Detection of the soluble heat shock protein 27 (hsp27) in human serum by an ELISA

Increased levels of autoantibodies against heat shock protein 27 (hsp27) in patients with breast, ovarian, or endometrial cancer strongly suggest the presence and increased levels of hsp27 in their circulation. Therefore, we have developed a sensitive and reproducible ELISA for quantification of soluble hsp27 levels in biological fluid such as serum. The assay is highly specific for hsp27. The limit of detection of the ELISA is about 0.5 ng/mL. The mean intra- and inter-coefficients of variation were 7.45 and 8.18, respectively. The recovery of the recombinant protein was nearly 100%. The assay could detect soluble hsp27 levels in normal human serum when the level was 0.5 ng/mL. Out of 28 serum samples we tested, 10 samples were not detected for any hsp27 level in our ELISA. However, hsp27 levels could be detected in the other 18 samples. The median serum hsp27 level was 3.27 ng/mL when all the 28 normal control samples were included. Low levels of hsp27 in normal human serum may be useful to distinguish the hsp27 levels in breast or other cancer patients during the progression of the disease. Therefore, the use of hsp27 ELISA could be extremely useful in evaluating the role of soluble hsp27 in breast or other cancers.