Heat shock proteins (Hsps) are overexpressed in a wide range of human
cancers and are implicated in
tumor cell proliferation, differentiation, invasion,
metastasis, death, and recognition by the immune system. We review the current status of the role of Hsp expression in
cancer with special emphasis on the clinical setting. Although Hsp levels are not informative at the diagnostic level, they are useful
biomarkers for
carcinogenesis in some tissues and signal the degree of differentiation and the aggressiveness of some
cancers. In addition, the circulating levels of Hsp and anti-Hsp
antibodies in
cancer patients may be useful in
tumor diagnosis. Furthermore, several Hsp are implicated with the prognosis of specific
cancers, most notably Hsp27, whose expression is associated with poor prognosis in gastric, liver, and prostate
carcinoma, and
osteosarcomas, and Hsp70, which is correlated with poor prognosis in breast, endometrial, uterine cervical, and bladder
carcinomas. Increased Hsp expression may also predict the response to some anticancer treatments. For example, Hsp27 and Hsp70 are implicated in resistance to
chemotherapy in
breast cancer, Hsp27 predicts a poor response to
chemotherapy in
leukemia patients, whereas Hsp70 expression predicts a better response to
chemotherapy in
osteosarcomas. Implication of Hsp in
tumor progression and response to
therapy has led to its successful targeting in
therapy by 2 main strategies, including: (1) pharmacological modification of Hsp expression or
molecular chaperone activity and (2) use of Hsps in anticancer
vaccines, exploiting their ability to act as
immunological adjuvants. In conclusion, the present times are of importance for the field of Hsps in
cancer, with great contributions to both basic and clinical
cancer research.