HDAC9 and squamous cell carcinoma: Although Mcl-1 dominance renders squamous cell carcinoma cells resistant to ABT-737, the HDAC inhibitor vorinostat primes them for sensitivity to ABT-737 by shuttling Bim from Mcl-1 to Bcl-2/Bcl-xL, resulting in synergy for this drug combination and sustained tumor regression in vivo [579].