IL-6 in SCCSs induces Bcl-6. (A) Immunohistochemical analysis for Bcl-6 expression was performed on bone marrow (BM) tissue microarrays from healthy donors (NBM) and multiple myeloma (MM) patients. Representative results are shown. CD138 is stained in red; Bcl-6 is stained in brown. Control sample was stained without anti–Bcl-6 antibodies or anti-CD138. See supplemental Methods for image-acquisition information. (B) MM.1S and RPMI8226 cells were cultured with stromal cell–culture supernatants (SCCSs; S) or bone marrow stromal cells (BMSCs; Sc) for 12 hours. (C) MM.1S, interleukin-6 (IL-6)–starved INA6, RPMI8226, and U266 cells were cultured with SCCSs for 12 hours. (D) MM.1S, IL-6–starved INA6, RPMI8226, and U266 cells were cultured with IL-6 (5 ng/mL) for 12 hours. (E) MM.1S cells were cultured with IL-6 (5 ng/mL) for the indicated time periods. (F) MM.1S and IL-6–starved INA6 cells were cultured with IL-6 (1, 3, or 10 ng/mL) for 12 hours. (G) Patient MM cells were cultured with IL-6 (5 ng/mL) for 12 hours. (H) INA6 cells were cultured with IL-6 (5 ng/mL for 3 hours and 8 hours) or SCCSs for 8 hours. Total RNA was extracted, and Bcl-6 gene expression was examined by real-time RT-PCR () and normalized to expression of glyceraldehyde-3-phosphate dehydrogenase (□), which served as an internal control. *P < .01. (I) INA6 cells were cultured with or without IL-6 (5 ng/mL) for 12 hours. Cells were then washed and cultured for the indicated time periods. Whole-cell lysates were subjected to immunoblotting with indicated antibodies. Phospho-STAT3 served as positive control for IL-6–induced signal transduction.