Background <p>Aggressive tumors such as glioblastoma, breast, ovarian and pancreatic cancer have low survival rates and new therapies are urgently needed. One potential target is CD44v6, a splice variant of CD44 that is associated with poor prognosis. Recently, NK cells expressing CAR molecules have shown promise in combining specific targeting of solid tumors with a low risk of side effects. The aim of the current study is to explore the efficacy of the CD44v6-CAR construct expressed in the NK cell line NK92 against solid tumors both in vitro and in vivo.</p> Methods <p>Flow cytometry was used to evaluate the expression of CD44v6 on glioblastoma, breast, ovarian and pancreatic cancer cell lines. In order to investigate the efficacy of CD44v6-CAR-NK92 against these solid tumors in 2D and 3D models, cytotoxicity was measured using a luminescent cell viability assay. Additionally, we assessed the levels of IFN-γ in cell culture supernatants using an ELISA method. Finally, we evaluated our therapeutic in vivo using a xenografted murine model of ovarian cancer through bioluminescent imaging.</p> Results <p>CD44v6-CAR-NK92 cells exhibit specific cytotoxicity against glioblastoma, breast, ovarian and pancreatic cancer after 24&#xa0;h compared to the control, both in 2D and 3D models. Furthermore, the activity of CD44v6-CAR-NK92 was validated by quantifying specific cytokine release in response to target cells. Finally, we could show that CD44v6-CAR-NK92 was effective in reducing tumor burden in a xenografted murine model of ovarian cancer.</p> Conclusion <p>Our results demonstrate that CD44v6-CAR-NK92 cells could be an attractive therapeutic agent for the treatment of solid tumors.</p>