Proliferation-dependent expression and phosphorylation of pRB in B cell non-Hodgkin's lymphomas: dependence on RB1 copy number.
Some studies have suggested that a significant fraction of non-Hodgkin's lymphomas (NHL) do not express pRB protein, possibly due to deletions of RB1. We examined RB1/centromere 17 copy number by fluorescent in situ hybridisation, and pRB expression/phosphorylation by immunohistochemistry (IHC) and immunoblotting (IB) in 66 cases of B cell NHL. Thirteen cases had lost one RB1 copy relative to centromere 17 copy number and total DNA content. Case 458/88 had no RB1 copies. pRB levels were heterogeneous as assessed by IB (0.04-1.12 relative units), but all tumours, except for case 458/88, expressed pRB localised to the nucleus in >75% of the tumour cells by IHC. The fraction of phosphorylated pRB was correlated with pRB expression (r(2)= 0.56, P < 0.001). The 14 cases with loss of RB1 had lower pRB expression (median 0.25) than those without (median 0.48, P < 0.001), but a correlation with S phase fraction (r(2) = 0.43, P < 0.001; previously published data for tumour-specific S phase and apoptotic fractions) indicated that the variation in pRB expression was due to differences in proliferative activity. Furthermore, the regression lines for pRB expression vs S phase fraction were not different for the cases with or without loss of one RB1 copy (P = 0.5). Cases 154/88 (one RB1 copy) and 258/88 (two RB1 copies), in addition to case 458/88, had low expression of (hypophosphorylated) pRB (0.04, 0.08 and 0.04), despite their high S phase fractions (21%, 17% and 21%). There was no association between pRB expression/RB1 copy number and apoptotic fraction. Neither pRB expression nor loss of RB1 had prognostic value, but cases 154/88, 258/88, and 458/88 had short survival times (5, 3 and 46 months, respectively) compared to the others (median survival: 44 months, P = 0.03). It is suggested that pRB expression and function are normal in 63 of 66 NHL cases, including 12 of 13 lymphomas with loss of one RB1 allele.
Galteland
E
E
Department of Biophysics, The Norwegian Radium Hospital, Oslo, Norway.
Smedshammer
L
L
Suo
Z
Z
DeAngelis
P
P
Stokke
T
T
D000483:Alleles; D017209:Apoptosis; D015153:Blotting, Western; D002453:Cell Cycle; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002877:Chromosomes, Human / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics; D017353:Gene Deletion; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic; D016161:Genes, Retinoblastoma; D019942:Genes, p16; D006801:Humans; D007124:Immunoenzyme Techniques; D017404:In Situ Hybridization, Fluorescence; D008228:Lymphoma, Non-Hodgkin / Q000235:genetics* / Q000378:metabolism / Q000401:mortality / Q000473:pathology; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D011379:Prognosis; D011499:Protein Processing, Post-Translational; D016160:Retinoblastoma Protein / Q000096:biosynthesis / Q000502:physiology*
D009363:Neoplasm Proteins; D016160:Retinoblastoma Protein; D019938:Cyclin D1