The effects of irradiation on the expression of a tumour rejection antigen (heat shock protein gp96) in human cervical cancer

Purpose: Studies were designed to analyse the effects of high doses of γ-irradiation on the expression of a tumour rejection antigen (heat shock protein gp96) in human cervical carcinoma cell lines. Materials and methods: The expression of heat shock protein gp96 was evaluated at the transcriptional (Northern blot) and posttranscriptional levels (Western blot) in two human cervical carcinoma cell lines following exposure to high doses of γ-irradiation. Results: Doses of γ-irradiation ranging from 25 to 100 Gy significantly and consistently increased the expression of heat shock protein gp96 on CaSki and HT-3 cervical cancer cells. The increase in the amount of protein was due to transcriptional up-regulation of this gene. Radiation doses unable to inhibit completely cell replication in the totality of tumour cells (i.e. 25 Gy), as well as higher (fully lethal) doses of irradiation (i.e. 50 to 100 Gy), were shown to up-regulate significantly the expression of heat shock protein gp96 mRNA in a dose-dependent manner. Conclusions: Recently, gp96 molecules have been implicated in the presentation of endogenous and viral antigens. A number of key elements in this pathway, including major histocompatibility complex (MHC) class I molecules as well as adhesion/costimulation molecules such as ICAM-1, are known to be sensitive to irradiation effects. The results show that radiation can also increase the expression of other immunologically important cell molecules such as a tumour rejection antigen (heat shock protein gp96) in human cervical cancer. Such findings may partially explain the increased immunogenicity of tumour cells following irradiation and further support a role for local radiation therapy as a powerful biologic response modifier.