Epidemiological and survival analysis of triple-negative breast cancer cases in a retrospective multicenter study.

INTRODUCTION: This is a retrospective study with data collected from breast cancer cases from five major Apollo Hospitals across India, as part of a biobanking process. One aspect of our study focused specifically on data from triple-negative breast cancer (TNBC) cases. The aim of this study was to analyze epidemiology, treatment options, and survival of the patients with TNBC. Our goal was to draw conclusions on the preponderance of the disease and also to understand the outcomes using the existing therapy options. MATERIALS AND METHODS: Data were collected after due ethical clearances and were coded with regard to patient identifiers to protect patient privacy. Data were not only from the various departments of the respective hospitals and the treating physicians but also from the follow-up made by hospital staff and social workers. RESULTS: About 20% of all cases of breast cancer comprised TNBC. Although the disease is generally thought to be an early onset disease, there was no major difference in the median age of diagnosis of TNBC compared to other breast cancer cases. More than 85% of the TNBC cases were of early stage disease with <4% of the cases of metastatic cancer. Data on follow-up were somewhat sporadic as a good number of cases were lost to follow-up, but from the available data, recurrence rate was about 11%. Death, when it occurred, was mostly in the early periods of treatment with 35% of the events occurring before 3 years. The overall survival rates beyond 3 years were more than 86%. CONCLUSIONS: Data and sample collection are an ongoing process, so we expect this data set to be enriched with more cases and longer duration of follow-up in a year. Preliminary analysis sheds light on the potential of such a collection both for understanding the epidemiology of the disease and also for conducting future studies with an eye toward improving treatment outcomes.

CXCR4 activation maintains a stem cell population in tamoxifen-resistant breast cancer cells through AhR signalling.

BACKGROUND: Tamoxifen is commonly used for breast cancer therapy. However, tamoxifen resistance is an important clinical problem. Continuous treatment with conventional therapy may contribute to cancer progression in recurring cancers through the accumulation of drug-resistant cancer progenitors. METHODS: To investigate signalling mechanisms important for the maintenance and viability of drug-resistant cancer progenitors, we used microarray analysis, PCR array for genes involved in cancer drug resistance and metabolism, flow cytometry, soft agar colony formation assay, in vivo tumourigenicity assay and immunohistochemical analysis using tamoxifen-sensitive and tamoxifen-resistant breast cancer MCF7 cells. RESULTS: Downregulation of CXCR4 signalling by small molecule antagonist AMD3100 specifically inhibits growth of progenitor cell population in MCF7(TAM-R) cells both in vitro and in vivo. Microarray analysis revealed aryl hydrocarbon receptor (AhR) signalling as one of the top networks that is differentially regulated in MCF7(TAM-R) and MCF7 xenograft tumours treated with AMD3100. Further, small molecule antagonists of AhR signalling specifically inhibit the progenitor population in MCF7(TAM-R) cells and growth of MCF7(TAM-R) xenografts in vivo. CONCLUSION: The chemokine receptor CXCR4 maintains a cancer progenitor population in tamoxifen-resistant MCF7 cells through AhR signalling and could be a putative target for the treatment of tamoxifen-resistant breast cancers.

Overexpression of TRIB2 in human lung cancers contributes to tumorigenesis through downregulation of C/EBPα.

Lung cancer is the most common cause of cancer-related mortality worldwide. Here, we report elevated expression of tribbles homolog 2 (TRIB2) in primary human lung tumors and in non-small cell lung cancer cells that express low levels of differentiation-inducing transcription factor CCAAT/enhancer-binding protein alpha (C/EBPα). In approximately 10-20% of cases, elevated TRIB2 expression resulted from gene amplification. TRIB2 knockdown was found to inhibit cell proliferation and in vivo tumor growth. In addition, TRIB2 knockdown led to morphological changes similar to C/EBPα overexpression and correlated with increased expression and activity of C/EBPα. TRIB2-mediated regulation of C/EBPα was found to occur through the association of TRIB2 with the E3 ligase TRIM21. Together, these data identify TRIB2 as a potential driver of lung tumorigenesis through a mechanism that involves downregulation of C/EBPα.

PU.1 binding to the p53 family of tumor suppressors impairs their transcriptional activity.

The transcription factor PU.1 is essential for terminal myeloid differentiation, B- and T-cell development, erythropoiesis and hematopoietic stem cell maintenance. PU.1 functions as oncogene in Friend virus-induced erythroleukemia and as tumor suppressor in acute myeloid leukemias. Moreover, Friend virus-induced erythroleukemia requires maintenance of PU.1 expression and the disruption of p53 function greatly accelerates disease progression. It has been hypothesized that p53-mediated expression of the p21(Cip1) cell cycle inhibitor during differentiation of pre-erythroleukemia cells promotes selection against p53 function. In addition to the blockage of erythroblast differentiation provided by increased levels of PU.1, we propose that PU.1 alters p53 function. We demonstrate that PU.1 reduces the transcriptional activity of the p53 tumor suppressor family and thus inhibits activation of genes important for cell cycle regulation and apoptosis. Inhibition is mediated through binding of PU.1 to the DNA-binding and/or oligomerization domains of p53/p73 proteins. Lastly, knocking down endogenous PU.1 in p53 wild-type REH B-cell precursor leukemia cells leads to increased expression of the p53 target p21(Cip1).

Identification of the p53 family-responsive element in the promoter region of the tumor suppressor gene hypermethylated in cancer 1.

The tumor suppressor gene hypermethylated in cancer 1 (HIC1), located on human chromosome 17p13.3, is frequently silenced in cancer by epigenetic mechanisms. Hypermethylated in cancer 1 belongs to the bric à brac/poxviruses and zinc-finger family of transcription factors and acts by repressing target gene expression. It has been shown that enforced p53 expression leads to increased HIC1 mRNA, and recent data suggest that p53 and Hic1 cooperate in tumorigenesis. In order to elucidate the regulation of HIC1 expression, we have analysed the HIC1 promoter region for p53-dependent induction of gene expression. Using progressively truncated luciferase reporter gene constructs, we have identified a p53-responsive element (PRE) 500 bp upstream of the TATA-box containing promoter P0 of HIC1, which is sequence specifically bound by p53 in vitro as assessed by electrophoretic mobility shift assays. We demonstrate that this HIC1 p53-responsive element (HIC1.PRE) is necessary and sufficient to mediate induction of transcription by p53. This result is supported by the observation that abolishing endogenous wild-type p53 function prevents HIC1 mRNA induction in response to UV-induced DNA damage. Other members of the p53 family, notably TAp73beta and DeltaNp63alpha, can also act through this HIC1.PRE to induce transcription of HIC1, and finally, hypermethylation of the HIC1 promoter attenuates inducibility by p53.

Identification of an active-site residue in yeast invertase by affinity labeling and site-directed mutagenesis.

Deglycosylated yeast invertase is irreversibly inactivated by conduritol B epoxide (CBE), an active-site-directed reagent. The inactivated enzyme contained 0.8 mol of CBE/mol of invertase monomer suggesting that the inactivation results from the modification of a single amino acid residue. Peptic digestion of [3H]CBE-labeled invertase followed by reverse phase column chromatography yielded two labeled peptides, both located at the amino-terminal end of the enzyme. Sequence analyses of these peptides revealed that Asp-23 is the modified residue. The role of Asp-23 in the catalytic process was investigated by changing it to Asn using site-directed mutagenesis of the SCU2 gene. The mutant enzyme was basically inactive, confirming a role for Asp-23 in the catalytic process.

Characterization of the glycosylation sites in yeast external invertase. I. N-linked oligosaccharide content of the individual sequons.

External invertase is the product of the SUC2 gene of Saccharomyces cerevisiae. The deduced sequence of this enzyme (Taussig, R., and Carlson, M. (1983) Nucleic Acid Res. 11, 1943-1954) reveals it to contain 14 potential N-linked glycosylation sites, or sequons, although only 9-10 appear to be glycosylated (Trimble, R. B., and Maley, F. (1977) J. Biol. Chem. 252, 4409-4412). To determine the location of the glycosylated sequons, external invertase was deglycosylated with endo-beta-acetylglucosaminidase H and its component peptides analyzed by both fast atom bombardment mass spectrometry (FABMS) and classical peptide isolation procedures. By use of the former technique most of the glucosamine-containing sequons could be located and by the latter sufficient amounts of small glucosamine-containing peptides were isolated to enable their quantitation. From the combined FABMS and glucosamine analyses, it was established that eight of the sequons in a subunit of invertase are either completely or almost completely glycosylated, while five others are glycosylated to the extent of about 50% or less. In the case of two overlapping sequons (4 and 5), which include Asn92-Asn93-Thr-Ser, only the first Asn was glycosylated. Thus, all but one of the sequons of external invertase are glycosylated to some extent, giving an appearance of only 9-10 N-linked oligosaccharides/subunit. The sequence identity of both external and internal invertase was verified by FABMS and by peptide sequence analysis. In only one site was an amino acid found to differ from that deduced from the DNA sequence of the SUC2 gene. This occurred at position 390 where a proline was found in place of alanine, which could result from a single base change in the triplet specifying the latter amino acid.

Riboflavin, folate and vitamin C status of Gambian women during pregnancy: a comparison between urban and rural communities.

Anthropometric, haematological and vitamin status indices were measured in a group of pregnant women living in the urban community of Bakau in The Gambia, West Africa. Their haematological and anthropometric indices were generally within normal limits. Vitamin C status was also acceptable and was similar to values observed in rural Gambian women sampled at the same time of year. Folate status was similar to that seen previously in rural Gambian communities, and there was a strong intrasubject correlation between plasma and red cell folate levels, together with a trend towards higher values as pregnancy progressed. This was consistent with probable compliance with local recommendations for folate supplementation during pregnancy. The urban Gambian women also resembled their rural counterparts in having very poor biochemical riboflavin status, which deteriorated as pregnancy progressed. In this respect they differed markedly from UK women, who had satisfactory riboflavin status even in late pregnancy. The existence of severe biochemical riboflavin deficiency, even in urban Gambian women, whose anthropometric indices are not compatible with severe general malnutrition, suggests that a deficiency of this vitamin may be widespread in Sahelian West Africa. Measures to improve maternal vitamin status during pregnancy would therefore be equally appropriate in both rural and urban communities.

Atypical reaction of 'essential' sulfhydryl groups of malic enzyme with 2-nitro-5-thiocyanobenzoate and 2,4-dinitrophenylthiocyanate.

Under protective conditions N-ethylmaleimide irreversibly blocks most of the nonessential SH groups of pigeon liver malic enzyme (EC 1.1.1.40) leaving the oxidative decarboxylase activity intact. Reaction between the resultant prereacted enzyme and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) leads to the modification of about seven SH residues/tetramer, of which four fast-reacting groups constitute the 'essential' groups responsible for the loss of oxidative decarboxylase activity. 2-Nitro-5-thiocyanobenzoate (NTCB) reacts atypically with the prereacted enzyme by substituting the four 'essential' SH residues with one cyano residue and three 2-nitro-5-thiobenzoate residues. The resulting enzyme derivative is 90% inactive. The cyanoenzyme derivative produced by cyanolysis of DTNB-modified prereacted enzyme or NTCB-modified prereacted enzyme has all four 'essential' SH groups substituted with cyano groups and possesses half of the original activity. Modification of prereacted enzyme by 2,4-dinitrophenylthiocyanate (DNPT), in contrast to NTCB, results in unequal substitution of the 'essential' residues with cyano residues and a single 2,4-dinitrophenyl residue. Dithiothreitol reactivates the DNPT-modified prereacted enzyme by regenerating three 'essential' SH residues, but failed to release the dinitrophenyl residue. The atypical reactions of prereacted enzyme with NTCB or DNPT require that the native conformation of the enzyme be retained, since these reagents react by substituting the SH groups of urea-denatured enzyme with only cyano groups.