Western blot using anti-SPS1 antibody shows detection of endogenous SPS1 in NIH3T3 cell. No signal is seen in lysates from cells after pre-treatment with SPS1 siRNA. Endogenous SPS1 can be detected in mouse kidney and liver tissue lysates. Negligible cross-reactivity is seen against recombinant SPS2. The primary antibody was used at a 1:1000 dilution. Personal Communication, D. Hatfield, NCI, Bethesda, MD.