The bmi-1 oncoprotein is differentially expressed in non-small cell lung cancer and correlates with INK4A-ARF locus expression.
Genes of the polycomb group function by silencing homeotic selector genes that regulate embryogenesis. In mice, downregulation of one of the polycomb genes, bmi-1, leads to neurological alterations and severe proliferative defects in lymphoid cells, whilst bmi-1 overexpression, together with upregulation of myc-1, induces lymphoma. An oncogenic function has been further supported in primary fibroblast studies where bmi-1 overexpression induces immortalization due to repression of p16/p19ARF, and where together with H-ras, it readily transforms MEFs. It was the aim of this study to assess the expression of bmi-1 in resectable non-small cell lung cancer (NSCLC) in association with p16 and p14ARF (=human p19ARF). Tumours (48 resectable NSCLC (32 squamous, 9 adeno-, 2 large cell, 4 undifferentiated carcinomas and 1 carcinoid); stage I, 29, II, 7, III, 12; T1, 18, T2, 30; differentiation: G1 12, G2 19, G3 17) were studied by immunohistochemistry for protein expression and by comparative multiplex PCR for gene amplification analysis. In tumour-free, normal lung tissue from patients, weak - moderate bmi-1 staining was seen in some epithelial cells, lymphocytes, glandular cells and in fibroblasts, whereas blood, endothelial, chondrocytes, muscle cells and adipocytes did not exhibit any bmi-1 expression. In tumours, malignant cells were negative/weakly, moderately and strongly positive in 20, 22 and 6 cases, respectively. As assessed by multiplex PCR, bmi-1 gene amplification was not the reason for high-level bmi-1 expression. Tumours with moderate or strong bmi-1 expression were more likely to have low levels of p16 and p14ARF (P = 0.02). Similarly, tumours negative for both, p16 and p14ARF, exhibit moderate-strong bmi-1 staining. 58% of resectable NSCLC exhibit moderate-high levels of bmi-1 protein. The inverse correlation of bmi-1 and the INK4 locus proteins expression (p16/p14ARF) supports a possible role for bmi-1 misregulation in lung carcinogenesis.
Vonlanthen
S
S
Department of Clinical Research, University of Bern, Switzerland.
Heighway
J
J
Altermatt
H J
HJ
Gugger
M
M
Kappeler
A
A
Borner
M M
MM
van Lohuizen
M
M
Betticher
D C
DC
D000368:Aged; D014408:Biomarkers, Tumor; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000401:mortality / Q000473:pathology / Q000601:surgery; D002460:Cell Line; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D005260:Female; D006801:Humans; D008168:Lung / Q000166:cytology / Q000378:metabolism; D008175:Lung Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics*; D009928:Organ Specificity; D063150:Polycomb Repressive Complex 1; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000235:genetics*; D012097:Repressor Proteins; D015996:Survival Rate; D014407:Tumor Cells, Cultured; D025803:Tumor Suppressor Protein p14ARF; D016335:Zinc Fingers
C069077:BMI1 protein, human; D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009687:Nuclear Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D025803:Tumor Suppressor Protein p14ARF; D063150:Polycomb Repressive Complex 1