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Y A Luqmani

Publications and source records attributed to Y A Luqmani.

At least 19 recordsLinked to original sources
PubMed2005

Mechanisms of drug resistance in cancer chemotherapy.

The management of cancer involves procedures, which include surgery, radiotherapy and chemotherapy. Development of chemoresistance is a persistent problem during the treatment of local and disseminated disease. A plethora of cytotoxic drugs that selectively, but not exclusively, target actively proliferating cells include such diverse groups as DNA alkylating agents, antimetabolites, intercalating agents and mitotic inhibitors. Resistance constitutes a lack of response to drug-induced tumour growth inhibition; it may be inherent in a subpopulation of heterogeneous cancer cells or be acquired as a cellular response to drug exposure. Resistance varies. Although regulatory approval may require efficacy in as few as 20% of trial cohorts, a drug may subsequently be used in unselected patients displaying resistance to the treatment. Principal mechanisms may include altered membrane transport involving the P-glycoprotein product of the multidrug resistance (MDR) gene as well as other associated proteins, altered target enzyme (e.g. mutated topoisomerase II), decreased drug activation, increased drug degradation due to altered expression of drug-metabolising enzymes, drug inactivation due to conjugation with increased glutathione, subcellular redistribution, drug interaction, enhanced DNA repair and failure to apoptose as a result of mutated cell cycle proteins such as p53. Attempts to overcome resistance mainly involve the use of combination drug therapy using different classes of drugs with minimally overlapping toxicities to allow maximal dosages and with narrowest cycle intervals, necessary for bone marrow recovery. Adjuvant therapy with P-glycoprotein inhibitors and, in specific instances, the use of growth factor and protein kinase C inhibitors are newer experimental approaches that may also prove effective in abrogating or delaying onset of resistance. Gene knockout using antisense molecules may be another effective way of blocking drug resistance genes. Conversely, drug resistance may also be used to good purpose by transplanting retrovirally transformed CD34 cells expressing the MDR gene to protect the bone marrow during high-dose chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

Allelic variation of BAT-25 and BAT-26 mononucleotide repeat loci in tumours from a group of young women with breast cancer.

Genomic instability in the form of repeat number variation at microsatellite loci has been reported in several human cancers. To resolve current confusion regarding frequency of microsatellite instability (MSI), standardised protocols have proposed use of a consensus set of informative loci; it is claimed that analysis of 2 apparently quasi-homozygous, quasi-monomorphic, mononucleotide repeats (BAT-25 and BAT-26) is sufficiently accurate to define MSI (obviating need for corresponding constitutive DNA). We examined these loci in 163 breast cancers, 108 of which had previously been analysed at 11-24 other loci and found to have MSI in 38% of them. For BAT-26 only 1/153 (homozygous) tumours showed a contracted allele, with minor size variations (1-6 bp) between individuals. For BAT-25 repeat contractions were unambiguously observed in 12 (7.4%) tumours; only 4 of these were previously designated MSI+. DNA from normal individuals showed significant allelic variation in 8/159 (5%) cases for BAT-25; no instance of heterozygosity was seen for BAT-26. Subsequently, we analysed normal DNA from the 12 individuals whose tumours had MSI at BAT-25; in 2 cases there was germline heterozygosity. We conclude that analysis with BAT-26 (in contrast to other loci) was not a useful detector of MSI. With BAT-25, a low frequency of MSI not much greater than germline polymorphism, also limits the utility of this marker for determining MSI in breast cancer.

Alleles↗
PubMed2003

Frequent microsatellite alterations in a predominantly younger age of onset breast cancer population.

Microsatellite instability (MSI) and loss of heterozygosity (LOH) was investigated in paired tumour and normal tissue DNA from 108 predominantly premenopausal breast cancer patients (under age 45 years at presentation) for 25 simple repeat loci interspersed across 11 chromosomes. MSI was observed at a single locus in 69 (64%) patients; 41 of these had instability at more than one site. Greatest frequency of MSI was at loci D2S1356 (33%), D2S2739 (22%), D3S1766 (21%) and D13S796 (20%). LOH was seen at a single site in 55% of patients and at two or more sites in 27 patients with greatest frequency at D2S1356 (33%), D2S443 (19%) and D17S1299 (18%). Both mutations were found in the same patient but at different loci. Clearly, choice of loci is a determining factor in assessing genomic instability. The relatively high frequency of MSI may also reflect peculiarities of this younger patient population. Occurrence of MSI or LOH was unrelated to clinical stage, nodal status, tumour size or grade or steroid receptor status. It was independent of mutations detected in exons 5-9 of the p53 gene. There was no significant association with survival. The lack of such correlations reflects a random disabling mechanism that may equally affect genes promoting cell death as well as growth.

Adult↗
PubMed2001

Evaluation of prognostic factors in male breast cancer.

We conducted an analysis on 41 cases of male breast cancer (median age 54 y; range 25-82 y) in Kuwait. Most (51%) were stage II cancers with 65% arising in the left breast. There were 5 (12%) T1 tumours, 23 (56%) T2 tumours and 13 (32%) T3/T4 tumours. They were mostly (95%) infiltrating ductal carcinomas; 97% were grade 2 or 3. Axillary lymph node involvement was found in 69%. Estimated 5-year survival rates were 67% and 58% for overall and relapse free survival respectively. Favourable prognosis was associated with age below 50y, clinical stage I and II, small tumour size (T1, T2), low tumour grade and absence of nodal involvement or distant metastases; nodal status and grade were independent factors for relapse free survival in multivariate analysis. In 18 cases, an immunohistochemical study showed some degree of tumour antigen reaction for ER in 89% of cases, PR in 61%, pS2 in 44%, CathD in 72%, p53 in 56%, c-erbB-2 in 50%, Ki67 and PCNA in 100% and bcl-2 in 78%. There were significant associations between several of these factors but none influenced survival. Despite the high incidence of staining of ER, our data do not support the concept of an endocrine pathway that could be usefully antagonized with antioestrogens for therapeutic benefit, as in women.

Journal Article↗
PubMed2001

Multifocal squamous cell carcinoma of the oesophagus following radiotherapy for bilateral breast carcinoma.

A 60 year old woman who presented with dysphagia and weight loss was found to have multiple foci of dysplasia and in situ and invasive squamous cell carcinoma scattered along the whole length of the oesophagus, with intervening areas of normal mucosa. The patient had a history of two breast carcinomas 19 and one year previously for which she had repeated radiotherapy. Several members of the patient's close family had histories of malignant disease. All oesophageal lesions and the more recent breast cancer showed positive immunostaining for p53 protein. p53 mutations, some involving different exons, were also detected in these lesions. No p53 immunostaining or mutations were detected in the normal oesophageal mucosa. The findings suggest an independent origin of the multiple dysplastic and neoplastic foci, which might have developed in a background of a field change, possibly related to the previous radiotherapy. The strong family history of malignant diseases raises the possibility that, in addition, genetic factors might have played a role in the development of the oesophageal disease.

Breast Neoplasms↗
PubMed1998

CD5 positive breast carcinoma in a patient with untreated chronic lymphocytic leukaemia: molecular studies of chromosome 13q.

A 67 year old woman presented with a right breast lump which proved to be a grade 2 invasive ductal carcinoma with axillary lymph node metastasis. She had a five year history of CD5 positive chronic lymphocytic leukaemia, which never required treatment. Immunoperoxidase stains for CD5, using the monoclonal antibody NCL-CD-54C7, showed that there was extensive infiltration of axillary lymph nodes with CD5 positive B lymphocytes. Strong staining for CD5 was also seen in the carcinoma cells within the breast and lymph node metastases. It has recently been suggested that there is a tumour suppresser locus in chronic lymphocytic leukaemia at 13q12.3 near or at the BRCA2 locus. Deletion of regions on chromosome 13q containing the BRCA2 and RB1 genes has also been reported in sporadic breast cancers. These observations suggest that there may be a link between these two diseases acting through chromosome 13, but amplification of several microsatellite repeat markers failed to show any loss of heterozygosity or repeat instability at either these or several other loci on chromosome 13. Examination of additional such cases is needed to perform a more comprehensive study of the significance of positive CD5 staining of breast carcinoma.

Aged↗
PubMed1997

Steroid receptor measurement in breast cancers: comparison between ligand binding and enzyme-immunoassay in cytosolic and nuclear extracts.

We have analysed cytoplasmic and nuclear extracts of breast-cancer tissue from a total of 799 patients, measuring both oestrogen and progesterone receptors (ER, PR) using either the ligand binding assay (LBA) or the enzyme immunoassay technique (EIA). Mean and median receptor levels were much lower than those widely reported by others. For ER, this may in part be a consequence of the younger median age of the patient group. The frequency of positivity, using consensus cut-off values for clinical evaluation, was also lower than that reported by the EORTC Receptor Study Group. Although the measurements comparing the 2 methods were statistically correlated in terms of positivity, based on the above criteria for clinical assessment, concordance was considered to be relatively poor, particularly for ER when assayed in the same samples by the 2 methods. In cytosolic but not nuclear extracts, the LBA method gave a higher median value for ER than the EIA (except in the group that had EIA values greater than 15 fmol/mg protein); for PR, median values were higher with EIA in both cell fractions. There was an excellent correlation between receptor amounts in cytosolic and nuclear extracts for both ER and PR using the EIA; this was significantly better than with LBA. We also observed a correlation between ER and PR in both cytosolic and nuclear fractions which was most pronounced when the analysis was done by EIA. The amounts of ER in the cytosolic fraction were also correlated with the those of PR in the nuclear fraction and ER in the nuclear fraction with PR in the cytosolic fraction, but only when the EIA method was used. We conclude that the EIA method appears to be more sensitive and gives biologically more reliable results. However, the disagreement between the methods may be due to legitimate recognition of altered forms of the receptor and may be of biological significance. Although the presence of receptor in the cytosolic fraction is artifactual, its measurement by EIA does parallel the amounts of nuclear receptor, which may be a more relevant biological parameter.

Adult↗
PubMed1997

Presence of exon 5-deleted oestrogen receptor in human breast cancer: functional analysis and clinical significance.

A variant form of the human oestrogen receptor (ER) mRNA lacking sequences encoded within exon 5 has been described (Fuqua SAW, Fitzgerald SD, Chamness GC, Tandon AK, McDonnell DP, Nawaz Z, O'Malloy BW, McGuire WL 1991, Cancer Res 51: 105-109). We have examined the expression of the exon 5-deleted ER (HE delta5) mRNA variant in breast biopsies using reverse transcriptase polymerase chain reaction (RT - PCR). HE delta5 mRNA was present in only 13% of non-malignant breast tissues compared with 32% of carcinomas (95% CI, P=0.05). Presence of the HE delta5 mRNA was associated with the presence of immunohistochemically detected ER (P=0.015) and progesterone receptor (PR) (P=0.02). There was a positive correlation between the presence of HE delta5 and disease-free survival (P=0.05), suggesting that the presence of HE delta5 may be an indicator of better prognosis. We have raised a monoclonal antibody specific to the C-terminal amino acids of HE delta5. This antibody recognized the variant but not the wild-type ER protein. We show that HE delta5 protein is present in breast cancer using immunohistochemical techniques. We also analysed trans-activation by HE delta5 in mammalian cells and showed that, in MCF-7 cells, HE delta5 competes with wild-type ER to inhibit ERE-dependent trans-activation. Our results indicate that this variant is unlikely to be responsible for endocrine resistance of breast cancer, but its presence at both the mRNA and protein level suggest that it may, nevertheless, be involved in regulating the expression of oestrogen-responsive genes in breast cancer.

Adult↗
PubMed1997

Fibroblast growth factor 2 in breast cancer: occurrence and prognostic significance.

This paper examines the expression of fibroblast growth factor 2 (FGF-2) in the malignant human breast. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was used to assess the level of expression of FGF-2 in a series of 51 patients clinically followed up for a median of 84 months (Luqmani et al, 1992). Immunohistochemistry and Western blotting were used to show that the level of FGF-2 in breast tissues correlated with the amount of FGF-2 mRNA. FGF-2 was present in both malignant and non-malignant breast, although less was expressed in malignant tissues as determined by all three methods. Immunohistochemistry on frozen sections of breast tissue showed expression of FGF-2 in myoepithelial and epithelial cells in non-malignant samples and generally lower or undetectable levels of staining in malignant epithelial cells. The results obtained by immunohistochemistry correlated well with RT-PCR data showing similar levels of FGF-2 and FGF-2 mRNA expression in samples. No correlation was found between FGF-2 mRNA expression and T stage, nodal status or oestrogen receptor status. However, Kaplan-Meier survival plots show that higher levels of FGF-2 are associated with improved overall and disease-free survival. We suggest that FGF-2 expression may have value as a prognostic indicator in breast cancer.

Adult↗
PubMed1996

Expression of FGFR2 BEK and K-SAM mRNA variants in normal and malignant human breast.

The expression of mRNA encoding alternative forms of fibroblast growth factor receptor 2 (FGFR2) differing in the carboxy terminal half of their third immunoglobulin-like domain, was investigated in 77 human breast cancer tissues, 12 non-malignant breast biopsies and 29 cell lines, using a reverse transcriptase (RT) polymerase chain reaction (PCR) method. RNA from the two tissue groups yielded PCR product corresponding to both the BEK and the K-SAM form; amounts normalised to glyceraldehyde phosphate dehydrogenase product were similar in both groups. The level of either variant or of the total FGFR2 product was essentially unrelated to prognosis or clinical status except that patients with advanced clinical T staging had a higher proportion of BEK to K-SAM (P = 0.01). RNA from 1/2 normal breast derived and 8/10 breast cancer cell lines expressed exclusively or predominantly the K-SAM form; 2/10 had significant amounts of both BEK and K-SAM mRNA. Of 12 other epithelial lines, seven expressed mainly K-SAM mRNA, four expressed BEK and one was negative. Of five non-epithelial lines, one was negative, two expressed only BEK mRNA and two had significant amounts of both variants. We conclude that tissue levels of FGFR2 mRNA are unaltered in breast cancer extracts and that the splicing mechanism for this exon selection appears not to be significantly disrupted.

Adult↗
PubMed1996

Differential expression of gp200-MR6 molecule in benign hyperplasia and down-regulation in invasive carcinoma of the breast.

In this study, we used immunohistochemical and biochemical analysis to show that gp200-MR6, a 200 kDa molecule that is functionally associated with the human interleukin 4 (IL-4) receptor complex, is expressed at high levels on normal breast epithelial tissues, at lower levels on in situ carcinomas, and that the expression is lost in the invasive carcinoma of the breast. Furthermore, a preliminary study showed that benign epithelial hyperplasia of the breast expresses the gp200-MR6 heterogeneously. Two populations of cells have been observed: MR6 positive and MR6 negative. Interestingly, MR6-positive cells were observed to have different morphology from those that were MR6 negative; the nuclei of the former were larger and rounded in shape, whereas the nuclei of the latter were relatively small and oval in shape. In sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, monoclonal antibody MR6 detects the same molecular weight molecule in both normal and transformed tissue, indicating that the molecule is not a product of a truncated gene. The intensity of the gp200-MR6 bands correlates with the immunohistochemical data, indicating that the molecule is expressed at high levels in normal tissue and at lower levels in malignant tissue. These results suggest that analysis of gp200-MR6 expression may be useful in tumour grading and prognostic evaluation in breast cancer. Moreover, the molecule may be involved early in the process of tumorigenesis of the breast, in which a loss or a down-regulation of gp200-MR6 could contribute towards tumour development and progression via an effect on cell growth and differentiation.

Antigens, CD↗
PubMed1995

Expression of 2 variant forms of fibroblast growth factor receptor 1 in human breast.

The expression of variant mRNAs encoding isoforms of fibroblast growth factor receptor (FGFR)1 with either 2 or 3 Ig-like loops in the extracellular domain was investigated in human breast tissues and cell lines using a polymerase chain reaction amplification method. Almost all tissues contained both forms of FGFR1, but cancers (n = 137) had a significantly lower proportion of the transcript that encoded the full 3-loop form compared with non-malignant biopsies (n = 34). This was confirmed using microdissected populations of normal and cancerous cells from frozen tissue sections. A high ratio of the 2- to 3-loop form was found to be predictive of reduced relapse-free survival. In both groups, however, the predominant form of FGFR1 was that encoding the 2-loop receptor. Cell lines derived from a variety of tissues, including breast, also co-expressed both variants of FGFR1, suggesting their presence within the same cell type. Again, there was a similar preponderance of the shorter isoform. Our results were confirmed at the protein level, where out of 5 cancers analysed 4 expressed more of the 2-loop form than the 3-loop form. Our findings suggest that cells may normally simultaneously express several splice variants of FGFR1, and aberrant expression or a change in their relative amounts (i.e., in malignancy) could contribute to modified responses to either autocrine or paracrine factors.

Adult↗
PubMed1995

Expression of fibroblast growth factor 1 is lower in breast cancer than in the normal human breast.

We have measured the amount of fibroblast growth factor 1 (FGF-1) mRNA and protein in primary breast cancers and non-malignant breast tissue and have found greatly reduced levels in breast cancer compared with non-malignant tissue. A total of 116 breast cancers and 37 biopsies taken from non-malignant breast were compared for FGF-1 mRNA expression using reverse transcriptase-polymerase chain reaction (RT-PCR) and significantly lower levels were found in the cancer tissues (P < 0.001). These findings were confirmed at the protein level where four out of five breast cancers contained no detectable FGF-1 and a fifth cancer had a low level of FGF-1 compared with three samples from reduction mammoplasties. Similar results were obtained from breast cell lines in which 80% of cancer cell lines had very low levels of FGF-1, whereas all non-malignant breast cell lines contained higher levels of FGF-1. Immunohistochemical analysis indicated that FGF-1 was present in the luminal epithelial cells of the non-malignant breast but was absent from cancer cells. The decreased levels of FGF-1 in breast cancer may indicate that stimulation of cancer cells is resulting in down-regulation of FGF-1 expression or may implicate FGF-1 as a differentiation factor rather than a growth factor at its physiological concentration in the breast.

Adult↗
PubMed1994

Subtraction hybridization cloning of RNA amplified from different cell populations microdissected from cryostat tissue sections.

We describe a generally applicable and easily reproducible method for the cloning of differentially expressed RNA, amplified from small numbers of enriched cell populations, obtained by microdissection from single cryostat sections. The procedure involves homopolymeric A tailing of cDNA synthesized from released RNA using an anchored (NN)T12 primer. Subsequent entire cDNA population polymerase chain reaction amplification was carried out using a biotinylated (X)nT16 primer-adaptor in the presence of biotin-dATP. This biotinylated driver cDNA was then twice hybridized in 50-fold excess to heterologous target cDNA made with nonbiotinylated (Y)nT16 primer; common hybrids and excess driver cDNA were magnetically removed following the addition of streptavidin-coated magnetospheres which bound biotinylated strands, leaving enriched target population sequences. These were then directly amplified through the tails using a primer containing only the target-specific (Y)n sequence. Insertion into a lambda-phage vector was facilitated by means of an EcoR1 site incorporated in the (Y)n primer. Subsequent packaging and transformation into Escherichia coli NM522 resulted in cDNA libraries containing approximately 5 x 10(3)-10(4) pfu. Screening of these primary libraries with cDNA derived from the starting populations yielded a large number of differentially hybridizing clones which are currently under analysis.

Base Sequence↗