a, b. Cell viability (AlamarBlue assay, RFU: relative fluorescent unit) (a) and apoptosis (caspase3/7 activity, RLU: relative luminescence unit) (b) measured in NCI-H69 cells cultured with (red) or without (black) human astrocytes (hA), as in Extended Data Fig. 3c. c, d. As in (a-b) with NCI-H82 cells. e, f. As in (a-b) with SUBr1 cells. g, h. Relative cell viability (luciferase activity) of NCI-H69 (g) or NCI-H82 (h) cells co-cultured with (blue) or without (red) direct contact with hA during co-culture. i. Relative cell viability of NCI-H69 cells cultured in astrocyte-conditioned medium (hA Con-AM), SCLC-astrocyte co-culture-conditioned medium (hA + SCLC Con-AM), or SCLC-conditioned medium (SCLC Con-AM). n = 3 independent experiments. P values calculated by two-sided t-test for (b)(d)(f)(i) and two-way ANOVA for (a) (c)(e)(g)(h).