MSLN and cancer: A clinical trial reported using mRNA CAR T cells that target mesothelin to treat cancer patients, and broad anti-tumor immune responses against different tumor antigens, other than CAR T-targeted antigen, were detected from two of the four reported patients, indicating multiple injections of RNA CAR T cells could result in epitope spreading, and the infused RNA CAR T cells not only served as tumor killers to directly lyse tumor cells but also served as an adjuvant/vaccine to boost immune responses against cancers (Beatty et al., 2014).