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Stem cell markers: ABCG2 and MCM2 expression in retinoblastoma

A Mohan¹, M Kandalam¹, H L Ramkumar², L Gopal³ and S Krishnakumar⁴

¹ Department of Ocular Pathology, Vision Research Foundation, Chennai, Tamil Nadu, India
² Department of Biological Sciences, Northwestern University, Evanston, IL, USA
³ Vitreoretina Services, Vision Research Foundation, Chennai, Tamil Nadu, India
⁴ Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, Chennai, India

Correspondence to:
Correspondence to:
Dr Subramanian Krishnakumar
Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, 18, College Road, Chennai – 600 006, Tamil Nadu, India; drkrishnakumar_2000{at}yahoo.com

Backgound/aim: The authors studied the expression of cancer stem cell surface marker, ABCG2, and neural stem cell marker, MCM2, in retinoblastoma and correlated clinicopathologically.

Methods: Among 39 retinoblastomas, 18 tumours were not subjected to preoperative/postoperative chemotherapy, 15 tumours underwent postoperative chemotherapy, and six tumours had preoperative chemotherapy. There were 20 tumours with no invasion and 19 tumours with invasion of choroid/optic nerve. ABCG2 and MCM2 expression was studied by immunohistochemistry.

Results: ABCG2 was positive in six of six and MCM2 was positive in five of six tumours that had recurred in the orbit or metastasised. ABCG2 was positive in 15/19 tumours with invasion. MCM2 was positive in 16/19 tumours with invasion. Invasive tumours showed higher expression of ABCG2 (p<0.01) and MCM2 (p<0.01) proteins. There was no correlation with differentiation and laterality of the tumours. Non-neoplastic retina was positive for ABCG2 and MCM2.

Conclusion: ABCG2 and MCM2 were expressed more in invasive tumours. Further studies are needed to understand the significance of ABCG2 and MCM2 expression in retinoblastoma.

Abbreviations: ABC, ATP binding cassette; DLP, diode laser photocoagulation; EBRT, external beam radiation therapy; LSAB, labelled streptavidin biotin; MCM, minichromosome maintenance; PBS, phosphate buffered saline; TCC, transconjunctival cryopexy

Keywords: stem cell markers; retinoblastoma; chemotherapy; drug resistance

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