Abstract
At present, there are no markers that accurately predict the developmental competence of human IVF embryos. Clinicians conducting IVF rely on unreliable methods, such as morphology, in order to select embryos. As such, it is often the case that more than one embryo will be transferred to the uterus so as to maximize the likelihood of a pregnancy. However, this strategy poses an increased risk of multiple pregnancy, which represents a health risk for both mother and child.
Previously, when multiple embryos were transferred, it has been impossible to ascertain which embryo developed into a successful pregnancy and, as such, identifying criteria for viable embryos has been problematic. In a recent study, a novel strategy involving DNA fingerprinting was investigated for its competence to predict which blastocysts would result in successful births.
“…utilizing a combination of blastocyst biopsy, DNA fingerprinting and microarray analysis to identify viable blastocysts…”
David Cram, coauthor and senior research scientist at the Monash Immunology and Stem Cell Laboratories at Monash University, Australia, remarked, “DNA fingerprinting is the ultimate form of biological identification, but until now it has not been used to identify the embryonic origin of resultant babies born following embryo transfer; nor has it been used for gene expression studies.” He added, “We have developed a novel strategy of utilizing a combination of blastocyst biopsy, DNA fingerprinting and microarray analysis to identify viable blastocysts among the cohorts transferred to patients.”
A total of 48 women undergoing IVF were recruited for the study. Using a noncontact laser, the researchers took biopsies of the blastocysts, prior to transfer, removing 8–20 trophectoderm cells for molecular analysis. Using microarrays, biopsy samples were amplified and gene expression was evaluated.
Each woman in the study had at least one of their blastocysts transferred to their womb, with a total of 25 of the 48 women becoming pregnant and 38 babies being born. After birth, the researchers took blood samples from the umbilical cord or swabs of cheek cells from the babies and used DNA fingerprinting to match these samples with the DNA obtained from the blastocyst biopsies.
By conducting comparative analysis of cDNA from pooled ‘viable’ and ‘nonviable’ trophectoderm cells, the researchers were able to identify more than 7000 transcripts that were expressed exclusively in the viable transcripts. The most significant transcripts were involved in cell adhesion and cell communication – key processes associated with implantation – as noted by the researchers in the journal, Human Reproduction.
Coauthor Gayle Jones commented, “The ability to use objective, measurable criteria rather than subjective observations, such as morphology, should improve the predictive value and provide sufficient confidence for clinicians to shift toward single-embryo transfers for all patients without a concomitant drop in pregnancy rates. This would effectively reduce multiple pregnancies, which is a priority in the field of assisted reproductive medicine at present.”
The study authors recognize that, while the methods used for this study are yet not ready for clinical use, potentially, these methods could be used to test different treatments of embryos without the need to recruit large numbers of women for clinical trials. In addition, DNA fingerprinting could be exploited to supplement current methods of selecting embryos for implantation.
Dr Allan Pacey, senior lecturer at the University of Sheffield, UK, and honorary secretary of the British Fertility Society, UK, commented, “As we move increasingly toward elective single-embryo transfer for as many patients as possible, it will become increasingly important to be able to select which embryos are the most likely to lead to pregnancies.”
“The ability to select the single most viable embryo from within a cohort available for transfer will revolutionize the practice of IVF…”
“Major improvements in IVF practice in the last decade have seen the introduction of better laboratory techniques that allow complete preimplantation development to the blastocyst stage in vitro. One of the major stumbling blocks to worldwide acceptance of a single-embryo transfer policy is the lack of highly predictive criteria to select the single most viable embryo within a cohort,” explained Jones. “The ability to select the single most viable embryo from within a cohort available for transfer will revolutionize the practice of IVF, not only improving pregnancy rates but eliminating multiple pregnancies and the attendant complications,” she enthused.
Source: Jones GM, Cram DS, Song B, Kokkali G, Pantos K, Trounson AO: Novel strategy with potential to identify developmentally competent IVF blastocysts. Hum. Reprod. (2008) (Epub ahead of print).
in brief…
Kenfield SA, Stampfer MJ, Rosner BA, Colditz GA: JAMA 29(17), 2037–2047 (2008).
A recent study aimed to identify the association between cigarette smoking and smoking cessation on total and cause-specific mortality in women. The researchers conducted an observational study of 104,519 women in the Nurses Health Study, conducting follow-up between 1980 and 2004. Overall, a total of 12,483 deaths occurred; 4485 (35.9%) were among nonsmokers, 3602 (28.9%) were among current smokers and 4396 were among past smokers. The results demonstrated that current smokers had an increased risk of total mortality and all major cause-specific mortality, compared with nonsmokers. Approximately 64% of deaths among current smokers and 28% of deaths among former smokers were attributable to smoking. The researchers concluded that the increased risk of vascular mortality caused by smoking in women can be eliminated rapidly upon cessation and within 20 years for lung diseases. In addition, postponing the age of smoking initiation reduces the risk of smoking-related cancer deaths, but has little effect on other cause-specific mortality.
Martín M, Rodríguez-Lescure A, Ruiz A et al.: J. Natl Cancer Inst. 100(11), 805–814 (2008).
Following breast cancer surgery, researchers randomly assigned women with lymph node-positive disease to treatment with fluorouracil, epirubicin and cyclophosphamide (FEC) or with FEC followed by weekly paclitaxel (FEC-P). Kaplan–Meier analysis was used to assess the primary end point of the study, 5-year disease-free survival (DFS). Among the 1246 patients who were eligible for the trial, estimated rates of DFS at 5 years in the FEC-P and FEC arms were 78.5 and 72.1, repectively. Compared with FEC treatment, FEC-P treatment was found to be associated with a 23% reduction in the risk of relapse as well as a 22% reduction in the risk of death. In the 928 patients for whom tumor samples were centrally analyzed, type of chemotherapy, number of involved axillary lymph nodes and HER2 status were all associated with DFS. The researchers conclude that, among patients with operable breast cancer, treatment with FEC-P significantly reduced the risk of relapse compared with FEC as adjuvant therapy.
German study provides further support for associations between HRT and breast cancer
In a large population-based, case–control study, which investigated 3464 breast cancer cases aged 50–74 years at diagnosis as well as 6657 population-based and menopausal frequency-matched controls, researchers investigated the effects of HRT by type, regimen, timing and progestagenic constituent on overall postmenopausal breast cancer risk.
Results of the study demonstrated that the risk of invasive breast cancer was significantly elevated in current users. In addition, the risk of invasive breast cancer related to the use of HRT was found to differ by histological type; risk of lobular and tubular cancer were more than twofold higher compared with the risk for lobular cancer.
“HRT also appears to have a different influence on different types of breast cancer,” Wilhelm Braendle of Hamburg–Eppendorf University Hospitals, Germany, one of the study's authors, noted. “The risk of developing one of the less common lobular or tubular breast cancers increases twice as much under HRT as the risk of the common type of ductal carcinoma, which constitutes 40–75% of all malignant tumors of the breast.”
The study also demonstrated that following 5 years cessation of HRT use, there was no statistically significant increase in breast cancer risk, a finding that was demonstrated for all histological types of breast cancer.
Analyses relating to progestagenic content by regimen demonstrated that continuously administered norethisterone conferred a significantly higher risk of breast cancer compared with levonorgestrel-derived progestagens. However, the researchers note that this finding may be explained by dosage, rather than type of progestagen.
‘…the risks associated with menopausal HRT may differ with the type and regimen of HRT used as well as the histological type of breast cancer, and that the progestagenic component may also play a role, depending on the effective dose.’
“It has often been argued that the results of the US [Women's Health Initiative] study could not be applied to Germany where prescription practices are completely different. Therefore, we captured the various hormone preparations, especially the various progestins, very precisely. We have obtained similar results as the US researchers,” coauthor, Jenny Chang-Claude notes. “With our new data, we provide physicians in Germany with solid information that will help them to advise their patients about the benefits and risks of HRT.”
The researchers conclude that their data suggest that the risks associated with menopausal HRT may differ with the type and regimen of HRT used as well as the histological type of breast cancer, and that the progestagenic component may also play a role, depending on the effective dose.
Source: Flesch-Janys D, Slanger T, Mutschelknauss E et al.: Risk of different histological types of postmenopausal breast cancer by type and regimen of menopausal hormone therapy. Int. J. Cancer (2008) (Epub ahead of print).
Study suggests a high-risk population among breast cancer patients for development of brain metastases
In a retrospective study analyzing risk factors influencing time to development of brain metastases, researchers from the University of Vienna, Austria, aimed to identify a high-risk population among breast cancer patients. A total of 174 breast cancer patients who were diagnosed with invasive breast cancer at a median age of 51 years and later developed brain metastasis were included in the study.
Previous research has found that several factors, such as hormone receptor status, young age at time of diagnosis and HER2/neu overexpression, are risk factors for the development of brain metastases. The investigators conducted statistical analysis including the aforementioned factors as well as tumor grading, tumor stage, adjuvant systemic treatment, palliative systemic treatment, metastatic sites (if brain metastases were not the first site of recurrence) and immunotherapy with trastuzumab.
The research, published in the journal Breast demonstrated that the median time to cerebral progression after primary diagnosis was 54 months for stage I disease, 39 months for stage II disease, 22 months for stage III disease and 13 months for stage IV disease. Upon multivariate analysis, the results demonstrated that high tumor grade, under 35 years of age, and treatment with HER2 monoclonal antibody therapy were all factors associated with a shortened time to development of brain lesions.
The authors suggest that the latter finding may reflect the fact that patients who are treated with HER2 monoclonal antibody have aggressive disease and antibody therapy is unable to cross the blood–brain barrier. Recent evidence has suggested that whole brain radiotherapy may compromise the blood–brain barrier, allowing subsequent systemic treatment with HER2 monoclonal antibodies to be more effective.
Sabine Fromm and colleagues suggest that radiological screening should be conducted in these patients as early as possible “before irreversible neurological damage occurs.” Moreover, they argue that these patients “might even benefit from prophylactic whole brain radiotherapy, similar to small cell lung cancer or adenocarcinoma of the lung.”
The study authors conclude that further research into preventative measures is warranted in order to identify a high-risk population among breast cancer patients allowing the development of screening programs to facilitate early detection, noting, “Cerebral metastases are a big problem for the treating oncologist and up to now no truly effective systemic treatment options exist.”
Source: Fromm S, Bartsch R, Rudas M: Factors influencing the time to development of brain metastases in breast cancer. Breast (2008) (Epub ahead of print).
Use of NSAIDs may reduce the incidence of ovarian cancer in high-risk women
In a recent population-based, case–control study in Wisconsin and Massachusetts, USA, researchers investigated the association between the use of NSAIDs with parity and oral contraceptive use. A total of 487 invasive ovarian cancer cases and 2653 control women aged 20–74 years were included in the analysis and information was obtained during telephone interviews.
After adjusting for factors such as age, state of residence and other covariates, the researchers found that, overall, women who had used any type of NSAIDs were 30% less likely to have ovarian cancer than nonusers. According to the study, published in the British Journal of Cancer, taking NSAIDs could potentially reduce women's risk for developing ovarian cancer.
“NSAIDs may confer greater protection from ovarian cancer in women with higher background levels of inflammation…”
“Both pregnancy and use of oral contraceptives are associated with decreased ovarian cancer risk through their inhibitory effects on ovulation, such as incessant ovulation,” the researchers explain.
The results demonstrate that women who had never used oral contraceptives were 42% less likely to have ovarian cancer if they used NSAIDs and nulliparous women were 53% less likely, compared with nonusers. By contrast, there was no benefit for parous women or women who had used oral contraceptives.
The authors conclude that “NSAIDs may confer greater protection from ovarian cancer in women with higher background levels of inflammation such as those from incessant ovulation.”
Source: Wernli KJ, Newcomb PA, Hampton JM, Trentham-Dietz A, Egan KM: Inverse association of NSAID use and ovarian cancer in relation to oral contraceptive use and parity. Br. J. Cancer 98(11), 1781–1783 (2008).