Co-expression of Fas (APO-1, CD95)/Fas ligand by BeWo and NJG choriocarcinoma cell lines

OBJECTIVE

Fas (CD95) is a transmembrane protein of the tumor necrosis factor receptor superfamily that induces apoptosis in susceptible cells on crosslinking by its ligand (FasL). The Fas loss of function and concurrent expression of its ligand (FasL) have been associated with malignant phenotype. In this study, we sought to investigate the hitherto undescribed expression of Fas and FasL on the immortalized human choriocarcinoma cell lines BeWo and NJG.

METHODS

Receptor and ligand expression was demonstrated using specific antibodies and multiple techniques including immunocytochemistry, confocal immunofluorescence microscopy, flow cytometry, immunoblots, and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Data from this study indicate that human choriocarcinoma cell subtypes co-express both Fas and FasL. A specific cytoplasmic and membranous pattern of immunoreactivity was noted that was further confirmed at mRNA transcripts by RT-PCR. In addition, we provide evidence using flow cytometry that the Fas receptors are downregulated. The mean fluorescence intensities for NJG and BeWo were 1.47 +/- 0.5 and 1.59 +/- 0.4, while that for Fas-positive Jurkat cells was 25.6 +/- 3.1.

CONCLUSIONS

To our knowledge, this is the first report on the identification and constitutive co-expression of Fas and FasL in BeWo and NJG choriocarcinoma cells. Choriocarcinoma cells evade immune attack by downregulating the Fas receptor and by killing lymphocytes through expression of FasL. Taken together, our investigations suggest that the Fas/FasL system may represent a mechanism by which malignant trophoblasts become resistant to apoptosis, escape immune surveillance, and metastasize.

Resistance to Fas-mediated cell death in BeWo and NJG choriocarcinoma cell lines: implications in immune privilege

OBJECTIVE

An immune privileged site occurs when the allogenic tissue grafts have the propensity for prolonged survival in the host tissue. In this context, the survival and proliferation of malignant trophoblasts in the gravid uterus are currently unclear. In a previous study, we documented that Fas and FasL are coexpressed in choriocarcinoma [Gynecol. Oncol. (2003)]. This study was conducted to examine the role of the Fas/FasL pathway in immune privilege of BeWo and NJG choriocarcinoma cells in culture.

METHODS

The ability of anti-Fas mAb (CH-11) to sensitize choriocarcinoma cell lines to Fas-mediated cytotoxicity was assessed by MTT assays. Coculture experiments with Fas-sensitive Jurkat cells were used to demonstrate functional FasL from choriocarcinoma. RT-PCR was used to assess the expression of cFLIP.

RESULTS

The mean cell viability of BeWo and NJG cells declined to about 58 and 63% compared to controls after 72 h of culture in the presence of anti-Fas mAb (CH-11) while the Fas-sensitive Jurkat cells showed viability of only 10%. This resistance to Fas-mediated apoptosis in choriocarcinoma cells is reversed in the presence of cycloheximide (0.5 micro g/ml) which further decreased the viability to 36 and 32%, respectively, at a dose of 300 ng/ml (P < 0.05). The observed resistance to Fas-mediated apoptosis therefore could be attributed to the short-lived endogenous inhibitor, cFLIP as demonstrated by the RT-PCR technique. In coculture experiments, FasL from choriocarcinoma cells induced apoptosis in the Fas-sensitive Jurkat cells, thereby indicating the capacity to evade immune attack.

CONCLUSIONS

Decreased sensitivity to Fas-mediated apoptosis and counterattacking the lymphocytes may impart immune privilege in these malignant trophoblasts for prolonged survival in the host.

Sonographic fetal weight estimation in a south-east Asian population

OBJECTIVES

To determine the optimal sonographic fetal weight estimation formula for a mixed south-east Asian population near term.

METHODS

Seventy-eight uncomplicated pregnancies were monitored between January 1996 and January 1997. Biparietal diameter, head circumference, abdominal circumference and femur length were measured and the following formulae were tested: Campbell, Shepherds and Hadlock. The estimated fetal weight was calculated by 12 different methods. The weight estimate was then projected forward to the time of delivery using the gestation-adjusted forward projection method. The weight estimation error was derived from the difference between the projected fetal weight and birth weight, and expressed as a percentage of birth weight.

RESULTS

The mean time interval from the time of ultrasound fetal weight estimation to delivery was 4.4 days. The birth weight ranged between 2,330 to 4,215 g. The best performing formula was Hadlock's formula using the head circumference, abdominal circumference and femur, with the perimeters calculated using the ellipse function. The standard deviation of error for this formula was 8.66%.

CONCLUSION

Even though the Hadlock formula was originally derived from an American population, it was equally useful in south-east Asian population.

Threatened abortion: prediction of viability based on signs and symptoms

OBJECTIVE

To examine the relationship between signs and symptoms associated with threatened abortion and viability of the pregnancy.

DESIGN

A prospective observational study

SETTING

A university teaching hospital

PARTICIPANTS

One thousand consecutive women presenting with a threatened abortion.

INTERVENTION

A structured history and an examination were performed as initial clinical assessment. These were followed by transvaginal sonography to determine the status of the pregnancy.

MAIN OUTCOMES

The relationship between individual signs and symptoms and the status of the pregnancy was determined. Logistic regression was performed to determine which signs or symptoms were independent predictors of spontaneous abortion.

RESULTS

A history of having passed a tissue mass, the presence of products of conception in the vagina and an open cervix were the only sign or symptom associated with a greater than 90% chance that the pregnancy was non-viable. Logistic regression of signs and symptoms at presentation indicated that maternal age greater than 35 years, a history of passing clots vaginally, vaginal bleeding similar to normal menstruation, increasing vaginal bleeding and discrepancy of 4 or more weeks between the uterine size on examination and that which would have been expected by menstrual dates were significant predictors of nonviable pregnancy. A history of vomiting was predictive of a viable pregnancy.

CONCLUSION

The clinical assessment of threatened abortion is unreliable in most cases and should be superseded by ready access to sonographic assessment.

Lipid peroxidation in cord blood at birth: the effect of labour

OBJECTIVE

To determine the effect of labour on free oxygen radical activity in the fetus, as reflected by lipid peroxide levels in umbilical cord arterial blood.

DESIGN

Prospective, observational study.

SETTING

Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong.

METHODS

Umbilical cord arterial and venous blood samples were collected from singleton term infants delivered by elective caesarean section. Base excess, PO2, pCO2 and pH were measured in both samples and compared to identify double venous samples. Cord arterial acid-base balance and concentrations of organic hydroperoxides and malondialdehyde were compared with those obtained from normal vaginal deliveries.

RESULTS

Cord arterial blood samples, obtained from cases of uncomplicated labour followed by spontaneous vaginal delivery, had significantly higher lipid peroxide concentrations than those delivered following elective caesarean section. This was most marked for malondialdehyde with a median value increased by 105%, whilst organic hydroperoxide was increased by only 27%. Of the acid-base parameters, base excess was increased by 78%, with only minimal changes in pH, pCO2 and PO2. These differences remained highly significant after including other pregnancy characteristics in multivariate analysis.

CONCLUSION

The findings indicate that high levels of free oxygen radical activity in the fetus are a function of the labour process, as are changes in acid-base balance.

Intrauterine growth retardation

IUGR puts the fetus at risk of stillbirth, perinatal morbidity and neonatal handicap, yet most instances of IUGR are not recognized. Progress has been made in recent years to monitor the high-risk fetus with intensive biometric and biophysical tests and to determine the appropriate time for intervention. These methods of surveillance are ineffective and inappropriate for population screening, and the main problem remains how to identify the at-risk fetus. Improvement of current performance requires the establishment of appropriate standards by which intrauterine growth can be assessed, and their introduction as part of well-organized screening programmes. We describe a computerized method of predicting the optimal weight for each pregnancy, which is individually adjusted for non-pathological variables such as maternal height, booking weight, ethnic group and parity. The optimal birthweight determines the expected slope or velocity of fetal weight gain. This individualized prediction improves the distinction between constitutional and pathological smallness. Furthermore, preterm weights are measured against a fetal weight norm rather than a birthweight standard that is derived from non-physiological preterm deliveries. The customized growth chart allows screening for growth retardation by determining the growth velocity through serial measurement and plotting of fundal height, backed up as necessary by ultrasound estimation of fetal weight and referral for more intensive surveillance as indicated.