Tumor Biology

, Volume 36, Issue 8, pp 6485–6496 | Cite as

Protein expression and methylation of MGMT, a DNA repair gene and their correlation with clinicopathological parameters in invasive ductal carcinoma of the breast

  • Asia Asiaf
  • Shiekh Tanveer Ahmad
  • Ajaz Ahmad Malik
  • Shiekh Aejaz Aziz
  • Zubaida Rasool
  • Akbar Masood
  • Mohammad Afzal Zargar
Research Article

Abstract

Epigenetic mechanisms such as DNA methylation are being increasingly recognized to play an important role in cancer and may serve as a cancer biomarker. The aim of this study was to evaluate the promoter methylation status of MGMT (O6-methylguanine-DNA methyltransferase) and a possible correlation with the expression of MGMT and standard clinicopathological parameters in invasive ductal breast carcinoma patients (IDC) of Kashmir. Methylation-specific PCR was carried out to investigate the promoter methylation status of MGMT in breast tumors paired with the corresponding normal tissue samples from 128 breast cancer patients. The effect of promoter methylation on protein expression in the primary breast cancer and adjacent normal tissues was evaluated by immunohistochemistry (n = 128) and western blotting (n = 30). The frequency of tumor hypermethylation was 39.8 % and a significant difference in methylation frequency among breast tumors were found (p < 0.001) when compared with the corresponding normal tissue. Immunohistochemical analysis showed no detectable expression of MGMT in 68/128 (53.1 %) tumors. MGMT promoter methylation mediated gene silencing was associated with loss of its protein expression (rs = −0.285, p = 0.001, OR = 3.38, 95 % CI = 1.59–7.17). A significant correlation was seen between loss of MGMT and lymph node involvement (p = 0.030), tumor grade (p < 0.0001), loss of estrogen receptors (ER; p = 0.021) and progesterone receptors (PR) (p = 0.016). Also, MGMT methylation was found to be associated with tumor grade (p = 0.011), tumor stage (p = 0.009), and loss of ER (p = 0.003) and PR receptors (p = 0.009). To our knowledge, our findings, for the first time, in Kashmiri population, indicate that MGMT is aberrantly methylated in breast cancer and promoter hypermethylation could be attributed to silencing of MGMT gene expression in breast cancer. Our data suggests that MGMT promoter hypermethylation could have a potential function as molecular biomarker of breast oncogenesis. Also, based on their predictive value of response to therapy, the immunohistochemical evaluation and interpretation of MGMT may also help in future to establish therapeutic strategies for patients with breast cancer.

Keywords

Breast cancer Promoter methylation MGMT MSP Kashmir 

Notes

Acknowledgments

The authors are thankful to the University Grants Commission (UGC), New Delhi, India, for providing the funds that allowed us to carry out this research.

Conflicts of interest

The contributing authors declare that they have no competing interests.

Supplementary material

13277_2015_3339_Fig6_ESM.gif (3.3 mb)
Supplementary Fig. 1

The upper panel of the representative images show HEK293 cells after 48 h of transient empty vector transfection (pB513B1) without human MGMT gene. These cells did not express MGMT as seen by the absence of MGMT antibody immunofluorescence. Whereas the human MGMT transfected (pB513B1-MGMT)HEK293 cells show strong nuclear immunofluorescence (green) as seen in the lower panel. (GIF 3384 kb)

13277_2015_3339_MOESM1_ESM.tif (49.9 mb)
High resolution image (TIFF 51055 kb)
13277_2015_3339_MOESM2_ESM.docx (12 kb)
ESM 2 (DOCX 11 kb)

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Copyright information

© International Society of Oncology and BioMarkers (ISOBM) 2015

Authors and Affiliations

  • Asia Asiaf
    • 1
  • Shiekh Tanveer Ahmad
    • 2
  • Ajaz Ahmad Malik
    • 3
  • Shiekh Aejaz Aziz
    • 4
  • Zubaida Rasool
    • 5
  • Akbar Masood
    • 1
  • Mohammad Afzal Zargar
    • 1
  1. 1.Department of Biochemistry, Faculty of Biological ScienceUniversity of KashmirSrinagarIndia
  2. 2.Clarke H. Smith Brain Tumour CentreUniversity of CalgaryCalgaryCanada
  3. 3.Department of General SurgerySher-I-Kashmir Institute of Medical SciencesSrinagarIndia
  4. 4.Department of Medical OncologySher-I-Kashmir Institute of Medical SciencesSrinagarIndia
  5. 5.Department of PathologySher-I-Kashmir Institute of Medical SciencesSrinagarIndia

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