NFKB1 and neoplasm: Tumor-secreted solute factors are responsible for NF-κB activation in macrophages, since murine RAW264.7 macrophages stably expressing the NGL reporter responded with robust in vitro NF-κB activation to cell-free media conditioned by KrasMUT, but not by KrasWT or Kras-silenced, tumor cells (Figure 3A,B and Figure S9A,D,E).