Abstract P6-17-39: BAT8001, a potent anti-HER2 antibody-drug conjugate with a novel stable linker for the treatment of HER2-positive breast cancer

Overexpression of HER2 occurs in approximately 20% of breast cancers and is associated with shortened survival. Trastuzumab emtansine (T-DM1), an anti-HER2 ADC, has shown efficacy in HER2-positive breast cancer patients and was approved by the FDA and EMA for advanced HER2-positive breast cancer. However T-DM1 causes grade 3 and 4 thrombocytopenia in up to 14.5% of patients as its major toxicity. The thrombocytopenia is likely caused by one of T-DM1's catabolites and payload, DM1, indicating T-DM1's linker can be cleaved. Here we adopted a novel noncleavable linker and created an anti-HER2 ADC, BAT8001, which is expected be efficacious in HER2-positive breast cancer and have a better side effect profile relative to T-DM1 due to the stability of BAT8001's noncleavable linker. BAT8001 is internalized in HER2-positive cancer cells. It inhibits proliferation of HER2-positive tumor cells with IC50s of ˜0.1 nM, similar to the potency of T-DM1. BAT8001 also induces apoptosis in HER2-positive cancer cells. In both cell-line and patient-derived mouse xenograft (PDX) models, BAT8001 demonstrates strong inhibition activity on tumor growth. For example, in a cell-line model of breast cancer (BT474), BAT8001 demonstrates potent activity with complete responses in all animals tested at the 15mg/kg dose level. Pharmacokinetics studies in monkey reveals BAT8001 has similar Cmax, AUC, and t1/2 as T-DM1. The major catabolite of BAT8001 is the Cys-linker-payload containing product. No free payload is observed. This compares favorably with T-DM1 where free DM1, T-DM1's payload, is one of the major catabolites. In a multiple dose toxicity study, BAT8001 had a NOAEL of 15 mg/kg versus 10 mg/kg for T-DM1. BAT8001 exhibits similar potency to T-DM1 on inhibiting HER2-positive cell proliferation and tumor growth, yet demonstrates better multiple dose toxicity than T-DM1. The improved toxicity profile of BAT8001 suggests that the novel noncleavable linker utilized in BAT8001 is more stable than the linker utilized in T-DM1. BAT8001 is very efficacious in cell-line xenograft models of breast cancer. The preclinical profile of BAT8001 warrants further development for the treatment of breast cancer and other HER2-positive cancers.

Citation Format: Tang W, Deng X, Ou Z, Gan J, Dong Q, Tan B, Lu L, Chen B, Bao C, Li S, Thomas B, Yu J-C. BAT8001, a potent anti-HER2 antibody-drug conjugate with a novel stable linker for the treatment of HER2-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-39.

Risk factors associated with liver steatosis and fibrosis in chronic hepatitis B patient with component of metabolic syndrome

Background

We investigated whether metabolic syndrome exacerbated the risk of liver fibrosis among chronic hepatitis B patients and risk factors associated with liver steatosis and fibrosis in chronic hepatitis B patients with components of metabolic syndrome.

Methods

This study included 1236 chronic hepatitis B patients with at least one component of metabolic syndrome. The controlled attenuation parameter and liver stiffness, patient information and relevant laboratory data were recorded.

Results

Controlled attenuation parameter was increased progressively with the number of metabolic syndrome components (p < 0.001). Multivariate analysis indicated younger age, high gamma-glutamyltransferase level, high waist-hip ratio, and high body mass index were independent risk factors associated with nonalcoholic fatty liver disease among chronic hepatitis B patients with metabolic syndrome. In the fibrosis and non-fibrosis groups, most of blood lipid was relatively lower in fibrosis group. An increased proportion of chronic hepatitis B patients with liver fibrosis was found concomitant with an increasing number of components of metabolic syndrome. Male gender, older age, smoking, aspartate aminotransferase levels, high body mass index, and low platelet level were identified as independent risk factors associated with liver fibrosis.

Conclusions

For chronic hepatitis B patients with coexisting components of metabolic syndrome, stratification by independent risk factors for nonalcoholic fatty liver disease and fibrosis can help with management of their disease.

High-mobility group box 1 regulates cytoprotective autophagy in a mouse spermatocyte cell line (GC-2spd) exposed to cadmium

BACKGROUND

Cadmium (Cd) is an environmental and industrial pollutant that induces a broad spectrum of toxicological effects, influences a variety of human organs, and is associated with poor semen quality and male infertility. Increasing evidence demonstrates that Cd induces testicular germ cell apoptosis in rodent animals. However, the specific effect of Cd exposure on autophagy in germ cells is poorly understood.

METHODS

We investigate the role of high-mobility group box 1 protein (HMGB1), a ubiquitous nuclear protein, on Cd-evoked autophagy in a mouse spermatocyte cell line (GC-2spd).

RESULTS

Our data have shown that autophagy was significantly elevated in GC-2spd cells exposed to Cd. Furthermore, there was a reduction in rapamycin (RAP)-mediated apoptosis. In addition, Cd exposure reduced cell viability, which is an effect that could be significantly inhibited by RAP treatment. These results indicate that autophagy appears to serve a positive function in reducing Cd-induced cytotoxicity. In addition, HMGB1 increased coincident with the processing of LC3-I to LC3-II. Thus, the upregulation of HMGB1 increases LC3-II levels.

CONCLUSIONS

Our data suggest that HMGB1-induced autophagy appears to act as a defense/survival mechanism against Cd cytotoxicity in GC-2spd cells.

Androgen receptor promotes melanoma metastasis via altering the miRNA-539-3p/USP13/MITF/AXL signals

Early studies demonstrated that male melanoma patients have worse survival than female patients, yet the detailed mechanisms for this gender difference remain unclear. We analyzed around 100 cases of human melanoma and found that androgen receptor (AR) positive melanoma patients have worse survival outcomes compared with AR-negative melanoma patients. Here we report that AR can have positive roles to increase melanoma cell invasion in multiple cell lines in vitro and a mouse model in vivo. Mechanism dissection suggest that AR increases melanoma cell invasion via modulating the MITF-AXL signals via altering the miRNA-539-3p/USP13 signaling to increase MITF protein degradation through a reduction of de-ubiquitination. Restoring MITF can reverse AR-enhanced melanoma cell invasion. Together, our results demonstrate that AR can promote melanoma metastasis via altering the miRNA-539-3p/USP13/MITF/AXL signal and targeting this newly identified signal with AR degradation enhancer ASC-J9 may help us to better suppress the melanoma metastasis.

Identification of novel genes and pathways in carotid atheroma using integrated bioinformatic methods

Atherosclerosis is the primary cause of cardiovascular events and its molecular mechanism urgently needs to be clarified. In our study, atheromatous plaques (ATH) and macroscopically intact tissue (MIT) sampled from 32 patients were compared and an integrated series of bioinformatic microarray analyses were used to identify altered genes and pathways. Our work showed 816 genes were differentially expressed between ATH and MIT, including 443 that were up-regulated and 373 that were down-regulated in ATH tissues. GO functional-enrichment analysis for differentially expressed genes (DEGs) indicated that genes related to the "immune response" and "muscle contraction" were altered in ATHs. KEGG pathway-enrichment analysis showed that up-regulated DEGs were significantly enriched in the "FcεRI-mediated signaling pathway", while down-regulated genes were significantly enriched in the "transforming growth factor-β signaling pathway". Protein-protein interaction network and module analysis demonstrated that VAV1, SYK, LYN and PTPN6 may play critical roles in the network. Additionally, similar observations were seen in a validation study where SYK, LYN and PTPN6 were markedly elevated in ATH. All in all, identification of these genes and pathways not only provides new insights into the pathogenesis of atherosclerosis, but may also aid in the development of prognostic and therapeutic biomarkers for advanced atheroma.

HSPB1 as a novel regulator of ferroptotic cancer cell death

Ferroptosis is an iron-dependent form of non-apoptotic cell death, but its molecular mechanism remains largely unknown. Here, we demonstrate that heat shock protein beta-1 (HSPB1) is a negative regulator of ferroptotic cancer cell death. Erastin, a specific ferroptosis-inducing compound, stimulates heat shock factor 1 (HSF1)-dependent HSPB1 expression in cancer cells. Knockdown of HSF1 and HSPB1 enhances erastin-induced ferroptosis, whereas heat shock pretreatment and overexpression of HSPB1 inhibits erastin-induced ferroptosis. Protein kinase C-mediated HSPB1 phosphorylation confers protection against ferroptosis by reducing iron-mediated production of lipid reactive oxygen species. Moreover, inhibition of the HSF1-HSPB1 pathway and HSPB1 phosphorylation increases the anticancer activity of erastin in human xenograft mouse tumor models. Our findings reveal an essential role for HSPB1 in iron metabolism with important effects on ferroptosis-mediated cancer therapy.

Association between dietary patterns and coronary heart disease: a meta-analysis of prospective cohort studies

The associations of dietary patterns with coronary heart disease (CHD) risk remain unclear. Thereby, a meta-analysis was conducted to examine potential relations between dietary patterns and CHD. PubMed and EMBASE databases were searched up to March 2014 for eligible prospective cohort studies regarding the relationships between common dietary patterns and CHD. Random-effects models were applied to calculate the summary relative risk estimates (SRRE) for the highest versus the lowest category of dietary pattern. Sensitivity analyses were conducted and publication bias was assessed using Begg or Egger's tests. Twelve prospective cohort studies were included involving 409,780 participants and 6298 CHD cases. There was an inverse association between prudent/healthy dietary pattern and CHD risk (SRRE = 0.80, 95% CI: 0.74-0.87, P-value for heterogeneity = 0.497, I(2) = 0%). Furthermore, no significant association was observed between western/unhealthy dietary pattern and risk of CHD (SRRE = 1.05, 95% CI: 0.86-1.27, P-value for heterogeneity = 0.007, I(2) = 61.9%). However, increased risk was detected between western/unhealthy dietary pattern and CHD in the United States (USA) (SRRE = 1.45, 95% CI: 1.15-1.82, P-value for heterogeneity = 0.930, I(2) = 0%). In conclusion, our analysis provides evidence of an inverse association between prudent/healthy dietary pattern and CHD risk, and suggests null association between western/unhealthy dietary pattern and CHD. However, greater adherence to western/unhealthy pattern possibily increases by 45% the risk of CHD in USA. Further efforts are warranted to confirm these findings and clarify the role of dietary patterns and CHD risk.

Association of STAT3 common variations with obesity and hypertriglyceridemia: protective and contributive effects

Signal transducer and activator of transcription 3 (STAT3) plays an important role in energy metabolism. Here we explore whether STAT3 common variations influence risks of obesity and other metabolic disorders in a Chinese Han population. Two tagging single nucleotide polymorphisms (tagSNPs), rs1053005 and rs957970, were used to capture the common variations of STAT3. Relationships between genotypes and obesity, body mass index, plasma triglyceride and other metabolic diseases related parameters were analyzed for association study in 1742 subjects. Generalized linear model and logistic regression model were used for quantitative data analysis and case-control study, respectively. rs1053005 was significantly associated with body mass index and waist circumference (p = 0.013 and p = 0.02, respectively). rs957970 was significantly associated with plasma level of triglyceride (p = 0.007). GG genotype at rs1053005 had lower risks of both general obesity and central obesity (OR = 0.40, p = 0.034; OR = 0.42, p = 0.007, respectively) compared with AA genotype. CT genotype at rs957970 had a higher risk of hypertriglyceridemia (OR = 1.43, p = 0.015) compared with TT genotype. Neither of the two SNPs was associated with othermetabolic diseases related parameters. Our observations indicated that common variations of STAT3 could significantly affect the risk of obesity and hypertriglyceridemia in Chinese Han population.

The nature and origin of nucleus-like intracellular inclusions in Paleoproterozoic eukaryote microfossils

The well-known debate on the nature and origin of intracellular inclusions (ICIs) in silicified microfossils from the early Neoproterozoic Bitter Springs Formation has recently been revived by reports of possible fossilized nuclei in phosphatized animal embryo-like fossils from the Ediacaran Doushantuo Formation of South China. The revisitation of this discussion prompted a critical and comprehensive investigation of ICIs in some of the oldest indisputable eukaryote microfossils-the ornamented acritarchs Dictyosphaera delicata and Shuiyousphaeridium macroreticulatum from the Paleoproterozoic Ruyang Group of North China-using a suite of characterization approaches: scanning electron microscopy (SEM), transmission electron microscopy (TEM), and focused ion beam scanning electron microscopy (FIB-SEM). Although the Ruyang acritarchs must have had nuclei when alive, our data suggest that their ICIs represent neither fossilized nuclei nor taphonomically condensed cytoplasm. We instead propose that these ICIs likely represent biologically contracted and consolidated eukaryotic protoplasts (the combination of the nucleus, surrounding cytoplasm, and plasma membrane). As opposed to degradational contraction of prokaryotic cells within a mucoidal sheath-a model proposed to explain the Bitter Springs ICIs-our model implies that protoplast condensation in the Ruyang acritarchs was an in vivo biologically programmed response to adverse conditions in preparation for encystment. While the discovery of bona fide nuclei in Paleoproterozoic acritarchs would be a substantial landmark in our understanding of eukaryote evolution, the various processes (such as degradational and biological condensation of protoplasts) capable of producing nuclei-mimicking structures require that interpretation of ICIs as fossilized nuclei be based on comprehensive investigations.

22q13.3 deletion syndrome: clinical and molecular analysis using array CGH

The 22q13.3 deletion syndrome results from loss of terminal segments of varying sizes at 22qter. Few genotype-phenotype correlations have been found but all patients have mental retardation and severe delay, or absence of, expressive speech. We carried out clinical and molecular characterization of 13 patients. Developmental delay and speech abnormalities were common to all and comparable in frequency and severity to previously reported cases. Array-based comparative genomic hybridization showed the deletions to vary from 95 kb to 8.5 Mb. We also carried out high-resolution 244K array comparative genomic hybridization in 10 of 13 patients, that defined the proximal and distal breakpoints of each deletion and helped determine the size, extent, and gene content within the deletion. Two patients had a smaller 95 kb terminal deletion with breakpoints within the SHANK3 gene while three other patients had a similar 5.5 Mb deletion implying the recurrent nature of these deletions. The two largest deletions were found in patients with ring chromosome 22. No correlation could be made with deletion size and phenotype although complete/partial SHANK3 was deleted in all patients. There are very few reports on array comparative genomic hybridization analysis on patients with the 22q13.3 deletion syndrome, and we aim to accurately characterize these patients both clinically and at the molecular level, to pave the way for further genotype-phenotype correlations. (c) 2010 Wiley-Liss, Inc.

Coexpression and Synergistic Role of Multiple Atypical Chemokine Binders in Breast Cancer

Background: The expression and role of Duffy antigen receptor for chemokine (DARC), D6 and ChemoCentryx chemokine receptor (CCX-CKR) in breast cancer have already been studied independently in the past several years. However, the relationship and importance of these atypical chemokine binders (ACB) are still unclear. In this large scale clinical study, we invastigated the characteristics of multiple ACB simultaneously. Material and Methods: The protein levels of DARC, D6 and CCX-CKR were analyzed by immunohistochemistry in 517 patients with invasive breast cancer, 29 patients with noninvasive breast cancer. All of these cases come from the Cancer Hospital of Fudan University during 2001-2006, with complete clinicopathological data and follow-up data, including survival information. Results: In the invasive breast cancer patients, triple, double and single positive expression of these ACB were 135 cases (26.1%), 154 cases (29.8%) and 121 cases (23.4%), respectively. On the other hand, 107 cases (20.7%) were complete negative. The triple positive staining was significantly conversely correlated with lymph node metastasis, disease stage, relapse-free survival (RFS) as well as overall survival (OS). DARC, D6, and CCX-CKR were independent factors that influenced lymph node metastasis and their coexpression was favorable prognostic factor for RFS and OS. Discussion: Our results confirmed that DARC, D6, and CCX-CKR play a negative role in breast cancer. Furthermore, their triple or double high coexpression is more favorable for the patients, suggesting that multiple ACB may provide better protection against metastasis and relapse by synergistically regulating chemokine network in breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4166.

Overexpression or Lack of beta 2-Adrenergic Receptor Correlate with Progression of Breast Cancer

Background: Recent studies showed that stress can modulate biological behavior of ovarian carcinoma through adrenergic receptors. Since both nonselective beta-adrenergic receptor antagonist propranolol and selective beta 2-adrenergic receptor (b2AR) antagonist ICI 118,551 instead of b1AR antagonist atenolol could eliminate most of the effects, b2AR is accordingly regarded as the key molecule. In this study, we investigated the role of b2AR in breast cancer. Material and Methods: Gene expression of b2AR was analyzed by RT-PCR in human breast cancer cell lines MDA-MB-231, MDA-MB-435, MDA-MB-468, MCF-7, T47D, BT-549, HCC1937, BCaP-37 and normal mammary epithelial-like cell line HBL-100. b2AR cDNA was transfected into MDA-MB-435 cells. Protein level of b2AR was analyzed by immunohistochemistry in clinical samples, including 25 normal human breast or benign disease breast tissues and 202 breast cancer tissues. Results: b2AR was detected in majority of breast cancer cell lines, except for MDA-MB-435, MCF-7 and T47D, and all of normal or benign disease breast tissues. Both nonselective beta-adrenergic receptor agonist norepinephrine (NE) and selective b2AR agonist terbutaline promoted proliferation and invasion of spontaneous b2AR-positive MDA-MB-231 cells and transfectant MDA-MB-435-b2AR cells, these effects were completely inhibited by selective b2AR antagonist ICI 118,551. In the breast cancer patients, 125 samples (61.9%) expressed b2AR weakly or moderately just as normal breast or benign diseases tissue, and 43 (21.3%) presented significantly stronger b2AR expression, while no b2AR staining was found in other 34 samples (16.8%). Higher expression or lack of b2AR were associated with axillary lymph nodes metastasis and poor disease free survival (DFS). Discussion: Based on our preliminary results, the breast cancer patients could be classified into three subgroups: b2AR “normal”, high expression and negative groups. Overexpression or lack of b2AR associated with metastasis and clinical prognosis in breast cancer. Obviously, abnormal expression of b2AR may influence the outcome of breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4165.

Microdeletions including YWHAE in the Miller-Dieker syndrome region on chromosome 17p13.3 result in facial dysmorphisms, growth restriction, and cognitive impairment

BACKGROUND

Deletions in the 17p13.3 region are associated with abnormal neuronal migration. Point mutations or deletion copy number variants of the PAFAH1B1 gene in this genomic region cause lissencephaly, whereas extended deletions involving both PAFAH1B1 and YWHAE result in Miller-Dieker syndrome characterised by facial dysmorphisms and a more severe grade of lissencephaly. The phenotypic consequences of YWHAE deletion without deletion of PAFAH1B1 have not been studied systematically.

METHODS

We performed a detailed clinical and molecular characterization of five patients with deletions involving YWHAE but not PAFAH1B1, two with deletion including PAFAH1B1 but not YWHAE, and one with deletion of YWHAE and mosaic for deletion of PAFAH1B1.

RESULTS

Three deletions were terminal whereas five were interstitial. Patients with deletions including YWHAE but not PAFAH1B1 presented with significant growth restriction, cognitive impairment, shared craniofacial features, and variable structural abnormalities of the brain. Growth restriction was not observed in one patient with deletion of YWHAE and TUSC5, implying that other genes in the region may have a role in regulation of growth with CRK being the most likely candidate. Using array based comparative genomic hybridisation and long range polymerase chain reaction, we have delineated the breakpoints of these nonrecurrent deletions and show that the interstitial genomic rearrangements are likely generated by diverse mechanisms, including the recently described Fork Stalling and Template Switching (FoSTeS)/Microhomology Mediated Break Induced Replication (MMBIR).

CONCLUSIONS

Microdeletions of chromosome 17p13.3 involving YWHAE present with growth restriction, craniofacial dysmorphisms, structural abnormalities of brain and cognitive impairment. The interstitial deletions are mediated by diverse molecular mechanisms.

Identification of critical regions for clinical features of distal 10q deletion syndrome

Array comparative genomic hybridization studies were performed to further characterize cytogenetic abnormalities found originally by karyotype and fluorescence in situ hybridization in five clinical cases of distal 10q deletions, including several with complex cytogenetic rearrangements and one with a partial male-to-female sex-reversal phenotype. These results have enabled us to narrow the previously proposed critical regions for the craniofacial, urogenital, and neuropsychiatric disease-related manifestations associated with distal 10q deletion syndrome. Furthermore, we propose that haploinsufficiency of the DOCK1 gene may play a crucial role in the pathogenesis of the 10q deletion syndrome. We hypothesize that alteration of DOCK1 and/or other genes involved in regulation and signaling of multiple pathways can explain the wide range of phenotypic variability between patients with similar or identical cytogenetic abnormalities.

20p12.3 microdeletion predisposes to Wolff-Parkinson-White syndrome with variable neurocognitive deficits

BACKGROUND

Wolff-Parkinson-White syndrome (WPW) is a bypass re-entrant tachycardia that results from an abnormal connection between the atria and ventricles. Mutations in PRKAG2 have been described in patients with familial WPW syndrome and hypertrophic cardiomyopathy. Based on the role of bone morphogenetic protein (BMP) signalling in the development of annulus fibrosus in mice, it has been proposed that BMP signalling through the type 1a receptor and other downstream components may play a role in pre-excitation.

METHODS AND RESULTS

Using the array comparative genomic hybridisation (CGH), we identified five individuals with non-recurrent deletions of 20p12.3. Four of these individuals had WPW syndrome with variable dysmorphisms and neurocognitive delay. With the exception of one maternally inherited deletion, all occurred de novo, and the smallest of these harboured a single gene, BMP2. In two individuals with additional features of Alagille syndrome, deletion of both JAG1 and BMP2 were identified. Deletion of this region has not been described as a copy number variant in the Database of Genomic Variants and has not been identified in 13 321 individuals from other cohort examined by array CGH in our laboratory.

CONCLUSIONS

Our findings demonstrate a novel genomic disorder characterised by deletion of BMP2 with variable cognitive deficits and dysmorphic features and show that individuals bearing microdeletions in 20p12.3 often present with WPW syndrome.

Application of metaphase HR-CGH and targeted Chromosomal Microarray Analyses to genomic characterization of 116 patients with mental retardation and dysmorphic features

Recent advances in molecular cytogenetics enable identification of small chromosomal aberrations that are undetectable by routine chromosome banding in 5-20% of patients with mental retardation/developmental delay (MR/DD) and dysmorphism. The aim of this study was to compare the clinical usefulness of two molecular cytogenetic techniques, metaphase high-resolution comparative genomic hybridization (HR-CGH) and targeted array CGH, also known as Chromosomal Microarray Analysis (CMA). A total of 116 patients with unexplained mild to severe MR and other features suggestive of a chromosomal abnormality with apparently normal or balanced karyotypes were analyzed using HR-CGH (43 patients) and/or CMA (91 patients). Metaphase HR-CGH detected seven interstitial deletions (16.3%). Rare deletions of chromosomes 16 (16p11.2p12.1) and 8 (8q21.11q21.2) were identified. Targeted CMA revealed copy-number changes in 19 of 91 patients (20.8%), among which 11 (11.8%) were clinically relevant, 6 (6.5%) were interpreted as polymorphic variants and 2 (2.1%) were of uncertain significance. The changes varied in size from 0.5 to 12.9 Mb. In summary, our results show that metaphase HR-CGH and array CGH techniques have become important components in cytogenetic diagnostics, particularly for detecting cryptic constitutional chromosome imbalances in patients with MR, in whom the underlying genetic defect is unknown. Additionally, application of both methods together increased the detection rates of genomic imbalances in the tested groups.

Characterization of de novo microdeletions involving 17q11.2q12 identified through chromosomal comparative genomic hybridization

High-resolution array-comparative genome hybridization (CGH) is a powerful tool for detection of submicroscopic chromosome deletions and duplications. We describe two patients with mild mental retardation (MR) and de novo microdeletions of 17q11.2q12. Although the deletions did not involve the neurofibromatosis type 1 (NF1) gene, they overlap with long-range deletions of the NF1 region which have been encountered in a small group of NF1 patients with more severe MR. Given the overlap of the deletions in our two patients with the large-sized NF1 microdeletions but not with the more frequent and smaller NF1 deletions, we hypothesize that more than one gene in the 17q11.2q12 region may be involved in MR. We discuss candidate genes for MR within this interval that was precisely defined through array-CGH analysis.

Identification of proximal 1p36 deletions using array-CGH: a possible new syndrome

Monosomy 1p36 is the most common terminal deletion syndrome with an estimated occurrence of 1:5000 live births. Typically, the deletions span <10 Mb of 1pter-1p36.23 and result in mental retardation, developmental delay, sensorineural hearing loss, seizures, cardiomyopathy and cardiovascular malformations, and distinct facies including large anterior fontanel, deep-set eyes, straight eyebrows, flat nasal bridge, asymmetric ears, and pointed chin. We report five patients with 'atypical' proximal interstitial deletions from 1p36.23-1p36.11 using array-comparative genomic hybridization. Four patients carry large overlapping deletions of approximately 9.38-14.69 Mb in size, and one patient carries a small 2.97 Mb deletion. Interestingly, these patients manifest many clinical characteristics that are different from those seen in 'classical' monosomy 1p36 syndrome. The clinical presentation in our patients included: pre- and post-natal growth deficiency (mostly post-natal), feeding difficulties, seizures, developmental delay, cardiovascular malformations, microcephaly, limb anomalies, and dysmorphic features including frontal and parietal bossing, abnormally shaped and posteriorly rotated ears, hypertelorism, arched eyebrows, and prominent and broad nose. Most children also displayed hirsutism. Based on the analysis of the clinical and molecular data from our patients and those reported in the literature, we suggest that this chromosomal abnormality may constitute yet another deletion syndrome distinct from the classical distal 1p36 deletion syndrome.

Array-based comparative genomic hybridization facilitates identification of breakpoints of a novel der(1)t(1;18)(p36.3;q23)dn in a child presenting with mental retardation

Monosomy of distal 1p36 represents the most common terminal deletion in humans and results in one of the most frequently diagnosed mental retardation syndromes. This deletion is considered a contiguous gene deletion syndrome, and has been shown to vary in deletion sizes that contribute to the spectrum of phenotypic anomalies seen in patients with monosomy 1p36. We report on an 8-year-old female with characteristics of the monosomy 1p36 syndrome who demonstrated a novel der(1)t(1;18)(p36.3;q23). Initial G-banded karyotype analysis revealed a deleted chromosome 1, with a breakpoint within 1p36.3. Subsequent FISH and array-based comparative genomic hybridization not only confirmed and partially characterized the deletion of chromosome 1p36.3, but also uncovered distal trisomy for 18q23. In this patient, the duplicated 18q23 is translocated onto the deleted 1p36.3 region, suggesting telomere capture. Molecular characterization of this novel der(1)t(1;18)(p36.3;q23), guided by our clinical array-comparative genomic hybridization, demonstrated a 3.2 Mb terminal deletion of chromosome 1p36.3 and a 200 kb duplication of 18q23 onto the deleted 1p36.3, presumably stabilizing the deleted chromosome 1. DNA sequence analysis around the breakpoints demonstrated no homology, and therefore this telomere capture of distal 18q is apparently the result of a non-homologous recombination. Partial trisomy for 18q23 has not been previously reported. The importance of mapping the breakpoints of all balanced and unbalanced translocations found in the clinical laboratory, when phenotypic abnormalities are found, is discussed.