Sonal R. Bakshi

Spontaneous Chromosomal Instability in Breast Cancer Families

Spontaneous chromosomal instability has been correlated with cancer predisposition. In the present study, the phenomenon has been evaluated using two cytogenetic markers, namely, frequency of spontaneous sister chromatid exchanges (SCE) and spontaneous chromosomal aberrations (CA) in peripheral blood lymphocytes of hereditary breast cancer (HBC) patients (n = 11) and healthy blood relatives (HBR, n = 36). A statistically significant difference was observed for both the endpoints between HBC patients and controls (P < 0.001), HBC patients and HBR (P < 0.001), as well as HBR and controls (P < 0.001). Thus, 63.64% of the HBC patients and 25% of HBR showed a mean CA/cell value higher than the highest mean CA/cell value of the controls (0.11 CA/cell). Similarly, 81.81% of the HBC patients and 61.11% of HBR showed a mean SCE/cell value higher than the highest mean SCE/cell value of the controls (9.60 SCE/cell). Chromosomal aberrations were more frequently observed in the B and E group of chromosomes in HBC patients and HBR. These findings primarily indicate the high level of chromosomal instability in breast cancer families, and might be one of the predisposing factors for high risk of cancer in HBR.

Chromosome damaging effects of pan masala

Effects of aqueous extracts of a popular brand of pan masala with and without tobacco (PM-T and PM) were studied for short duration treatment employing an in vitro system. Metabolic activation with S9 mix was also included. Frequency of all the three cytogenetic endpoints viz., chromosome aberration (CA); sister chromatid exchange (SCE) and % micronucleated cells (% MNC) were found to be elevated significantly in a dose-dependent manner in cultures without metabolic activation. However, addition of S9 activation system resulted in suppression of chromosomal damage. Our findings indicate that pan masalas contain water soluble direct acting mutagens.

Pan masala — a genotoxic menace

Cytogenetic markers such as chromosome aberration (CA), sister-chromatid exchange (SCE) and micronucleated cells (MNC) were used to assess the genotoxic potential of dimethyl sulphoxide (DMSO) extract of pan masala with and without tobacco (PM-T and PM). Using in vitro short-term assays, the extracts were tested in the presence or absence of metabolic activation. In cultures without metabolic activation the extracts were found to increase the frequency of all the three parameters tested significantly, however those with activation elicited a weak response, implying that pan masalas contain solvent (DMSO)-soluble direct-acting mutagen.

Mitomycin C induced chromosomal aberrations in young cancer patients

Mitomycin-C (MMC) induced Chromosomal aberration (CA) frequencies were studied in 48 h peripheral blood lymphocyte (PBL) cultures of untreated cancer patients of young age (maximum age 12 years, n=77). Control population (n=71) consisted of age-matched group (maximum age 12 years, n=21); elder controls (minimum age 60 years, n=19) and healthy first degree relatives, i.e., parents or siblings of the pediatric cancer patients (mean age 24.3 years, n=31) as they share their genome and environment. Induced CA levels were found to be significantly higher among pediatric cancer patients as compared to control groups. The age-matched and elder control groups showed comparable CA levels. The first degree relatives controls showed higher induced CA levels as compared to pediatric and elder control groups. The present results indicate that there are different degrees of mutagen sensitivity prevailing in normal population. This may be responsible for differential cancer proneness. High degree of mutagen sensitivity in cancer patients may also be playing a major role in cancer onset at an early age.

Involvement of poly(ADP-ribose) polymerase in paraptotic cell death of D. discoideum

Paraptosis is mediated by several proteins, poly(ADP-ribose) polymerase being one of them. D. discoideum lacks caspases thus providing a better system to dissect out the role of PARP in paraptosis. The cell death phenotype in unicellular eukaryote, D. discoideum is similar to the programmed cell death phenotype of multicellular animals. However, the events downstream to the death signal of PCD in D. discoideum are yet to be understood. Our results emphasize that oxidative stress in D. discoideum lacking caspases leads to PARP activation, mitochondrial membrane potential changes, followed by the release of apoptosis inducing factor from mitochondria. AIF causes large scale DNA fragmentation, a hallmark feature of paraptosis. The role of PARP in paraptosis is reiterated via PARP inhibition by benzamide, PARG inhibition by gallotannin and PARP down-regulation, which delays paraptosis. PARP, PARG and AIF interplay is quintessential in paraptosis of D. discoideum. This is the first report to establish the involvement of PARP in the absence of caspase activity in D. discoideum which could be of evolutionary significance and gives a lead to understand the caspase independent paraptotic mechanism in higher organisms.

Trisomy 8 in leukemia: A GCRI experience.

Trisomy of chromosome 8 is frequently reported in myeloid lineage disorders and also detected in lymphoid neoplasms as well as solid tumors suggesting its role in neoplastic progression in general. It is likely to be a disease-modulating secondary event with underlying cryptic aberrations as it has been frequently reported in addition to known abnormalities contributing to clinical heterogeneity and modifying prognosis. Here, we share our findings of trisomy 8 in leukemia patients referred for diagnostic and prognostic cytogenetic assessment. Total 60 cases of trisomy 8, as a sole anomaly or in addition to other chromosomal aberrations, were reported (January 2005–September 2008). Unstimulated bone marrow or blood samples were cultured, followed by GTG banding and karyotyping as per the ISCN 2005. Patients with +8 were chronic myeloid leukemia (CML) (36), acute myeloid leukemia (AML) (17), and acute lymphoblastic leukemia (ALL) (7). In 7 patients, trisomy 8 was the sole anomaly, whereas in 6 patients +8 was in addition to normal clone, in 47 patients, the +8 was in addition to t(9;22), t(15;17), and others, including 3 with tetrasomy 8. Only one patient showed constitutional +8. The present study will form the basis of further cumulative studies to correlate potential differential effects of various karyotypic anomalies on disease progression and survival following a therapeutic regime. To unravel the role of extra 8 chromosome, constitutional chromosomal analysis and uniparental disomy will be considered.

Mutagen sensitivity in oral cancer patients, healthy tobacco chewers and controls.

OBJECTIVE To analyze chromosomal aberrations (CA) as an index of DNA damage, to measure DNA repair capability using mutagen sensitivity assay and to correlate tobacco exposure with CA. STUDY DESIGN Oral cancer patients, healthy tobacco chewers and healthy tobacco nonusers were studied for spontaneous and mutagen-induced CA. An arbitrary unit obtained for lifetime tobacco exposure (LTE) was compared with CA. RESULTS Mean levels of spontaneous and mitomycin-C-induced CA were higher in patients as compared to chewers and controls. DNA repair capability of patients was significantly deficient (p < or = 0.016) as compared to that of chewers. LTE was significantly higher (p = 0.004) in patients than chewers. Chewers having high LTE and spontaneous CA above cutoff levels might be at a greater risk of oral carcinogenesis. CONCLUSION There is a probable risk of oral carcinogenesis in healthy tobacco consumers having higher CA and LTE. Whether the deficient DNA repair capacity of oral cancer patients is due to the disease process or the tobacco exposure needs to be confirmed with a larger population study.

Phenotypic spectrum in uniparental disomy: Low incidence or lack of study?

CONTEXT: Alterations in the human chromosomal complement are expressed phenotypically ranging from (i) normal, via (ii) frequent fetal loss in otherwise normal person, to (iii) sub-clinical to severe mental retardation and dysmorphism in live births. A subtle and microscopically undetectable chromosomal alteration is uniparental disomy (UPD), which is known to be associated with distinct birth defects as per the chromosome involved and parental origin. UPD can be evident due to imprinted genes and/or activation of recessive mutations. AIMS: The present study comprises of data mining of published UPD cases with a focus on associated phenotypes. The goal was to identify non-random and recurrent associations between UPD and various genetic conditions, which can possibly indicate the presence of new imprinted genes. SETTINGS AND DESIGN: Data mining was carried out using the homepage “http://www.fish.uniklinikum-jena.de/UPD.html.”, an online catalog of published cases with UPD. MATERIALS AND METHODS: The UPD cases having normal karyotype and with or without clinical findings were selected to analyze the associated phenotypes for each chromosome, maternal or paternal involved in UPD. RESULTS: Our results revealed many genetic conditions (other than the known UPD syndromes) to be associated with UPD. Even in cases of bad obstetric history as well as normal individuals chance detection of UPD has been reported. CONCLUSIONS: The role of UPD in human genetic disorders needs to be studied by involving larger cohorts of individuals with birth defects as well as normal population. The genetic conditions were scrutinized in terms of inheritance patterns; majority of these were autosomal recessive indicating the role of UPD as an underlying mechanism.

Chromosomal Aberrations in Young Cancer Patients

Spontaneous level of chromosomal aberrations (CA) is considered to be indicative of inherent cancer predisposition, which plays a major role in total cancer incidence. We have studied spontaneous CA levels in in vitro cultured peripheral blood lymphocytes of pediatric cancer patients (n = 77). Results were compared with those of control subjects (n = 72), including: age-matched controls; elder controls (minimum age 60 years); and healthy first-degree relatives (FDR) of pediatric cancer patients. Pediatric cancer patients showed the highest mean CA/cell value, which was statistically significant as compared to their age-matched counterparts, elder controls, and the FDRs. As compared to 7% of all the three control groups collectively, 32.4% of pediatric cancer patients showed > 0.1 mean CA/cell value. One of the FDRs with a very high frequency of CA developed cancer within three years. The results suggest that spontaneous levels of chromosomal aberrations may be used as one of the biomarkers for cancer predisposition study.

A new recurring chromosome 13 abnormality in two older patients with de novo acute myeloid leukemia: An Indian experience

We report here two cases of trisomy 13 in acute myeloid leukemia M1 subtype. short-term unstimulated bone marrow and peripheral blood lymphocyte culture showed 47, XY, +13 in all metaphase plates and trisomy 13 was confirmed with whole chromosome paint probes. Trisomy 13 in AML-M1 is a rare numerical abnormality. This is the first Indian report of sole trisomy 13 in AML-M1. Here, we present two cases of elder male patients, which may constitute a distinct subtype.