Multidrug resistant proteins: P-glycoprotein and lung resistance protein expression in retinoblastoma.
OBJECTIVE
Retinoblastoma is the commonest primary intraocular tumour in children. Chemotherapy now plays a big part in the treatment of these tumours. There is not much information about the role of the multidrug resistance proteins (MDR)-P-glycoprotein (P-gp) and vault protein lung resistance protein (LRP)-in retinoblastoma. The authors investigated the expression of P-gp and LRP in retinoblastoma and correlated them clinicopathologically.


METHODS
Among 60 retinoblastomas, 40 tumours were not subjected to preoperative or postoperative chemotherapy and 20 tumours were subjected to postoperative chemotherapy. In this cohort 27 tumours had no invasion and 33 tumours had invasion of choroid, optic nerve, and orbit. P-gp and LRP expression were studied by immunohistochemistry. Immunoanalysis was done semiquantitatively.


RESULTS
Among the 60 tumours P-gp was expressed in 23 (38%) tumours and LRP was expressed in 35 (58%). P-gp was expressed in 11/27 (40%) tumours with no invasion and in 12/33 (36%) tumours with invasion. LRP was expressed in 15/27 (55%) tumours with no invasion and in 20/33 (60%) tumours with invasion. Both P-gp and LRP were negative in three tumours with invasion, which had later developed bone marrow metastasis. There was no correlation between P-gp and LRP expression with invasion, differentiation and laterality of the tumours and response to treatment.


CONCLUSIONS
Retinoblastoma expresses P-gp and LRP intrinsically before chemotherapy and none of these proteins predicted the response to chemotherapy. Thus, further studies are needed to understand the significance of the expression of the P-gp and LRP proteins in retinoblastoma.
Krishnakumar
S
S
Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, 18 College Road, Chennai-600 006,Tamil Nadu, India. drkrishnakumar_2000@yahoo.com
Mallikarjuna
K
K
Desai
N
N
Muthialu
A
A
Venkatesan
N
N
Sundaram
A
A
Khetan
V
V
Shanmugam
M P
MP
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis*; D019046:Bone Marrow Neoplasms / Q000556:secondary; D002648:Child; D002675:Child, Preschool; D018432:Drug Resistance, Multiple; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007223:Infant; D008297:Male; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000032:analysis*; D019572:Retinal Neoplasms / Q000737:chemistry / Q000188:drug therapy* / Q000473:pathology; D012175:Retinoblastoma / Q000737:chemistry / Q000188:drug therapy* / Q000473:pathology; D016896:Treatment Outcome; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D009363:Neoplasm Proteins; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein