👤 S Bindhya

The gene for receptor tyrosine kinase ErbB2 is amplified in breast and ovarian tumours. The linear pathway by which signals are transduced through ErbB2 are well known. However, second generation questions that address spatial aspects of signaling remain. To address this, we have undertaken a mass spectrometry approach to identify phosphoproteins specific for ErbB2 using the inhibitors Lapatinib and CP724714 in ovarian cancer cells. The ErbB2 specific proteins identified in SKOV-3 cells were Myristoylated alanine-rich C-kinase substrate, Protein capicua homolog, Protein peptidyl isomerase G, Protein PRRC2C, Chromobox homolog1 and PRP4 homolog. We have evaluated three phosphoproteins PKM2, Aldose reductase and MARCKS in SKOV-3 cells. We observed that PKM2 was phosphorylated by EGF but was not inhibited by Lapatinib and CP724714. The activity of aldose reductase in reducing NADPH as a substrate was significantly higher in EGF stimulated cells which was inhibited by Lapatinib and CP724714 but not by Geftinib (EGFR inhibitor). MARCKS was phosphorylated on stimulation of SKOV-3 cells with EGF that was inhibited by Lapatinib and CP724714 which was dependent on the kinase activity of ErbB2. These results have identified phosphoproteins that are specific to ErbB2 which have not been previously reported and sets the basis for future experiments. Show less

Cardiotoxicity is the most serious side effect of anthracyclines (doxorubicin, daunorubicin or epirubicin). The incidence of anthracycline induced late cardiac toxicity (AIC) that is overt clinically is 3-5% in the Indian population. Polymorphism in intron 32 (deletion of 25bp) of MYBPC3 has been shown to be present exclusively in Asians and more so in South India (3-8%). The frequency of the polymorphism is significantly higher (13%) in patients with cardiomyopathy in India. Fifteen patients were identified to have cardiac dysfunction following treatment for malignant lymphoma with doxorubicin containing regimens. Peripheral blood DNA from control, amplified by polymerase chain reaction yielded a 467bp fragment while in the presence of the 25bp deletion only a 442bp fragment was detected. To confirm the presence or absence of the polymorphism, amplified DNA was restricted using Bgl1 in all samples. Bgl1 restricted amplified DNA only if the 25bp deletion was absent. A 467 base pair band was observed in all the 15 samples, which suggested the absence of polymorphism in MYBPC3. In a sample of DNA from a patient with a deletion in exon 33 (confirmed by sequencing) a 442bp fragment was detected. Amplified DNA from this patient was not restricted with Bgl1. Wild type MYBPC3 when amplified gave a distinct restriction banding pattern consisting of two bands of 401bp and 66bp. Amplified DNA from all peripheral blood samples restricted with Bgl1 suggesting the absence of the polymorphism. In this preliminary report, MYBPC3 does not seem to play a role in anthracycline induced cardiotoxicity. Show less