Ten-year survival outcome of breast cancer patients in India

INTRODUCTION:

Breast cancer is the most frequently diagnosed cancer among women in India; however, there are no studies addressing long-term survival (10 years and above). This study sought to evaluate long-term oncological outcome among women with breast cancer treated with a curative intent.

MATERIALS AND METHODS:

This is a retrospective cohort analysis of 1301 breast cancer patients of all stages who had received primary treatment with curative intent from 2004 to 2010 at a single cancer institution of India.

RESULTS:

A total of 1301 breast cancer patients were available for final analysis. The median age was 51 years (range, 21–86 years). 70.25% of the patients had early breast cancer (EBC), 21.9% had locally advanced breast cancer, and 7.85% of the patients with de novo metastatic disease also underwent surgery. 56.5% of the patients had hormone-sensitive tumors, human epidermal growth factor receptor 2 over expression was seen in 17%, and triple-negative tumors accounted for 26.2% of the patients. The 5- and 10-year overall survival (OS) of the entire cohort was 79% and 66%, and the 5- and 10-year breast cancer-specific survival (BCSS) was 79% and 70%, respectively. OS and BCSS were 51% and 58%, respectively, at 15-year follow-up after primary cancer treatment. On multivariate analysis, the factors associated with prolonged survival were age ≤50 years, EBC, and treatment during the later period (2008–2010).

CONCLUSION:

Difference between OS and BCSS was found to have an increasing trend during 10–15-year follow-up, the difference being 4% at 10 years and 7% at 15 years. Age ≤50 years, early-stage disease at presentation, and primary cancer treatment in later years (2008–2010) were favorable predictors for 10-year survival.

Effect of signal peptide on the stability and folding kinetics of maltose binding protein

While the role of the signal sequence in targeting proteins to specific subcellular compartments is well characterized, there are fewer studies that characterize its effects on the stability and folding kinetics of the protein. We report a detailed characterization of the folding kinetics and thermodynamic stabilities of maltose binding protein (MBP) and its precursor form, preMBP. Isothermal GdmCl and urea denaturation as a function of temperature and thermal denaturation studies have been carried out to compare stabilities of the two proteins. preMBP was found to be destabilized by about 2-6 kcal/mol (20-40%) with respect to MBP. Rapid cleavage of the signal peptide by various proteases shows that the signal peptide is accessible in the native form of preMBP. The observed rate constant of the major slow phase in folding was decreased 5-fold in preMBP relative to MBP. The rate constants of unfolding were similar at 25 degrees C, but preMBP also exhibited a large burst phase change in unfolding that was absent in MBP. At 10 degrees C, preMBP exhibited a higher unfolding rate than MBP as well as a large burst phase. The appreciable destabilization of MBP by signal peptide is functionally relevant, because it enhances the likelihood of finding the protein in an unfolded translocation-competent form and may influence the interactions of the protein with the translocation machinery. Destabilization is likely to result from favorable interactions between the hydrophobic signal peptide and other hydrophobic regions that are exposed in the unfolded state.

Electron spin resonance and fluorescence studies of the bound-state conformation of a model protein substrate to the chaperone SecB

SecB is a homotetrameric, cytosolic chaperone that forms part of the protein translocation machinery in Escherichia coli. We have investigated the bound-state conformation of a model protein substrate of SecB, bovine pancreatic trypsin inhibitor (BPTI) as well as the conformation of SecB itself by using proximity relationships based on site-directed spin-labeling and pyrene fluorescence methods. BPTI is a 58-residue protein and contains three disulfide groups between residues 5 and 55, 14 and 38, as well as 30 and 51. Mutants of BPTI that contained only a single disulfide were reduced, and the free cysteines were labeled with either thiol-specific spin labels or pyrene maleimide. The relative proximity of the labeled residues was studied using either electron spin resonance spectroscopy or fluorescence spectroscopy. The data suggest that SecB binds a collapsed coil of reduced unfolded BPTI, which then undergoes a structural rearrangement to a more extended state upon binding to SecB. Binding occurs at multiple sites on the substrate, and the binding site on each SecB monomer accommodates less than 21 substrate residues. In addition, we have labeled four solvent-accessible cysteine residues in the SecB tetramer and have investigated their relative spatial arrangement in the presence and absence of the substrate protein. The electron spin resonance data suggest that these cysteine residues are in close proximity (15 A) when no substrate protein is bound but move away to a distance of greater than 20 A when SecB binds substrate. This is the first direct evidence of a conformational change in SecB upon binding of a substrate protein.