Trophoblastic cells expressing human chorionic gonadotropin genes in peripheral blood of patients with trophoblastic disease

Differential expression of SALL4 in CTCs derived from hydatidiform moles and gestational trophoblastic neoplasms

PROBLEM

To investigate EMT phenotype and SALL4 expression of circulating tumour cells (CTCs) in patients with gestational trophoblastic neoplasm (GTN).

METHOD OF STUDY

CanPatrol CTC detection system in combination with SALL4 RNA in situ hybridization was used to investigate the profile of CTCs in different types of gestational trophoblastic disease (GTD). Circulating CTCs were phenotyped and annotated with SALL4 expression in 41 GTD patients, including 12 HM and 29 GTN, as well as 22 pregnant volunteers.

RESULTS

A positive correlation between the number of CTC and serum β-hCG concentration was found among the GTN patients. The number of E/M-CTC was positively correlated with serum β-hCG, while M-CTC was positively correlated with prognostic score. Comparison among malignant GTD, benign GTD and healthy pregnant women revealed a significant difference in the number of total CTC, E/M-CTC, and M-CTC but not in E-CTC. ROC analysis was conducted to evaluate the performance of CTC phenotypes in distinguishing GTD patients from healthy pregnant women yielding an AUC as 0.826. Youden's index was maximal at the cutoff value of 8.5/4 mL with sensitivity and specificity at 53.66% and 100%, respectively. SALL4 expression was evaluated in GTD patients with CTC count greater than cutoff value. SALL4 high expressing CTCs (>2 signal dots) were detected in 66.67% (10/15) of malignant GTD patients but not in benign patients (0/5).

CONCLUSION

Differential expression of SALL4 was seen in CTCs derived from hydatidiform moles and GTN. CTC profiling may be developed as an adjunct marker to diagnose GTN.

PLAC1 mRNA in maternal blood correlates with Doppler waveform in uterine arteries in normal pregnancies at the second and third trimester

Doppler analysis of the uterine arteries is currently used for pre-eclampsia (PE) screening. PLAC1 is a trophoblast-specific gene, and it is known that in normal pregnancies, trophoblastic cells are released into the maternal circulation, where specific trophoblastic mRNA can be detected. In PE, as in women who eventually develop PE, an abnormal passage of fetal and placental cells is also present. In this study, we aimed to verify whether, in normal pregnancies, Doppler waveform of the uterine arteries correlates with PLAC1 mRNA concentrations. Thirteen cases of normal pregnancies at 37 weeks' gestation (23-41) were enrolled in the study. PLAC1 mRNA was extracted from 2 mL of blood by ABI PRISM 6100 nucleic acid Prep Station (Applied Biosystems, Foster City, CA) and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed by a PE 5700 Sequence detection system. Bulk RNA from normal placental tissue was used as the reference curve, and the amount of PLAC1 mRNA in the study samples was then expressed as the "relative amount" of weight of placental tissue (ng/mL). The uterine arterial mean resistance index (RI) and presence/absence of a dicrote waveform were calculated by using a 5 MHz transabdominal probe (Tecnos, ESAOTE) at the uterine cervico-corporal junction. Doppler measurement was performed on the same day as blood collection. The median of the means of uterine arterial RI was 0.52 (0.39-0.68). RI of uterine arteries and PLAC1 mRNA were significantly correlated in a log-linear regression (R(2) = 0.483, P = 0.024). Our data support that in normal pregnancy, the passage of trophoblast material into the maternal circulation is correlated with the quantitative measurement of uterine hemodynamics.

Rapid Clearance of mRNA for PLAC1 Gene in Maternal Blood after Delivery

OBJECTIVE

To evaluate (1) whether the presence of mRNA for the specific trophoblast gene PLAC1 in maternal whole blood is pregnancy-specific, and (2) whether delivery would result in the clearance of mRNA from maternal blood.

METHODS

Sixteen pregnant women at term (41 completed weeks' gestation) were enrolled in the study. Blood samples were obtained before the onset of labor and 24 h after delivery. Eight healthy donors (3 males and 5 non-pregnant women) were used as controls. Total RNA was extracted by means of ABI Prism 6100. A quantitative evaluation was obtained by means of real-time PCR. Wilcoxon test was used to evaluate differences between time intervals.

RESULTS

Median concentrations of PLAC1 mRNA relative to the standardization curve (see below) were 44 (2.9-675) ng/ml and 0.48 (0.05-10.7) ng/ml respectively for pre- and post-delivery samples (p value <0.001). Male and non-pregnant female controls did not show any signal of cDNA amplification.

CONCLUSION

mRNA transcripts from a placenta-expressed specific gene are detectable in maternal blood and rapidly disappear after delivery. Such an mRNA provides a gender-independent marker for non-invasive prenatal gene expression profiling, and can open new perspectives to monitor those conditions associated to trophoblast damage as well as preeclampsia.

Human chorionic gonadotropin in cancer

Human chorionic gonadotropin (hCG) is mainly used for detection and monitoring of pregnancy and pregnancy-related disorders but it is also an extremely sensitive and specific marker for trophoblastic tumors of placental and germ cell origin. Thus treatment of relapsing choriocarcinomas and testicular germ cell tumors is often initiated on the basis of rising hCG levels even in the absence of clinical or histological evidence of a relapse. While these tumors mostly produce the intact heterodimeric hormone consisting of an alpha (hCGalpha), and a beta subunit (hCGbeta), many nontrophoblastic tumors produce only hCGbeta This is usually a sign of aggressive disease and elevated serum levels of hCGbeta are strongly associated with poor prognosis. Elevated serum levels are observed in 45-60% of patients with biliary and pancreatic cancer and in 10-30% of most other cancers. Methods that detect hCG and hCGbeta together are mainly used for measurement of hCG-like immunoreactivity in serum. However, the reference range for hCG is 5-8 fold higher than that for hCGbeta and thus moderately elevated levels can be identified only with a specific and sensitive hCGbeta assay.

Circulating trophoblast in maternal blood

This review describes the status of circulating trophoblast, but is considered in the perspective that only a specific subset of trophoblast cells circulates in the maternal blood. The consequences for isolation, identification and clinical potential are described.