Background Information

Glioblastoma is the most common and most aggressive malignant primary brain tumor. While occurring in only two to three cases per 100,000 people in North America, glioblastoma represents 52% of all functional tissue brain tumor cases and 20% of all intracranial tumors. Prognosis for those diagnosed with glioblastoma is poor, with a median survival time of about 14 months.¹

Patients with glioblastoma can be treated with alkylating agents, such as Temador® (temozolomide). Epigenetic silencing of the MGMT (O6-methylguanine-DNA methyltransferase) DNA-repair gene by promoter methylation compromises DNA repair and has been associated with longer survival in patients with glioblastoma who receive temozolomide.^2,3

Temozolomide kills tumor cells by producing cross-links between DNA strands and inhibiting DNA replication. The most common alkylation site is the O6 position of guanine. O6-methylguanine DNA methyltransferase (MGMT) is a DNA repair protein that reverses such DNA alkylation and confers chemoresistance by repairing DNA damage. Temozolomide seems to work by sensitizing the tumor cells to radiation.⁴

Recent clinical studies confirm that the presence of MGMT promoter methylation in tumor samples corresponds to an increased likelihood that tumor cells would be responsive to temozolomide.^3,4,5,6 If the promotor was methylated, temozolomide was more effective. It is estimated that approximately 40 to 50% of glioblastoma tumors exhibit MGMT gene methylation, which correlates significantly with reduced DNA damage repair induced by alkylating agents and significantly enhanced chemosensitivity.⁴

According to recent clinical trials, glioblastoma patients with MGMT methylation respond to temozolomide two to three times better than those lacking of MGMT methylation. Prolonged overall and progression-free survival at 24 months was 80% for those with MGMT methylation vs. 20% for those lacking MGMT methylation.

Diagnostic MGMT testing requires sufficient and optimally preserved tumor tissue. Cleveland Clinic’s MGMT methylation assay is a new, quantitative MSP test to detect the methylation status of brain tissue that has undergone thorough clinical evaluation. Our protocol calls for a minimal tissue sample size of ½-centimeter, which is much smaller than other laboratories that typically require at least a minimum 1-centimeter sample size. The best results are obtained with cryopreserved tumor specimens.

Background Information

A translocation between chromosomes 9 and 22, resulting in the formation of a BCR / ABL fusion transcript, has long been recognized as a hallmark of chronic myeloid leukemia (CML). Although the breakpoints in BCR and ABL are variable, in >95% of cases of CML, the translocation results in production of the p210 isoform of the fusion protein (e13a2 or e14a2 fusion genes).

Modern therapy for CML, including tyrosine kinase inhibitors, has resulted in effective therapeutic options for CML patients. With this advance in treatment has come the need for effective monitoring for the presence of minimal residual disease (MRD) and the ability to recognize disease progression at an early stage. Techniques such as fluorescence in situ
hybridization (FISH) and metaphase cytogenetics provide valuable information at the time of initial diagnosis of CML and metaphase cytogenetics is helpful for identifying the emergence of additional chromosomal abnormalities, however, neither of these techniques are sufficiently sensitive to monitor MRD.^[1],[2] For this reason, a BCR / ABL p210 quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) assay was developed, validated, and implemented in the Department of Molecular Pathology.

To facilitate comparison of quantitative RT-PCR results between laboratories and platforms, International Scale reference materials were established by the World Health Organization.^[3] Results of this assay are now reported on the International Scale.