Pan-Raf co-operates with PI3K-dependent signaling and critically contributes to myeloma cell survival independently of mutated RAS

The most common oncogenic mutations in multiple myeloma (MM) affect N- and K-RAS leading to constitutive activation of RAS-dependent signaling. Signal transduction via RAS, Raf and MAPK has been well described as a canonical pathway. In accordance with this assumption, we showed that the activity of the MEK/ERK module is strictly dependent on pan-Raf activity. However, inhibition of MEK/ERK has no or only minor effects on MM cell survival, whereas oncogenic Ras and pan-Raf critically contribute to survival of multiple myeloma cells. Therefore, we aimed to learn more about Raf-dependent but MEK-independent signaling effectors. We analyzed gene expression profiles in INA-6 cells after either pan-Raf inhibition with SB-590885 or MEK inhibition with PD-325901. Four biological replicates from each experimental group were analyzed with Affymetrix HGU133 Plus 2.0 microarrays.