P–433 Pregnancy and livebirth after fertility preservation in cancer patients

Study question

What do we know about pregnancy and livebirth after IVF- fertility preservation treatment in women with cancer?

Summary answer

Most women conceived spontaneously (60%) and more than 50% of those who returned to use their cryopreserved reproductive material have delivered at least one child.

What is known already

Diminishing ovarian reserve and declining future reproductive potential are important issues in cancer survivors after anti-cancer treatment exposure. Publications on pregnancy and livebirth after fertility preservation in women with cancer are sparse. Studies report most cancer patient who underwent fertility preservation do not come back and use their frozen reproductive material. The purpose of this study was to investigate the fertility preservation outcome among cancer survivors.

Study design, size, duration

A retrospective cohort study was conducted at a single academic fertility center from including 336 cancer patients who underwent IVF-fertility preservation from January 2009 to June 2020.

Participants/materials, setting, methods

We included all women with cancer aged ≤40 years old who were referred for fertility preservation treatment prior to chemotherapy.

Primary outcome: Number of pregnancies and livebirths after spontaneous conception and/or using their stored frozen material.

Secondary outcomes: We also evaluated the utilization rate of the stored reproductive material and mortality rate among those with follow up data.

Main results and the role of chance

Of 336 patients who underwent IVF-fertility preservation, 214 (63.69%) elected oocyte cryopreservation, 86 (25.5%) underwent both embryo and oocyte cryopreservation and 36 (10.7`%) underwent embryo cryopreservation. Follow up data were available in 198 (58.9%) patients with a mean follow up of 3.2 years. Of 198, 16 (8%) patients died, 40 (20%) became pregnant. Of those pregnant patients, 24 (60%) became spontaneously pregnant and 16 (40%) became pregnant after frozen oocyte or frozen embryo treatment cycles. Almost a quarter (72.5%) of the pregnancies resulted in livebirths. In total, only 23 (7%) patients had returned for frozen oocyte or frozen embryo treatment cycle, of which 16 (70%) achieved a pregnancy and 10 (63%) achieved at least one live birth. Of 142 patients who were still alive at follow up but did not get pregnant, 51 (39%) were in remission from their cancer but had not chosen to use their stored reproductive material; 44 (31%) were still on anti-cancer treatment and had not started trying yet; 13 (9%) were suffering from the end-stage cancer disease; and 7 (5%) had used their stored reproductive material but failed and stopped trying to get pregnant.

Limitations, reasons for caution

The main limitation was the retrospective cohort study design which could introduce unidentified selection biases.

Wider implications of the findings: Of women who underwent IVF-fertility preservation for cancer, most did not come back for treatment for a variety of reasons. Of those who became pregnant, 60% conceived spontaneously. Of those who used their cryopreserved reproductive material, 63% delivered at least one child.

Trial registration number

2021/6935

P–325 The impact of letrozole on endometrial thickness in IVF cycles

Study question

Does daily administration of letrozole during IVF stimulation affect endometrial thickness ?

Summary answer

Patients treated with letrozole during fresh IVF cycles had a thinner endometrium on the day of trigger compared to patients who did not receive letrozole.

What is known already

Letrozole supplementation is commonly used during fertility preservation for breast cancer patients to reduce peak estrogen levels with no adverse effects on embryo outcomes. Studies in poor responders have found that letrozole use resulted in a shorter duration of stimulation and a lower total dose of gonadotropin, with no detrimental effect on IVF outcomes. In normal responders, studies have shown an increase in blastocysts obtained, but have not yet shown an increase in clinical pregnancy rates. There is concern that when a fresh embryo transfer is planned letrozole use may negatively affect endometrial thickness and subsequently diminish pregnancy rates.

Study design, size, duration

In a retrospective cohort study between January 2009 and June 2019 at a single academic fertility center, we compared the endometrial thickness in 97 cancer patients who underwent IVF-fertility preservation with daily letrozole use to 158 cancer patients who underwent IVF-fertility preservation without letrozole.

Participants/materials, setting, methods

All women diagnosed with cancer were referred for fertility preservation prior to gonadotoxic treatment exposure and were less than 40 years old at the time of oocyte retrieval. All patients who received letrozole started on day one of stimulation and continued until the day of oocyte retrieval. The primary outcome was endometrial thickness on the day of trigger. The secondary outcomes were number of oocytes retrieved, number of MII retrieved, and maximal estradiol level.

Main results and the role of chance

During the study period, 336 cancer patients underwent fertility preservation. Eighty-one patients were excluded; 50 because they had an intrauterine device or were on long term oral contraceptives and 31 because endometrial thickness was not documented. Of the remaining 255 patients, 86 had breast cancer, 95 had a hematological cancer and 74 had various other cancers. Ninety-seven cancer patients treated with letrozole were compared to 158 cancer patients who did not receive letrozole. Patients who received letrozole were significantly older (34 vs 28yrs, P < 0.0001). There were no significant differences in baseline characteristics such as BMI, AFC nor in the total duration for stimulation. Endometrial thickness on the day of trigger was significantly less in letrozole treated patients (8 vs 9mm, P < 0.003). There were no significant differences in total number of oocytes retrieved (12.5 vs 11, P = 0.126) nor in the number of mature oocytes (8 vs 8, P = 0.312). Patients in the letrozole group received a higher total gonadotropin dose (2680IU vs 1980IU, P = 0.016). The maximum estradiol level was significantly lower in patients treated with letrozole (1068 vs 3838ml/dl, P = <0.0001). A regression analysis showed that using letrozole during stimulation decreased the endometrial thickness by 0.81mm (CI –1.37 to –0.253, P = 0.005).

Limitations, reasons for caution

The retrospective nature of this study could have introduced selection and misinformation bias. We report on cancer patients where all oocytes or embryos were vitrified. Without fresh embryo transfer data, it is unclear if a thinner endometrium due to letrozole will effect the implantation or pregnancy rate.

Wider implications of the findings: As the use of letrozole expands beyond cancer patients and poor responders, it is important to understand the impact on the endometrium. This study shows that letrozole reduces endometrial thickness. However, the effect on endometrial function remains unknown. Further study is needed before letrozole can be used with fresh transfers.

Trial registration number

2020–6370

Changes in the expression of cardiac genes responsive to thyroid hormones in the chickens with cold-induced pulmonary hypertension

Cold stress is an environmental cause of pulmonary hypertension syndrome (PHS) in broiler chickens. This factor could increase the rate of metabolic activity via thyroid hormones (T3 and T4). To evaluate the effect of these hormones on the heart, the plasma concentration of T3, T4, and the gene expression of their receptors (THRα and THRβ) and many contractile proteins (ACTC1, MHCα, MHCβ, RYR2, SERCA2, THRα, THRβ, and troponin I) were measured in the right ventricle in 2 periods of age (21 and 35 d). Plasma T3 concentration was significantly higher in the PHS group of chickens than in the control one at 21 and 35 d while plasma T4 did not change. The relative expression of MHCα, RYR2, SERCA2, and THRα genes in the right ventricle tissues was only higher in PHS group of broilers than control group at 21 d (P < 0.05) whereas the expression of ACTC1, MHCβ, and troponin I did not differ at 2 periods of age. The positive correlations between MHCα, RYR2, SERCA2, and T3, THRα were confirmed. The expression of THRβ gene was only higher in PHS group of broilers than control at 35 d (P < 0.05). The data determined that cold stress could increase thyroid hormones and the gene expression of their receptor (THRα) in the pick of chicken growth (21 d) that they themselves elevates the expression of many genes related to contractile elements (MHCα, RYR2, and SERCA2), leading to adaptive right ventricle hypertrophy.

Tumour regression induced by co-administration of MIP-3α and CpG in an experimental model of colon carcinoma

CCL20/macrophage inflammatory protein-3α (MIP-3α) represents one of the potent chemoattractive proteins for dendritic cells (DCs). Herein, we investigated whether in vivo genetic modification of tumour cells aimed at intratumoural production of MIP-3α might lead to accumulation of DCs in tumour tissue. Mice injected with CT26, received recombinant adenovirus (Ad) vectors (AdMIP-3α) expressing MIP-3α protein. This was complemented by injections of CpG. Interestingly, MIP-3α gene therapy combined with CpG injections resulted in specific cytotoxicity. This was associated with significant suppression of tumour growth rate. These findings demonstrate the potential of strategies that utilize in vivo overexpression of chemokines.

Oxidative stress and its association with cardiovascular disease in chronic renal failure patients

Cardiovascular disease (CVD) is responsible for the majority of deaths in chronic renal failure (CRF). Oxidative stress plays a key role in pathogenesis of atherosclerosis and CVD, which is promoted by the production of reactive oxygen species (ROS) and impaired antioxidant enzymes. These ROS react with nitric oxide (NO) to produce cytotoxic reactive nitrogen species that cause oxidative injury to the endothelium. This study evaluated biomarkers of oxidative stress, NOx (total NO₂ and NO₃), and superoxide dismutase (SOD) enzyme in normal control and CRF patients as case group and correlated their association with CVD. This cross sectional study involved 173 CRF patients on different modes of treatment (hemodialysis, continuous ambulatory peritoneal dialysis (CAPD), and predialysis). Of these, 74 had CVD. The control group consisted of 33 healthy subjects who had no history of CRF and CVD. Both NOx and SOD levels were significantly lower (P<0.05, P<0.001, respectively) in the case group. Comparing between CRF patients with and without CVD, SOD level was found to be significantly lower in CRF patients with CVD (P<0.05). Logistic regression analysis showed significant association of CVD event with age, male gender, diabetes, SOD level, and lipid profile in CRF patients. Oxidative stress occurs in the CRF patients with or without CVD. This study found that NOx and SOD levels were reduced in all CRF patients with or without CVD. However, it was noted that the levels of these biomarkers of oxidative stress were significantly lower in CRF patients with CVD compared with CRF patients without CVD. Therefore, these oxidative stress markers maybe contributing factors in the pathogenesis of CVD in patients with CRF.

Comparison of the effects of anesthesia with isoflurane and total intravenous anesthesia on the intensity of body temperature reduction during anesthesia and incidence of postoperative chills

This study compared the effects of anesthesia with isoflurane and TIVA (total intravenous anesthesia) on the intensity of body temperature reduction during anesthesia and incidence of chills after lumbar disc surgery. The study was done as a single blinded randomized clinical trial. From 60 patients who underwent lumbar disc surgery, 30 subjects were placed in isoflurane group and 30 in the TIVA group. Maintenance of anesthesia was done with isoflurane (MAC=0.8-1) and N(2)O 50% in isoflurane group and in TIVA group with propofol at the dose of 100-150 mg /kg body weight /minute and remifentanil at the dose of 2.0 mg /kg body weight/minute. Chills rate was recorded in recovery room. Changes in body temperature, body surface temperature, systolic blood pressure, diastolic blood pressure and heart rate showed no significant difference between the two groups before and after induction and at different times during the operation (P<0.05). Chill rate was not significantly different between the two groups (P<0.05). It seems that TIVA (remifentanil at the dose of 2.0 µg/kg body weight/minute in combination with propofol at the dose of 100-150 µg/kg body weight/minute) and 0.81 MAC isoflurane-N(2)O 50% can be used as a safe method of anesthesia in patients with good tolerance lumbar back disc surgery without hypothermia, chills and considerable hemodynamic changes.

Fabrication and evaluation of a noncompliant molar distalizing appliance: bonded molar distalizer

OBJECTIVE

Attempts to treat class II malocclusions without extraction in non-compliant patients have led to utilization of intraoral molar distalizing appliances. The purpose of this study was to investigate dental and skeletal effects of Bonded Molar Distalizer (BMD) which is a simple molar distalizing appliance.

MATERIALS AND METHODS

Sixteen patients (12 girls, four boys) with bilateral half-cusp class II molar relationship, erupted permanent second molars and normal or vertical growth pattern were selected for bilateral distalization of maxillary molars via BMD. The screws were activated every other day, alternately. Lateral cephalograms and study models were obtained before treatment and after 11 weeks activation of the appliance.

RESULTS

Significant amounts of molar distalization, molar distal tipping and anchorage loss were observed. The mean maxillary first molar distal movement was 1.22±0.936 mm with a distal tipping of 2.97±3.74 degrees in 11 weeks. The rate of distal movement was 0.48 mm per month. Reciprocal mesial movement of the first premolars was 2.26±1.12 mm with a mesial tipping of 4.25±3.12 degrees. Maxillary incisors moved 3.55±1.46 mm and tipped 9.87±5.03 degrees mesially. Lower anterior face height (LAFH) decreased 1.28±1.36 mm.

CONCLUSION

BMD is appropriate for distalizing maxillary molars, especially in patients with critical LAFH, although significant amounts of anchorage loss occur using this appliance.

Hematopoietic protein tyrosine phosphatase suppresses extracellular stimulus-regulated kinase activation

The mitogen-activated protein kinases (MAPKs) are signaling molecules that become enzymatically activated through phosphorylation by diverse stimuli. Hematopoietic cytokines, growth factors, and stimulated lymphocyte antigen receptors may activate specific MAPKs by altering the balance of MAPK-activating protein kinases and the protein phosphatases that target their activation sites. Hematopoietic protein tyrosine phosphatase (HePTP) is a hematopoiesis-specific cytoplasmic protein tyrosine phosphatase whose expression is induced by mitogenic stimuli. To investigate the role of HePTP in hematopoietic development, we constructed mice deficient in this phosphatase using the technique of homologous recombination. Primary lymphocytes from HePTP(-/-) mice show enhanced activation of extracellular stimulus-regulated kinase (ERK) after both phorbol myristate acetate (PMA) and anti-CD3-mediated T-cell receptor (TCR) stimulation, suggesting a true physiological relationship between these two molecules. Activation of MEK, the physiological activator of ERK, by anti-CD3 or PMA is not affected by HePTP deletion. The distribution of hematopoietic lineages in bone marrow and peripheral blood samples and the in vitro proliferative capacity of bone marrow progenitors from HePTP deletion mice do not deviate from those of matched littermate controls. Similarly, lymphocyte activation and development are indistinguishable in HePTP(-/-) mice and controls. We conclude that HePTP is a physiological regulator of ERK on the basis of these studies and hypothesize that its deletion is well compensated for in the developing mouse through reduction of ERK targets or enhancement of physiologically opposed signaling pathways.

Molecular cytogenetic analysis of glial tumors using spectral karyotyping and comparative genomic hybridization

BACKGROUND

Glial tumors are the most common tumors of the central nervous system, affecting individuals of all ages. Conventional cytogenetics have been unable to identify a consistent chromosomal translocation or rearrangement in this group of tumors; thus, more advanced molecular cytogenetic approaches are required.

METHODS AND RESULTS

In this study, 16 glial tumors, including two recurrences and six glioma cell lines, were analyzed by spectral karyotyping (SKY) and comparative genomic hybridization (CGH). From 169 rearrangements detected by SKY, chromosomes 1 and 10 were the most frequently affected by translocation (18 of 169 and 16 of 169 rearrangements, respectively). Other frequently altered chromosomes included chromosomes 3 (13 of 169 rearrangements), 5 (ten of 169 rearrangements), 7 (ten of 169 rearrangements ), and 11 (ten of 169 rearrangements). A clustering of centromeric breakpoints was detected in chromosomes 3, 5, 10, 11, 16, 17, and 20. CGH analysis identified consistent gain of part or all of chromosome 7 among the 10 astrocytic tumors (five of ten specimens) in the study group. Analysis of the three gangliogliomas and one ependymoma identified a much simpler pattern of primarily numerical change.

CONCLUSION

Application of improved cytogenetic methods can increase our abilities to progress toward effective strategies of molecular diagnosis and classification of glial tumors.

Prediction of protein surface accessibility with information theory

A new, simple method based on information theory is introduced to predict the solvent accessibility of amino acid residues in various states defined by their different thresholds. Prediction is achieved by the application of information obtained from a single amino acid position or pair-information for a window of seventeen amino acids around the desired residue. Results obtained by pairwise information values are better than results from single amino acids. This reinforces the effect of the local environment on the accessibility of amino acid residues. The prediction accuracy of this method in a jackknife test system for two and three states is better than 70 and 60 %, respectively. A comparison of the results with those reported by others involving the same data set also testifies to a better prediction accuracy in our case.

Mosaicism for a small marker chromosome resulting from a familial Robertsonian translocation (21;22)

A mosaic marker chromosome found in amniotic fluid was shown to have originated from the proximal part of the long arm of chromosome 22. This marker is unusual because it is the result of a deletion of a maternally inherited Robertsonian 21;22 translocation. It is suggested that the deletion and marker formation probably occurred post zygotically in the fetus. This rare case illustrates the difficulty in estimating risk of fetal abnormalities associated with de novo marker chromosomes. In this example, although the 'extra' marker chromosome contains euchromatin, the karyotype may still be 'balanced'.

Verotoxin induces apoptosis and the complete, rapid, long-term elimination of human astrocytoma xenografts in nude mice

Verotoxin 1 (VT1) is an E. coli elaborated subunit toxin active only against (tumor) cell lines that express the VT1 receptor, globotriaosyl ceramide-Gb3. Astrocytomas can be highly malignant brain tumors that remain refractory to clinical treatment. Some human astrocytoma cell lines are particularly sensitive to VT1 in vitro. To address whether this represents a feasible approach to the elimination of these tumors in man, human astrocytoma tumor xenografts in nude mice were treated with verotoxin. Following a single low-dose intratumoral injection of VT1, complete regression of a 1-cm-diameter tumor within 10 days was observed in all treated animals, without reoccurrence (up to 60 days). Apoptosis was demonstrated in both tumor and vascular cells within the treated xenograft. Verotoxin binding to tumor cells and blood vessels in sections of primary glioblastoma multiforme was found.

Intracellular targeting of the endoplasmic reticulum/nuclear envelope by retrograde transport may determine cell hypersensitivity to verotoxin via globotriaosyl ceramide fatty acid isoform traffic

The pentameric B subunit of verotoxin (VT) mediates the attachment to cell surface globotriaosyl ceramide (Gb3) to facilitate receptor-mediated endocytosis of the toxin. In highly toxin-sensitive tumor cells, the holotoxin and VT1 B subunit is targeted intracellularly to elements of the endoplasmic reticulum (ER)/nuclear membrane. In less sensitive cells, the toxin is targeted to components of the Golgi apparatus. We have studied two cell systems: the induced VT hypersensitivity of human astrocytoma cell lines cultured in the presence of sodium butyrate (compared to sodium propionate and capronate) and the increased VT sensitivity of multiple drug-resistant mutants as compared to parental human ovarian carcinoma cells. In both cases, a difference in the intracellular retrograde transport of the receptor-bound internalized toxin to the ER/nuclear envelope, as opposed to the Golgi, correlated with a >1,000-fold increase in cell sensitivity to VT. This change in intracellular routing may be due to sorting of Gb3 fatty acid isoforms, since nuclear targeting was found in turn to correlate with the preferential synthesis of Gb3 containing shorter chain (primarily C16) fatty acid species. We propose that the isoform-dependent traffic of Gb3 from the cell surface to the ER/nuclear membrane provides a new signal transduction pathway for Gb3 binding proteins.

Globotriaosyl ceramide (Gb3) expression in human tumour cells: intracellular trafficking defines a new retrograde transport pathway from the cell surface to the nucleus, which correlates with sensitivity to verotoxin

The verotoxin receptor globotriaosyl ceramide (Gb3) is overexpressed in an ovarian tumour resistant to chemotherapy. An overlay of frozen tumour sections shows extensive staining of the tumour cells with verotoxin B subunit. In addition, blood vessels within the tumour mass are stained. The sensitivity of ovarian tumour cells in vitro to verotoxin can be modulated by culturing the cells in sodium butyrate to obtain an approximately 5000-fold increase in susceptibility. This increased susceptibility is correlated with the intracellular targeting of verotoxin as monitored by using FITC-VT B subunit, in that prior to sodium butyrate treatment the toxin is internalized to a juxtanuclear (likely) Golgi location whereas, following butyrate treatment the intracellular toxin is distributed around the nucleus, consistent with endoplasmic reticulum and nuclear envelope location. This perinuclear location is similar to that found for drug-resistant variants of ovarian tumour cell lines. These results suggest that intracellular targeting of verotoxin to the perinuclear area results in increased cytotoxicity. Potentially such targeting may also occur in other human tumours.

Verotoxins inhibit the growth of and induce apoptosis in human astrocytoma cells

Verotoxin 1 (VT1) is an E. coli toxin comprising an A subunit with N-glycanase activity, and five smaller B subunits capable of binding to the functional receptor globotriaosylceramide (Galalpha1-4-Galbeta1-4-Glcceramide-Gb3). VT is implicated in hemorrhagic colitis and the more serious hemolytic uremic syndrome. VT1 is active against various tumor cell lines in vitro and in vivo. To extend the anti-cancer spectrum of activity of VT to human brain tumors, in the present analysis we studied the effects of VT on the growth of 6 permanent human astrocytoma cell lines. All astrocytoma cell lines analyzed express Gb3 and were sensitive to VT-1 at a dose of 50 ng/ml, but sensitivity was not proportional to the relative Gb3 concentration. VT induced apoptosis in these cells was shown by electron microscopy. Morphological evidence (nuclear shrinkage and chromatin condensation) of apoptosis could be clearly distinguished 1.5 hrs after toxin addition. Ultrastructural preservation of organelles was observed in conjunction with blebbing of the plasma membrane, condensation of chromatin within the nucleus and nuclear shrinkage. Apoptosis was also induced by the recombinant toxin B subunit alone, suggesting that the ligation of Gb3 is the primary induction mechanism. These studies indicate that verotoxin/Gb3 targetting may provide a novel basis for the inhibition of astrocytoma tumour cell growth.

Death of tumor cells after intracellular acidification is dependent on stress-activated protein kinases (SAPK/JNK) pathway activation and cannot be inhibited by Bcl-2 expression or interleukin 1beta-converting enzyme inhibition

The extracellular microenvironment of tumors differs from that of most normal tissues. Many tumors have relatively acidic extracellular pH, although the intracellular pH of tumor cells remains normal due to the efficient maintenance of a large proton gradient across the membrane. This difference between tumors and normal tissues might be exploited therapeutically by disruption of the mechanisms that regulate intracellular pH, so that tumor cells are killed by intracellular acid-induced injury. To investigate the mechanisms by which intracellular acidification leads to cell death, we have studied the roles of the antiapoptotic gene bcl-2 and its proapoptotic binding partner bax, the stress-activated protein kinases (SAPK/JNK), and the caspase proteases in mediating acid-induced cell death. Whereas the expression of bcl-2 in human bladder cancer MGH-U1 cells had no effect on acid-induced death, overexpression of bax enhanced cell death, consistent with its proapoptotic function. Inhibition of SAPK, through the expression of a dominant negative mutant of its activator, SEK1, protected cells from acid-induced cell death. Caspase activation, as measured by poly(ADP-ribose) polymerase cleavage, was absent after lethal intracellular acidification. Consistent with this observation, inhibition of interleukin 1beta-converting enzyme proteases by the peptide z-Val-Ala-Asp(OMe)-CH2F did not protect against acid-induced cell killing. We conclude that acid-induced cell death depends on bax and on SAPK signaling pathways, but not on the caspase proteases. Therapeutic manipulation of bax and SAPK may enhance acid-induced tumor cell killing.

Globotriaosyl ceramide (Gb3) expression in human tumour cells: intracellular trafficking defines a new retrograde transport pathway from the cell surface to the nucleus, which correlates with sensitivity to verotoxin

The verotoxin receptor globotriaosyl ceramide (Gb3) is overexpressed in an ovarian tumour resistant to chemotherapy. An overlay of frozen tumour sections shows extensive staining of the tumour cells with verotoxin B subunit. In addition, blood vessels within the tumour mass are stained. The sensitivity of ovarian tumour cells in vitro to verotoxin can be modulated by culturing the cells in sodium butyrate to obtain an approximately 5000-fold increase in susceptibility. This increased susceptibility is correlated with the intracellular targeting of verotoxin as monitored by using FITC-VT B subunit, in that prior to sodium butyrate treatment the toxin is internalized to a juxtanuclear (likely) Golgi location whereas, following butyrate treatment the intracellular toxin is distributed around the nucleus, consistent with endoplasmic reticulum and nuclear envelope location. This perinuclear location is similar to that found for drug-resistant variants of ovarian tumour cell lines. These results suggest that intracellular targeting of verotoxin to the perinuclear area results in increased cytotoxicity. Potentially such targeting may also occur in other human tumours.

Expression of the verotoxin receptor glycolipid, globotriaosylceramide, in ovarian hyperplasias

The presence of cell surface receptor glycolipid, globotriaosylceramide (Gb3), is essential to confer susceptibility to the E. coli-derived verotoxin (VT). Our earlier studies showed that Gb3 is expressed in ovarian carcinoma cell lines. The Gb3 content of normal ovary, benign and malignant primary ovarian tumors, and their metastases have now been compared by verotoxin thin-layer chromatogram (TLC) overlay of the glycolipid tissue extracts. FITC-labeled VT1 B subunit binding to frozen tumor sections was also monitored histochemically. Low to undetectable levels of Gb3 were found in "normal" ovarian tissue. Gb3 was markedly increased in both benign and malignant tumors, suggesting that increased Gb3 may be related to proliferation, rather than malignancy per se. Mucinous tumors showed the least Gb3 elevation; serous tumors were variable, showing higher levels of Gb3 in less differentiated malignant tumors. By far the highest Gb3 content was observed for secondary ovarian metastases and tumors refractory to chemotherapy. Frozen sections of neoplastic ovarian tissue overlaid with fluorescein-conjugated VT1 B subunit show extensive binding to tumor cells, particularly in poorly differentiated samples and blood vessels adjacent to, and within, the tumor mass. Tumor foci were stained but stromal tissue was consistently negative both in primary tumors and metastases. VT staining of well-differentiated primary ovarian tumor sections was weak, corresponding to their low Gb3 content, but strong staining was observed in sections from a highly differentiated primary tumor from a patient who was unexpectedly refractory to clinical chemotherapy. These studies suggest that verotoxin/Gb3 targeting may provide the basis for new treatments for ovarian cancer.

Influence of phospholipid chain length on verotoxin/globotriaosyl ceramide binding in model membranes: comparison of a supported bilayer film and liposomes

The importance of the surrounding lipid environment on the availability of glycolipid carbohydrate for ligand binding was demonstrated by studying the influence of phosphatidylcholine fatty acid chain length on binding of verotoxins (VT1 and VT2c) to their specific cell surface receptor, globotriaosylceramide (Gb3) in the presence of auxiliary lipids both in a microtitre plate surface bilayer film and in a liposome membrane model system. In the microtitre assay, both VT1 and VT2c binding to Gb3 was increased as a function of decreasing PC acyl chain length likely resulting in increased Gb3 exposure. In the liposome assay VT1 binding was similarly modulated, however the effect of VT2c binding was more complex and did not follow a simple function of increased carbohydrate exposure. Earlier work established that C22:1 and C18:1Gb3 fatty acid homologues were the preferred Gb3 receptor containing liposomes, but in C14PC liposomes, binding to C22:1Gb3 (but not C18:1Gb3) was elevated such that this Gb3 species now became the preferred receptor for both toxins. This change in verotoxin/Gb3 homologue binding selectivity in the presence of C14PC did not occur in the microtitre bilayer format. These results are consistent with our proposal that these toxins recognize different epitopes on the Gb3 oligosaccharide. We infer that relative availability of these epitopes for toxin binding in an artificial bilayer is influenced not only by the exposure due to the discrepancy between the fatty acyl chain lengths of Gb3 and PC, but by the physical mode of presentation of the bilayer structure. Such acyl chain length differences have a more marked effect in a supported bilayer film whereas only the largest discrepancies affect Gb3 receptor function in liposomes. The basis of phospholipid modulation of glycolipid carbohydrate accessibility for receptor function is likely complex and will involve phase separation, gel/liquid crystalline transition, packing and lateral mobility within the bilayer, suggesting that such parameters should be considered in the assessment of glycolipid receptor function in cells.

The bacterial colicin active against tumor cells in vitro and in vivo is verotoxin 1

We have identified verotoxin 1 (VT1) as the active component within an antineoplastic bacteriocin preparation from Escherichia coli HSC10 studied over two decades. Recombinant VT1 can simulate the toxicity of anticancer proteins (ACP), and the antineoplastic activity of ACP (and VT1) was abrogated by treatment with anti-VT1 antibody. Similarly, VT1 mimics the protective effect of ACP in a murine metastatic fibrosarcoma model. Prior immunization with VT1 B subunit prevents the effect of VT1 or ACP in this model. The activity of ACP against a variety of human ovarian cell lines was mimicked by VT1, and multidrug-resistant variants were significantly hypersensitive. Primary ovarian tumors and metastases contain elevated levels of globotriaosylceramide compared with normal ovaries, and overlay of frozen tumor sections showed selective VT binding to tumor tissue and the lumen of invading blood vessels. Our contention that VT1 could provide an additional approach to the management of certain human neoplasms is discussed.

Universal method for the facile production of glycolipid/lipid matrices for the affinity purification of binding ligands

Glycolipid recognition is a common motif in cellular physiology and bacterial pathogenesis. Such protein/lipid interactions are most conveniently demonstrated by the thin-layer chromatogram overlay. We have designed a simple affinity matrix for the purification of such glycolipid (or lipid) binding ligands based on the same principle, i.e., glycolipid (or lipid) adsorbed onto silica. The versatility of the procedure is demonstrated by the purification of several anti-glycolipid antibodies and anti-phosphatidyl ethanolamine (anti-PE) and the affinity purification of the Escherichia coli-derived verotoxin which binds to globotriaosyl ceramide.

Balloon dilatation of critical stenosis of the pulmonary valve in neonates

Percutaneous balloon dilatation was attempted in 15 consecutive neonates (mean age 7.3 (range 1-27) days and weight 3.2 (range 2.5-4.1) kg) with critical stenosis of the pulmonary valve. Dilatation was successful in 11 (73%) patients. The mean balloon to annulus ratio was 1.1 (range 0.6-1.77). The ratio of right ventricle to femoral artery systolic pressure decreased from a mean (1 SD) of 1.4 (0.32) before to 0.8 (0.24) after dilatation and the transvalvar gradient decreased from 81 (29.7) mm Hg before to 33 (27.7) mm Hg after dilatation. All four (27%) patients in whom dilatation was unsuccessful underwent surgical valvotomy. Complications of balloon dilatation occurred in three (20%) patients; these included retroperitoneal haematoma (one) and iliofemoral venous occlusion (two). In one (7%) patient severe hypoxia and hypotension developed when the valve was crossed with a guide wire and balloon catheter. Despite successful dilatation he died 7 days after the procedure. During a mean (1 SD) follow up of 2 (1.7) years, seven (64%) of the 11 patients remained free of important restenosis. One patient required repeat dilatation three weeks after the initial procedure. In three (27%) patients restenosis developed 4-9 months after dilatation and all three had surgical valvotomy. Of the four patients initially referred for surgery three required a second operation and one required balloon dilatation. Percutaneous balloon dilatation gave effective relief of critical pulmonary stenosis in most neonates but complications and restenosis requiring surgery were common.