Gene therapy for sarcoma utilizing adenoviral transfer of the β-glucuronidase and bax genes and an anthracyline prodrug

Expression analysis of apoptosis-related markers TP53, BCL-2, BAX and c-MYC in female genital tract sarcomas

BACKGROUND

Most female genital tract sarcomas are highly malignant and fatal. Their aggressive growth pattern and poor response to chemotherapy are the major causes of death. Deregulation of the apoptosis pathway is related to tumorigenesis and chemodrug resistance. The purpose of this study was to investigate the expression status and relationship of the apoptosis-related markers TP53, BCL-2, BAX and c-MYC in this group of tumors. In addition, correlations of these markers with clinicopathologic findings and their prognostic significance were also examined.

METHODS

Paraffin blocks of female genital tract sarcoma tissue from 54 patients were obtained after pathology review. Protein expression of TP53, BCL-2, BAX and c-MYC was examined using immunohistochemical staining with standard procedures. A semiquantitative method was used to assess the staining result where scoring 1-3 was negative and 4-9 was positive for expression. The mutual relationships between TP53, BCL-2, BAX and c-MYC were examined. Associations between expression of the apoptotic markers and tumor stage as well as outcome were also analyzed.

RESULTS

We found that all 4 of the apoptosis-related markers were frequently expressed in female genital tract sarcomas. Of the 54 cases, 24 (44%) were positive for TP53, 23 (43%) for BCL-2, 25 (46%) for BAX, and 30 (56%) for c-MYC. A significant positive association was observed between BAX and c-MYC (p < 0.001). There was no significant difference for the expression status of the 4 markers in early and late stage tumors. In prognostic analysis, overexpression of TP53, late stage, and age were significant prognostic factors in both univariate and multivariate analyses.

CONCLUSION

Since changes in TP53, BCL-2, BAX and c-MYC frequently occur in female genital tract sarcomas, deregulation of apoptosis appears to be involved in the pathogenesis of this group of tumors. This mechanism may occur early in tumorigenesis and include the c-MYC/BAX apoptotic pathway or BCL-2. However, TP53 mutation may play a crucial role in this process, and clinically, it could be used as a prognostic indicator.

Suicide genes for cancer therapy

The principle of using suicide genes for gene directed enzyme prodrug therapy (GDEPT) of cancer has gained increasing significance during the 20 years since its inception. The astute application of suitable GDEPT systems should permit tumour ablation in the absence of off-target toxicity commonly associated with classical chemotherapy, a hypothesis which is supported by encouraging results in a multitude of pre-clinical animal models. This review provides a clear explanation of the rationale behind the GDEPT principle, outlining the advantages and limitations of different GDEPT strategies with respect to the roles of the bystander effect, the immune system and the selectivity of the activated prodrug in contributing to their therapeutic efficacy. An in-depth analysis of the most widely used suicide gene/prodrug combinations is presented, including details of the latest advances in enzyme and prodrug optimisation and results from the most recent clinical trials.