Figure 1. Increased STAT3 activity in co-cultures is dependent on both cell:cell contact and secreted factor(s).

Confluent cultures of MCF-7 (2.5×10⁴/well) in a 24 well plate were incubated for 24 hours, then the cells were either left untreated or their conditioned media was collected and replaced with fresh media (without conditioned medium –c.m). Monocytes (2.5×10⁴ cells/well) were either added to tumor cell's cultures (both untreated and cells that received fresh media-c.m.) or were incubated alone or with tumor cell's conditioned medium (c.m). After 2 hours, nuclear extracts were prepared and tested for STAT3 activity using Non-Radioactive STAT3 Transcription Factor Assay. Comparable results were obtained in two independent experiments.