Transcriptional analysis of novel hormone receptors PGRMC1 and PGRMC2 as potential biomarkers of breast adenocarcinoma staging.
BACKGROUND
The expression of progesterone receptor membrane component 1 (PGRMC1) in breast cancer has generated interest in this recently discovered protein because of its role in tumorigenesis. However, correlations between patient age, PGRMC1 gene expression, breast cancer morphology, and breast cancer stage have not been adequately studied. Furthermore, very little is known about possible roles for other PGRMC isoforms in breast cancer, like PGRMC2. Thus, we examined the expression of PGRMC1 and PGRMC2 mRNA by relative quantitative PCR (RelqPCR) and determined whether transcript levels correlate with age, breast cancer staging, estrogen receptor alpha (ERα) status, and other morphometric features routinely used during the pathological examination of breast ductal adenocarcinomas.


METHODS
Twenty-eight frozen or paraffin embedded breast cancer samples (ductal carcinoma in situ and stages I thru IV invasive ductal adenocarcinoma) and 10 control benign breast tissue samples were randomly selected and interrogated by RelqPCR to determine PGRMC1, 2, and ERα mRNA transcript levels. To control for slight variations in sample preparation, receptor transcript was normalized to the housekeeping gene phosphoglycerate kinase 1 (PGK1). Descriptive statistics and ANOVA of multiparametric datasets were used to correlate transcript levels with pathological staging parameters.


RESULTS
PGRMC1 mRNA levels decreased significantly with patient age (Pearson's correlation -0.369; P=0.035), whereas PGRMC2 levels did not. Although the mean relative expression of PGRMC1 significantly decreased in stage II breast cancer compared with controls (P=0.050), it was no longer significant when age was considered a covariance (P=0.371). On the other hand, PGRMC2 mRNA transcript was significantly decreased in stage II breast cancer when compared to stage III cancer (P=0.028) in a manner independent of age (corrected model Bonferroni pair wise comparison, P=0.036). Furthermore, PGRMC2 levels positively correlated with ERα mRNA transcripts in patients with ER positive tumors (Pearson's correlation 0.503, P=0.096).


CONCLUSIONS
Decreases in PGRMC1 mRNA are partially explained by increasing patient age. On the other hand, compared to stage III, PCRMC2 mRNA was significantly decreased in stage II adenocarcinoma of the breast in an age-independent manner. Additionally, PGRMC2 mRNA levels displayed a positive correlation with ERα transcripts. Thus, in addition to morphometric pathologic staging criteria, measurements of PGRMC2 mRNA may be useful for distinguishing low stage tumors from higher stages that require more aggressive clinical management, and may be a useful test when tumor ER IHC results are equivocal.
Causey
Marlin Wayne
MW
Department of General Surgery, Madigan Army Medical Center, Fort Lewis, Tacoma, Washington 98431, USA. mwcausey@msn.com
Huston
Laurel J
LJ
Harold
Dawn M
DM
Charaba
Cameron J
CJ
Ippolito
Danielle L
DL
Hoffer
Zachary S
ZS
Brown
Tommy A
TA
Stallings
Jonathan D
JD
D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology*; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology*; D002278:Carcinoma in Situ / Q000235:genetics / Q000473:pathology; D044584:Carcinoma, Ductal / Q000235:genetics / Q000473:pathology; D047628:Estrogen Receptor alpha / Q000235:genetics; D005260:Female; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism; D011980:Receptors, Progesterone / Q000235:genetics*; D014158:Transcription, Genetic / Q000502:physiology
D014408:Biomarkers, Tumor; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D008565:Membrane Proteins; C115296:PGRMC1 protein, human; C115297:PGRMC2 protein, human; D012333:RNA, Messenger; D011980:Receptors, Progesterone