Prenatal diagnosis (or lack thereof) of arthrogryposis multiplex congenita and its impact on the perinatal experience of parents: A retrospective survey

OBJECTIVE

To examine parental experiences during pregnancies affected by Arthrogryposis Multiplex Congenita (AMC) by identifying commonalities, risk factors, and areas for improvement in detection rates, care protocols, and patient experience.

STUDY DESIGN

An online survey was distributed via AMC support groups on Facebook. Topics included demographics, risk factors, parental recall of sonographic findings, delivery characteristics and neonatal findings. Responses were divided into antenatally detected cases (ADCs) and postnatally detected cases (PDCs). Quantitative responses were analyzed with the Fisher exact test. Qualitative data were analyzed with thematic analysis.

RESULTS

The antenatal detection rate of arthrogryposis was 37%. Decreased fetal movement was reported by 53% and early bleeding by 21%. Sonographic findings in ADCs included clubfoot (83%), clenched hand (51%), decreased fetal movement (50%), elbow contracture (51%), and knee contracture (46%). Among ADCs, 29% delivered vaginally and 71% delivered by cesarean versus PDCs (44% vaginal, 56% cesarean). Neonatal intensive care unit admission rate was 63%. Bone fracture occurred in 9%. Detection led to a planned change in delivery mode in 33% and location in 50%. Among ADCs, 17% felt their concerns were not adequately addressed versus 43% of PDCs.

CONCLUSIONS

Antenatal detection of arthrogryposis was low. We propose enhanced screening criteria to aid prenatal diagnosis and promote utilization of more robust practice guidelines.

CDK4/6 inhibitors target SMARCA4-determined cyclin D1 deficiency in hypercalcemic small cell carcinoma of the ovary

Inactivating mutations in SMARCA4 (BRG1), a key SWI/SNF chromatin remodelling gene, underlie small cell carcinoma of the ovary, hypercalcemic type (SCCOHT). To reveal its druggable vulnerabilities, we perform kinase-focused RNAi screens and uncover that SMARCA4-deficient SCCOHT cells are highly sensitive to the inhibition of cyclin-dependent kinase 4/6 (CDK4/6). SMARCA4 loss causes profound downregulation of cyclin D1, which limits CDK4/6 kinase activity in SCCOHT cells and leads to in vitro and in vivo susceptibility to CDK4/6 inhibitors. SCCOHT patient tumors are deficient in cyclin D1 yet retain the retinoblastoma-proficient/p16INK4a-deficient profile associated with positive responses to CDK4/6 inhibitors. Thus, our findings indicate that CDK4/6 inhibitors, approved for a breast cancer subtype addicted to CDK4/6 activation, could be repurposed to treat SCCOHT. Moreover, our study suggests a novel paradigm whereby critically low oncogene levels, caused by loss of a driver tumor suppressor, may also be exploited therapeutically.

Abstract 335: Variable off-target effects of clinically advanced PARP inhibitors

High-grade serous ovarian carcinoma (HGSOC) is the most common subtype of ovarian cancer with low 5-year survival rates. Inhibitors of poly (ADP-ribose) polymerase (PARP) are promising novel agents that uniquely target HGSOCs with DNA repair deficiencies. The majority of patients with DNA repair proficient HGSOCs do not respond to PARP inhibitor monotherapy, highlighting the need for novel treatment approaches for these women. The goal of this study was to expand the patient population that could benefit from PARP inhibition by identifying the off-target effects that are favorable in combination with CHK1 inhibitors among the five most clinically advanced PARP inhibitors.

Cell cycle and western blot analysis revealed that the four most potent PARP trappers (rucaparib, olaparib, niraparib, and talazoparib) have a strong effect on the cell cycle. The PARP trappers in particular activated CHK1 through phosphorylation at the serine 345 residue, decreased total protein levels of CDC25C, and arrested cells in the S/G2 phase of the cell cycle. These results were not observed after treatment with veliparib, the least potent PARP trapper. We created phospo-CHK1 mutants to confirm CHK1 activation at serine 345 and to further investigate whether potent PARP trappers activate CHK1 on serine 317, another residue that is also phosphorylated in response to replication stress. The data suggest that PARP trappers activate CHK1 at both the serine 317 and 345 phosphorylation sites.

Next, we examined whether PARP inhibition-induced activation of CHK1 is a determinant of synergy between PARP and CHK1 inhibitors. We exposed one of our established BRCA wild-type, TP53 mutant HGSOC patient-derived xenograft models to a PARP1 inhibitor (veliparib or talazoparib) or to the CHK1 inhibitor (MK-8776) or a combination of PARP and CHK1 inhibitors. CHK1 inhibition slightly increased sensitivity to talazoparib compared to single agent therapy. However, the tumor volume was significantly reduced by the combination of CHK1 inhibition and veliparib treatment compared to either single agent alone. This study suggests that there are off-target cell cycle effects that vary among the five most clinically-advanced PARP inhibitors that likely influence the response to combinatorial treatment. We propose the use of PARP and CHK1 inhibition as a strategy for HGSOC patients who would otherwise have minimal benefit to PARP inhibitor monotherapy.

Citation Format: Monica E. Wielgos, Jay Patibandla, Michelle Firlit, Elke Van Oudenhove, Paulina Cybulska, Petar Jelinic, Douglas A. Levine. Variable off-target effects of clinically advanced PARP inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 335.