Heat Shock Protein Localisation in Chronic Lymphatic Leukaemia.

Heat Shock Proteins (Hsps) are a highly conserved group of molecular chaperones, the over-expression of which has been well documented in many cancer types. However, the location of these proteins within the cancer cell appears to be crucial in terms of tumour progression. Intracellular Hsp70 expression in particular appears to confer resistance to apoptosis, while surface Hsp70 expression has been shown to aid immune recognition of the cancer cell by NK cells. High intracellular levels of Hsp90 and Hsp27 also contribute to cell survival, while surface Hsp90 and Hsp27 have been shown to be required for tissue invasion and metastasis. However, the importance of these stress proteins in CLL progression is still poorly understood.

Using flow cytotmetry, we show that CLL patients express significantly higher levels of iHsp90 in lymphocytes (mean MFI CLL = 2463, Control = 748) and significantly higher levels of iHsp27 in lymphocytes (mean MFI CLL = 2138, Control = 760) than that expressed by age-matched control patients. The expression of iHsp90, but not Hsp27, in these patients was shown to be related to the stage of disease, and patients in Binet stage A appear to have a significantly higher expression than those in Binet stage C (p<0.001).

Hsp70 expression in CD5+/CD19+ cells, both intracellular and extracellular, showed either a very high level or a very low level of Hsp70 (see figure below). The high expressing groups were found also to be significantly different (p<0.01) from both the non-malignant cells from the same patients, and normal lymphocytes from age-matched controls. This was not the case for the low expressing groups. iHsp70 expression was also seen to be related to stage of disease as patients in Binet stages A and B were found to express significantly lower levels than those patients in Binet stage C.

Hsp expression was shown not to be associated with the apoptotic condition of the cell as analysis of active caspase-3 in CLL patients proved that the majority of the leukocytes were not apoptotic. Furthermore, the mean of fluorescence was significantly less in lymphocytes from CLL patients (mean MFI = 139) than those from control patients (mean MFI = 278).

Taken together these results show that Hsp expression changes with the natural progression of the disease and therefore manipulation of Hsps may be beneficial in the treatment of CLL.

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