Genetic integrity of transforming growth factor beta (TGF-beta) receptors in cervical carcinoma cell lines: loss of growth sensitivity but conserved transcriptional response to TGF-beta.
Transforming growth factor beta (TGF-beta) exerts an inhibitory effect on the growth of most epithelial cell types, and the loss of responsiveness to this growth inhibition has been implicated in the development of a variety of human cancers. The genetic alteration of TGF-beta receptors is known to play a critical role in this escape from growth regulation. We asked whether there is a correlation between TGF-beta sensitivity and the genetic status of TGF-beta type I and type II receptors (RI and RII, respectively) in human cervical carcinoma cell lines. Among 8 cell lines examined, 3 (ME-180, C-33A and HeLaS3) showed resistance to TGF-beta and 3 (SiHa, CaSki and HeLa229) showed minimal response to the growth inhibitory effect of TGF-beta; the other cell lines (HeLa and HT-3) were sensitive. Northern blot analysis revealed that the RII mRNA was not expressed in 2 TGF-beta-resistant cell lines (ME-180 and C-33A) but was expressed in the other cell lines. Southern blot analysis of RI and RII revealed a homozygous deletion of the entire TGF-beta RII gene in the cell line ME-180. We then asked whether the other TGF-beta-resistant or refractory cell lines had microsatellite instability and/or poly-adenine tract mutations of RII. We also checked for point mutations in the individual exons of the entire RII using polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP). Although C-33A exhibited poly-adenine microsatellite instability, its RII gene showed no signs of mutation. The molecular integrity of the TGF-beta, receptors in all cell lines, except ME-180 and C-33A, could be confirmed by examining the distinct transcriptional induction of plasminogen activator inhibitor-1 (PAI-1), p21(WAF1/CIP1) and, in some cases, the accompanying downregulation of c-myc in response to TGF-beta. Our observations, taken together, indicate that inactivation of the RII contributes to the resistance to TGF-beta of some cervical carcinoma cell lines. Loss of or attenuated sensitivity to TGF-beta growth inhibition in other cells may be attributed to the disruption of distal components in the TGF-beta signal pathway, but not to the receptor system.
Kang
S H
SH
Cancer Research Center, Seoul National University College of Medicine, Korea.
Won
K
K
Chung
H W
HW
Jong
H S
HS
Song
Y S
YS
Kim
S J
SJ
Bang
Y J
YJ
Kim
N K
NK
D015139:Blotting, Southern; D002455:Cell Division / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D006367:HeLa Cells / Q000187:drug effects; D006801:Humans; D018895:Microsatellite Repeats / Q000235:genetics; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D019680:Trinucleotide Repeat Expansion / Q000235:genetics; D014407:Tumor Cells, Cultured / Q000187:drug effects; D002583:Uterine Cervical Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004273:DNA, Neoplasm; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta