The bone morphogenetic protein pathway is inactivated in the majority of sporadic colorectal cancers.
OBJECTIVE
The finding of bone morphogenetic protein (BMP) receptor 1a mutations in juvenile polyposis suggests that BMPs are important in colorectal cancer (CRC). We investigated the BMP pathway in sporadic CRC.


METHODS
We investigated BMP receptor (BMPR) expression using immunoblotting and sequenced BMPR2 in CRC cell lines. We assessed the expression of BMPRs, SMAD4, and pSMAD1/5/8 in 72 sporadic CRCs using a tissue microarray and immunohistochemistry. We assessed the effect of reintroduction of wild-type BMPR2 on BMP pathway activity and the effect of wild-type or mutated BMPR2 3' untranslated region (UTR) sequences on protein expression by attachment to pCMV-Luc.


RESULTS
BMPR2 and SMAD4 protein expression is abrogated in microsatellite unstable (MSI) and microsatellite stable (MSS) cell lines, respectively. BMPR2 3'UTR is mutated in all MSI and in none of the MSS cell lines. Mutant BMPR2 3'UTR sequences reduced luciferase expression 10-fold compared with wild-type BMPR2 3'UTR. BMPR2 expression is impaired more frequently in MSI CRCs than MSS (85% vs 29%; P < .0001) and shows a mutually exclusive pattern of impaired expression compared with SMAD4. Nine of 11 MSI cancers with impaired expression of BMPR2 have microsatellite mutations. The BMP pathway is inactivated, as judged by nuclear pSMAD1/5/8 expression, in 70% of CRCs, and this correlates with BMPR and SMAD4 loss.


CONCLUSIONS
Our data suggest that the BMP pathway is inactivated in the majority of sporadic CRCs. In MSI CRC this is associated predominantly with impaired BMPR2 expression and in MSS CRC with impaired SMAD4 expression.
Kodach
Liudmila L
LL
Department of Gastroenterology, Leiden University Medical Center, Leiden, The Netherlands.
Wiercinska
Eliza
E
de Miranda
Noel F C C
NF
Bleuming
Sylvia A
SA
Musler
Alex R
AR
Peppelenbosch
Maikel P
MP
Dekker
Evelien
E
van den Brink
Gijs R
GR
van Noesel
Carel J M
CJ
Morreau
Hans
H
Hommes
Daniel W
DW
Ten Dijke
Peter
P
Offerhaus
G Johan A
GJ
Hardwick
James C H
JC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000235:genetics; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis / Q000235:genetics*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D053842:Microsatellite Instability; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D009154:Mutation; D012334:RNA, Neoplasm / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051901:Smad4 Protein / Q000096:biosynthesis / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics*
C525718:BMP2 protein, human; D014408:Biomarkers, Tumor; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D012334:RNA, Neoplasm; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta