Missing expression of pRb2/p130 in human retinoblastomas is associated with reduced apoptosis and lesser differentiation.
OBJECTIVE
Although the retinoblastoma gene (RB/p105) has been intensely investigated as a prototype suppressor gene in humans, mutational data on the Rb family member pRb2/p130 (p130) has only recently been reported. A protective role against apoptosis has been suggested for pRb/p105, both in vitro and in vivo. However, only limited information is available on the role of pRb2/p130 in controlling apoptosis. The purpose of this study was to determine the extent of a role of this gene in the neoplasms that give the Rb family its name.


METHODS
Forty-two human retinoblastomas were retrospectively examined by immunohistochemical labeling of the Rb-related proteins and the results compared with cellular kinetic characteristics: the apoptotic index (AI) and the mitotic index (MI).


RESULTS
The retinoblastomas that did not express p130 showed a significantly lower AI than those that expressed p130. This result was also supported by flow cytometry on a human Saos-2 cell line that was transiently transfected with RB2/p130. The p130(-) tumors displayed a lesser degree of differentiation than the p130(+) ones.


CONCLUSIONS
These observations give evidence that expression of p130 is inversely correlated with higher rates of apoptosis in human retinoblastomas and give an additional example of this regulator's role in cellular differentiation.
Bellan
Cristiana
C
Institute of Pathologic Anatomy and Histology, University of Siena, Italy.
De Falco
Giulia
G
Tosi
Gian Marco
GM
Lazzi
Stefano
S
Ferrari
Filomena
F
Morbini
Giovanna
G
Bartolomei
Sabrina
S
Toti
Paolo
P
Mangiavacchi
Paola
P
Cevenini
Gabriele
G
Trimarchi
Carmela
C
Cinti
Caterina
C
Giordano
Antonio
A
Leoncini
Lorenzo
L
Tosi
Piero
P
Cottier
Hans
H
D017209:Apoptosis; D015153:Blotting, Western; D002452:Cell Count; D002454:Cell Differentiation; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D007223:Infant; D008297:Male; D008940:Mitotic Index; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011506:Proteins; D012160:Retina / Q000378:metabolism; D019572:Retinal Neoplasms / Q000378:metabolism* / Q000473:pathology*; D012175:Retinoblastoma / Q000378:metabolism* / Q000473:pathology*; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism; D050717:Retinoblastoma-Like Protein p130; D012189:Retrospective Studies; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology
D010750:Phosphoproteins; D011506:Proteins; C493837:RBL2 protein, human; D016160:Retinoblastoma Protein; D050717:Retinoblastoma-Like Protein p130