Jan C. Liang

Chromosome Breaks and Sister Chromatid Exchange as Predictors of Second Cancers in Hodgkin's Disease

Hodgkins disease (HD) survivors face an increased risk of developing second cancers. We evaluated baseline cytogenetic biomarkers, sister chromatid exchange (SCE) and chromosome breaks [spontaneous (SCB) and bleomycin-induced (BIB)], as predictors of second cancer risk in a cohort of 105 adult HD patients. During follow-up, seven second cancers occurred. SCBs and BIBs showed no association with risk of second primaries. Multivariate Cox regression revealed that high levels of SCEs (relative risk (RR)=11.3, p=0.02) and age (RR=1.08, p=0.02) predicted second cancer risk. Histology, stage, and treatment were not associated with elevated risk. In conclusion, baseline SCE frequencies may be a useful biomarker for identifying HD patients at increased risk of developing second cancers. These results need to be verified in a larger cohort with a longer follow-up time.

Studies of BCR and ABL gene rearrangements in chronic myelogenous leukemia patients by conventional and pulsed-field gel electrophoresis using gel inserts

Continual monitoring of the presence of the Philadelphia (Ph) chromosome in patients with chronic myelogenous leukemia (CML) is important for diagnosis as well as evaluation of therapy response of these patients. Because the Ph chromosome has been characterized molecularly to involve a reciprocal translocation between the ABL and BCR genes, there is an increasing interest in the use of molecular probes to detect chromosomal rearrangements in this disease. While rearrangements involving the bcr region of the BCR gene can be detected by conventional gel electrophoresis (CGE), detection of those involving ABL generally requires pulsed-field gel electrophoresis (PFGE). Currently, however, CGE and PFGE require different methods of cell preparation, with isolated DNA used in CGE and gel inserts containing whole cells used in PFGE. In this study, we show that the gel-insert method of DNA preparation can be adapted for use in CGE with slight modification of the gel-running conditions. The advantages of this method are demonstrated by studying both bcr and ABL rearrangements in bone marrow and peripheral blood samples of CML patients. Furthermore, we report a novel finding that chromosomal breakpoints in the ABL gene of CML patients occur predominantly between exons 1b and 1a.

Mutagen sensitivity and cancer susceptibility. Report of a cancer‐prone family

A cancer‐prone family was studied to determine if certain chromosomal abnormalities might have pre‐disposed members to develop diverse types of malignancies. The types of neoplasia that occurred in this family included cancers of the breast and stomach, multiple myeloma, dermatofibrosarcoma, Wilms tumor, and leukemia; the latter three occurred in children at an early age. Peripheral lymphocytes from 13 family members were examined for the presence of constitutional chromosomal abnormalities, fragile sites, and mutagen sensitivity. Our data shows that all living members of this family who had cancers were hypersensitive to chromosome breakage induced by bleomycin. In contrast, neither constitutional chromosomal abnormality nor heritable type of folate‐sensitive fragile site was observed in any member. The above findings suggest that genetic defects affecting chromosomal breakage and repair may be contributing factors for cancer development in several members of this family.

A new chemotherapy regimen for treatment of Hodgkin's disease associated with minimal genotoxicity.

Recently, the combination chemotherapy Novantrone, Oncovin, Velban, Prednisone [NOVP] was developed by The University of Texas M. D. Anderson Cancer Center for treatment of Hodgkins disease [HD]. Preliminary clinical results show that NOVP is as effective as the traditional Mechlorethamine, Oncovin, Procarbazine, Prednisone [MOPP] regimen in achieving remission, but with fewer side-effects. To determine if NOVP is genotoxic, we studied the induction of chromosome breaks and sister chromatid exchanges [SCEs] in lymphocytes of 42 HD patients both before and during NOVP treatment. Furthermore, in vitro bleomycin treatment was used to unmask potential single-stranded DNA breaks inducted by the therapy. Our results showed that NOVP did not cause elevated levels of chromosome or single-stranded DNA breaks, or SCEs. These results together with previous findings that NOVP caused minimal acute and gonadal toxicities suggest that NOVP is less toxic than MOPP. Therefore, this new regimen shows promise as an effective and minimally toxic regimen for treatment of HD.