CD44 3'-Untranslated Region Functions as a Competing Endogenous RNA to Enhance NK Sensitivity of Liver Cancer Stem Cell by Regulating ULBP2 Expression

Abstract

Liver CSCs are a rare subpopulation of heterogenous liver cancer cells with self-renewal and differentiation properties, which has emerged as a promising therapeutic target. Compelling data shows that NK cells selectively eliminate human cancer derived CSCs like colorectal carcinoma, melanoma, and glioblastoma. But the effect of NK cells on liver CSCs still remains unknown. To study the cytotoxic effect of NK cells on liver CSCs and the mechanism, we performed cytotoxicity assay, ELISA assays, CRISPRi, qRT-PCR, immunoblotting, RNA immunoprecipitation, and luciferase reporter using two types of CSCs reprogrammed from HCC. CSCs derived from liver cancer were susceptible to NK cell mediated cytotoxicity. The susceptibility of liver CSCs to NK cell-mediated cytotoxicity declined significantly after silencing CD44 by CRISPRi-mediated gene knockdown. CD44 3ʹ UTR functioned as a ceRNA to regulate the expression of ULBP2 mainly by competing miR-34a. CD44 3ʹ UTR functioned as a ceRNA to enhance NK sensitivity of liver cancer stem cell by regulating ULBP2 expression.

CD44 as a tumor biomarker and therapeutic target

“…In hepatocellular carcinoma cells (HuH7) which originally express CD44s rather than CD44v, silence of CD44 gene impaired the potential of spheroid formation and enhanced sensitivity to sorafenib and 5-fluorouracil (5-FU), accompanied by remarkable downregulation of CSC-related genes including CD133 and EpCAM [19]. The 3′ untranslated region of CD44, acting as a competing endogenous RNA to microRNA-34a, boosts the sensitivity of liver CSCs to natural kill cells-mediated cytotoxicity via regulating UL16 binding protein 2 [26]. In addition, CD44 also exerts significant effects on caner invasion and metastasis of various tumor types [27], such as lung adenocarcinoma [18], breast cancer [28][29][30], neuroblastoma [31], gastric cancer [32], esophageal squamous cell carcinoma (ESCC) [33], colorectal cancer [34][35][36][37], prostate cancer [38], nasopharyngeal carcinoma [39], endometrial cancer [40], clear cell renal cell (RCC) carcinoma [41], pancreatic cancer [42], meningioma [43] and ovarian cancer [44].…”

Screening of immunosuppressive cells from colorectal adenocarcinoma and identification of prognostic markers

“…In this study, we finalized the relevant gene "KRT23 ULBP2 ASRGL1 SERPINA1 SCIN SLC28A2" that may affect Th-17 cells immune infiltration in COAD patients. We have now found that these genes are involved in the development of many diseases (42)(43)(44)(45)(46)(47)(48)(49),In non-gastrointestinal tumors, ASRGL1 has shown a high correlation in the prognosis of patients with locally advanced lymph node-negative prostate cancer and cervical cancer (42,50); SLC28A2 helps increase the role of ribavirin (RBV) in the treatment of viral hepatitis Hyperuricemia (HUA) has been implicated (48,51). KRT23 was identified as a specifically expressed gene in colorectal cancer and highly expressed in colorectal cancer (45).…”

<p>MicroRNA-6071 Suppresses Glioblastoma Progression Through the Inhibition of PI3K/AKT/mTOR Pathway by Binding to ULBP2</p>

“…25 In recent years, ULBP2, a ligand of NKG2D, is reported to be not expressed or at a low level in normal tissue cells and shows abnormal expression in cancer cells. 26,27 Previous studies have indicated that ULBP2 is highly expressed in liver cancer, 28 breast cancer, 24 cervical cancer 29 and melanoma. 25 In the present study, the analysis of the TCGA dataset indicated that the low expression of ULBP2 was significantly associated with a better prognosis in GBM patients.…”