In recent years, the number of complex but clinically effective biologicals such as multi-specific antibody formats and fusion proteins has increased dramatically. However, compared to classical monoclonal antibodies (mAbs), these rather artificially designed therapeutic proteins have never undergone millions of years of evolution and thus often turn out to be difficult-to-express using mammalian expression systems such as Chinese hamster ovary (CHO) cells. To provide access to these sophisticated but effective drugs, host cell engineering of CHO production cell lines represents a promising approach to overcome low production yields. MicroRNAs (miRNAs) have recently gained much attention as next-generation cell engineering tools. However, only very little is known about the capability of miRNAs to specifically increase production of difficult-to-express proteins. In a previous study we identified miR-143 amongst others to improve protein production in CHO cells. Thus, the aim of the present study was to examine if miR-143 might be suitable to improve production of low yield protein candidates. Both transient and stable overexpression of miR-143 significantly improved protein production without negatively affecting cell growth and viability of different recombinant CHO cells. In addition, mitogen-activated protein kinase 7 (MAPK7) was identified as a putative target gene of miR-143-3p in CHO cells. Finally, siRNA-mediated knock-down of MAPK7 could be demonstrated to phenocopy pro-productive effects of miR-143. In summary, our data suggest that miR-143 might represent a novel genetic element to enhance production of difficult-to-express proteins in CHO cells which may be partly mediated by down-regulation of MAPK7. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1046-1058, 2017.