Figure 7. HS-5 direct contact is sufficient to enhance survival of K562^S cells in the presence of imatinib, despite efficient β-catenin knockdown at 4 h and 8 h of co-culture.

a,b. K562^S cells were infected with either shSCR or shβcat and subject to culture in RM or HS-5 DC. A high dose of imatinib (5 μM) was used to push the system during short time points. At the indicated times, all cells were harvested and the GFP⁺ cells were isolated by FACS. Immunoblot analysis revealed that β-catenin stabilization takes at least 24 hours to occur and is not due to contamination by HS-5 stromal cells (a). Colony assays revealed that, despite efficient β-catenin knockdown at 4 h and 8 h of HS-5 co-culture, HS-5 DC still protected cells from the effects of short-term treatment with imatinib (b). Thus, while β-catenin protein is stabilized by HS-5 DC, it is not required for direct contact-mediated protection against TKI treatment. Bars represent SEM. *p<0.05.