0.05). Keratin 6B small interfering RNA down-regulated the expression of keratin 6B in CD44+ bladder cancer stem cells (P < 0.05). (2) Compared with the blank control group, the proliferation and migration of CD44+ bladder cancer stem cells after transfection of keratin 6B small interfering RNA (P < 0.05), and the number of tumorsphere significantly diminished (P < 0.05); the expression of Notch1 and Hes1 mRNA increased (P < 0.05). (3) Keratin 6B and CD44v6 were significantly different in bladder cancer tissue (P=0.006). The overall survival rate of bladder cancer patients with high expression of keratin 6B was lower than that of patients with low expression of keratin 6B. (4) The results showed that keratin 6B was highly expressed in CD44+ bladder cancer stem cells, and could promote the proliferation, migration, and self-renewal capacity of bladder cancer stem cells. The high expression of keratin 6B contributes to improving the survival of bladder cancer patients.

Key words:stem cell, bladder cancer stem cell, keratin 6B, bladder cancer, siRNA, self-renewal, magnetic bead, spheroid formation assay