CD44 and neoplasm: However, FSTL1+ tumor cells, which were most abundant in the PD-1+SMI group (Fig. 4C), expressed high levels of the lung CSCs marker genes CD44 and ALCAM (Additional file 1: Fig. S9D), and the CSCs score was significantly higher than those in the other subclusters, except for NEAT1+ and XIST+ tumor cells (Additional file 1: Fig. S9E).