Role of the microRNA-7 (miR-7) in the Inhibition of Chemoresistance and Migration of Lymphoma Non-Hodgkin's through Regulation of YY1 and KLF4

Since the discovery and description of microRNAs (miRs), these molecules have become very important, specifically due to their participation in the regulation of proteins and transcription factors involved in the development of cancer. The microRNA-7 (miR-7) has been described as a negative regulator of several proteins involved in cancer such as YY1 and KLF4 in various cancer subtypes. We have recently reported that YY1 and KLF4 play a role in Non-Hodgkin Lymphoma (NHL) and that the expression of KLF4 is regulated by YY1 (Valencia-Hipolito 2014, Morales-Martinez 2019). Therefore, in this study we analyzed the role of miR-7 in NHL through its effect on the negative regulation of YY1 and KLF4 in vitro, and also assessed its expression in clinical specimens from lymphoma patients. Expression of KLF4, YY1 and miR-7 was analyzed used real-time PCR in NHL-B cell lines (Ramos, Raji, DHL4 and 2F7). The expression of KLF4 and YY1 was inverse correlated with miR-7 expression, where Raji has higher miR-7 expression and DHL4 lower, and this correlated with inverse expression of YY1 and KLF4 in both cell lines, respectively. The possible regulation of YY1 and KLF4 by miR-7 was analyzed by using the inducible expression or inhibition of miR-7, (transfection with pre-miR-7 or mimetic miR-7 respectively) as well using reporter-system plasmids containing the 3 'UTR region of YY1 or KLF4. The role of miR-7 in NHL, through the negative regulation of YY1 and KLF4 was determined by chemoresistance/proliferation, and migration assays. The clinical implications of miR-7 in the negative regulation of YY1 and KLF4, were analyzed by ISH and IHC in a TMA with 43 samples of NHL subtypes: DLBCL and Follicular Lymphoma (FL). Our results showed an inverse correlation of miR-7 expression with KLF4 and YY1 expression in B-NHL cell lines, miR-7 is able to regulate the expression of YY1 and KLF4 by direct binding in the 3 'UTR region. Thus, the induced expression of miR-7 inhibited the constitutive expression of YY1 / KLF4, whereas the inhibition of miR-7 correlated with an increase in the expression of YY1 / KLF4. Likewise, the induced expression of miR-7 reverses the chemo resistance and inhibits the migration capacity of NHL-B cell lines. Also, all tumor tissues expressing miR-7 demonstrated a negative correlation with YY1 and KLF4 expression, which was more significant in the FL. Additionally the expression of miR-7 in FL was associated with clinical outcome. Our results show for the first time that miR-7 has a role in NHL through the negative regulation of YY1 and KLF4. These results confirm YY1 and KLF4 as possible therapeutic targets through the regulation of miR-7. References: -Valencia-Hipόlito A, et al Expression of KLF4 is a predictive marker for survival in pediatric Burkitt lymphoma. Leuk Lymphoma. 2014;55(8):1806-14 -Morales-Martinez M, Valencia-Hipolito A, Vega GG, Neri N, Nambo MJ, Alvarado I, Cuadra I, Duran-Padilla MA, Martinez-Maza O, Huerta-Yepez S, Vega MI. Regulation of Krüppel-Like Factor 4 (KLF4) expression through the transcription factor Yin-Yang 1 (YY1) in non-Hodgkin B-cell lymphoma. Oncotarget. 2019;10(22):2173-2188. No relevant conflicts of interest to declare.