Apoptotic markers for tumor recurrence: a minireview

The control of apoptotic mechanisms is integral to many aspects of tumor biology and appears to be involved in the process of recurrence. Apoptosis serves as an essential mechanism to prevent the proliferation of cells with a higher mutation rate, thus tempering malignant transformation. Most antineoplastic therapies function by triggering apoptosis in sensitive cells. Resistance to treatment may result from specific inhibition of apoptotic signaling. Chemotherapy or radiation may increase the mutation rate and hasten tumor evolution in cancer cells that are resistant to apoptosis. Summarizing the current evidence regarding the usefulness of various apoptotic markers for predicting tumor recurrence, the most extensively studied appear to be bcl-2 and p53, as well as the apoptotic rate itself, with promising prognostic potential in several neoplasias. Investigative results, however, mostly refer to multiple single-center retrospective studies, awaiting validation by large prospective clinical trials. Despite initial optimism, it becomes apparent that the measurement of one or more gene products is inadequate to directly predict a phenomenon as complex as the clinical outcome. One of the challenges that is only beginning to be addressed is the combined assessment of traditional prognostic parameters and molecular biomarkers by creating models or equations to predict the likelihood of recurrence. Such screening of patients may help define prognostic categories and influence treatment decisions.