Phase I clinical study of oral olaparib in pediatric patients with refractory solid tumors: study protocol

DNA Ligase 4 Contributes to Cell Proliferation against DNA-PK Inhibition in MYCN-Amplified Neuroblastoma IMR32 Cells

Identifying the vulnerability of altered DNA repair machinery that displays synthetic lethality with MYCN amplification is a therapeutic rationale in unfavourable neuroblastoma. However, none of the inhibitors for DNA repair proteins are established as standard therapy in neuroblastoma. Here, we investigated whether DNA-PK inhibitor (DNA-PKi) could inhibit the proliferation of spheroids derived from neuroblastomas of MYCN transgenic mice and MYCN-amplified neuroblastoma cell lines. DNA-PKi exhibited an inhibitory effect on the proliferation of MYCN-driven neuroblastoma spheroids, whereas variable sensitivity was observed in those cell lines. Among them, the accelerated proliferation of IMR32 cells was dependent on DNA ligase 4 (LIG4), which comprises the canonical non-homologous end-joining pathway of DNA repair. Notably, LIG4 was identified as one of the worst prognostic factors in patients with MYCN-amplified neuroblastomas. It may play complementary roles in DNA-PK deficiency, suggesting the therapeutic potential of LIG4 inhibition in combination with DNA-PKi for MYCN-amplified neuroblastomas to overcome resistance to multimodal therapy.

Italian Precision Medicine in Pediatric Oncology: Moving beyond Actionable Alterations

Neuroblastoma (NB) is the most common extracranial solid tumor encountered in childhood. Although there has been significant improvement in the outcomes of patients with high-risk disease, the prognosis for patients with metastatic relapse or refractory disease is poor. Hence, the clinical integration of genome sequencing into standard clinical practice is necessary in order to develop personalized therapy for children with relapsed or refractory disease. The PeRsonalizEdMEdicine (PREME) project focuses on the design of innovative therapeutic strategies for patients suffering from relapsed NB. We performed whole exome sequencing (WES) of patient-matched tumor-normal samples to identify genetic variants amenable to precision medicine. Specifically, two patients were studied (First case: a three-year-old male with early relapsed NB; Second case: a 20-year-old male who relapsed 10 years after the first diagnosis of NB). Results were reviewed by a multi-disciplinary molecular tumor board (MTB) and clinical reports were issued to the ordering physician. WES revealed the mutation c.G320C in the CUL4A gene in case 1 and the mutation c.A484G in the PSMC2 gene in case 2. Both patients were treated according to these actionable alterations, with promising results. The effective treatment of NB is one of the main challenges in pediatric oncology. In the era of precision medicine, the need to design new therapeutic strategies for NB is fundamental. Our results demonstrate the feasibility of incorporating clinical WES into pediatric oncology practice.

LncRNA H19 Impairs Chemo and Radiotherapy in Tumorigenesis

Various treatments based on drug administration and radiotherapy have been devoted to preventing, palliating, and defeating cancer, showing high efficiency against the progression of this disease. Recently, in this process, malignant cells have been found which are capable of triggering specific molecular mechanisms against current treatments, with negative consequences in the prognosis of the disease. It is therefore fundamental to understand the underlying mechanisms, including the genes—and their signaling pathway regulators—involved in the process, in order to fight tumor cells. Long non-coding RNAs, H19 in particular, have been revealed as powerful protective factors in various types of cancer. However, they have also evidenced their oncogenic role in multiple carcinomas, enhancing tumor cell proliferation, migration, and invasion. In this review, we analyze the role of lncRNA H19 impairing chemo and radiotherapy in tumorigenesis, including breast cancer, lung adenocarcinoma, glioma, and colorectal carcinoma.

First phase 1 clinical study of olaparib in pediatric patients with refractory solid tumors

BACKGROUND

The survival of patients with high-risk, refractory, relapsed, or metastatic solid tumors remains dismal. A poly(ADP-ribose) polymerase (PARP) inhibitor could be effective for the treatment of pediatric solid tumors with defective homologous recombination.

METHODS

This open-label, multicenter phase 1 clinical trial evaluated the safety, tolerability, and efficacy of olaparib, a PARP inhibitor, in pediatric patients with refractory solid tumors to recommend a dose for Phase 2 trials. Olaparib (62.5, 125, and 187.5 mg/m² twice daily) was administered orally every day (1 cycle = 28 days) using a standard 3 + 3 dose-escalation design. Patients aged 3-18 years with recurrent pediatric solid tumors were eligible. Pharmacokinetic and pharmacodynamic analyses were performed.

RESULTS

Fifteen patients were enrolled and received olaparib monotherapy, which was well tolerated. The recommended phase 2 dose for daily administration was 187.5 mg/m² twice daily. Pharmacokinetics were dose proportional. The area under the concentration-time curve from 0 to 12 h and the peak plasma concentration for 187.5 mg/m² twice daily in children were comparable to previous data obtained in a 200-mg, twice-daily cohort and lower than those in the 300-mg twice-daily cohort in adults. Pharmacodynamic studies demonstrated substantial inhibition of PARP activity. Two partial responses were observed in patients with Wilms tumor and neuroblastoma.

CONCLUSIONS

This report is the first clinical trial to describe the use of a PARP inhibitor as monotherapy in children. Olaparib was well tolerated, with preliminary antitumor responses observed in DNA damage response-defective pediatric tumors.

LAY SUMMARY

This Phase 1 trial evaluated the efficacy and safety of olaparib in patients with refractory childhood solid tumors. Olaparib was well tolerated, achieving objective response in 2/15 patients. The DNA damage response was attenuated in nearly one-half of advanced neuroblastoma patients, demonstrating the utility of the PARP inhibitor. The results support further investigation of olaparib as a new treatment for DNA damage-response or repair-defective pediatric cancers.

A combination of PARP and CHK1 inhibitors efficiently antagonizes MYCN-driven tumors

MYCN drives aggressive behavior and refractoriness to chemotherapy, in several tumors. Since MYCN inactivation in clinical settings is not achievable, alternative vulnerabilities of MYCN-driven tumors need to be explored to identify more effective and less toxic therapies. We previously demonstrated that PARP inhibitors enhance MYCN-induced replication stress and promote mitotic catastrophe, counteracted by CHK1. Here, we showed that PARP and CHK1 inhibitors synergized to induce death in neuroblastoma cells and in primary cultures of SHH-dependent medulloblastoma, their combination being more effective in MYCN amplified and MYCN overexpressing cells compared to MYCN non-amplified cells. Although the MYCN amplified IMR-32 cell line carrying the p.Val2716Ala ATM mutation showed the highest sensitivity to the drug combination, this was not related to ATM status, as indicated by CRISPR/Cas9-based correction of the mutation. Suboptimal doses of the CHK1 inhibitor MK-8776 plus the PARP inhibitor olaparib led to a MYCN-dependent accumulation of DNA damage and cell death in vitro and significantly reduced the growth of four in vivo models of MYCN-driven tumors, without major toxicities. Our data highlight the combination of PARP and CHK1 inhibitors as a new potential chemo-free strategy to treat MYCN-driven tumors, which might be promptly translated into clinical trials.

Germline ATM mutation and somatic PIK3CA and BCOR mutations found in an infant with aggressive orbital embryonal rhabdomyosarcoma

Purpose

To report a case of aggressive infantile orbital embryonal rhabdomyosarcoma harboring germline ATM mutation and 2 somatic mutations as revealed by next-generation sequencing and the potential application for personalized therapy.

Observations

A 7-month-old male developed a rapidly progressive left proptosis over 6 weeks due to a large medial orbital mass. Biopsy revealed embryonal rhabdomyosarcoma. After the first cycle of chemotherapy, re-imaging showed interval tumor enlargement with intracranial extension. Craniotomy, combined with orbital exenteration, was performed. Tumor specimens and blood samples were sent for 596 gene DNA sequencing panels with RNA-sequencing focused on actionable mutations as well as gene fusion detection. Sequencing revealed 3 clinically relevant mutations: a germline ATM loss-of-function (LOF) mutation, a somatic PIK3CA gain-of-function mutation, and a somatic BCOR LOF mutation. No chromosomal translocation was detected. Workup for metastasis was positive for bone marrow involvement. Despite standard high-dose adjuvant chemotherapy in combination with radiation therapy, the patient died 10 months later with metastatic diseases.

Conclusions and importance

This case highlights an aggressive form of embryonal rhabdomyosarcoma in an infantile orbit. The presence of germline mutation may explain the increased chemo-resistance and adverse prognosis, and may be used as the target for genomic-directed therapy.

Veliparib Is an Effective Radiosensitizing Agent in a Preclinical Model of Medulloblastoma

Medulloblastoma is the most common malignant childhood brain tumor, and 5-year overall survival rates are as low as 40% depending on molecular subtype, with new therapies critically important. As radiotherapy and chemotherapy act through the induction of DNA damage, the sensitization of cancer cells through the inhibition of DNA damage repair pathways is a potential therapeutic strategy. The poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib was assessed for its ability to augment the cellular response to radiation-induced DNA damage in human medulloblastoma cells. DNA repair following irradiation was assessed using the alkaline comet assay, with veliparib inhibiting the rate of DNA repair. Veliparib treatment also increased the number of γH2AX foci in cells treated with radiation, and analysis of downstream pathways indicated persistent activation of the DNA damage response pathway. Clonogenicity assays demonstrated that veliparib effectively inhibited the colony-forming capacity of medulloblastoma cells, both as a single agent and in combination with irradiation. These data were then validated in vivo using an orthotopic implant model of medulloblastoma. Mice harboring intracranial D425 medulloblastoma xenografts were treated with vehicle, veliparib, 18 Gy multifractionated craniospinal irradiation (CSI), or veliparib combined with 18 Gy CSI. Animals treated with combination therapy exhibited reduced tumor growth rates concomitant with increased intra-tumoral apoptosis observed by immunohistochemistry. Kaplan–Meier analyses revealed a statistically significant increase in survival with combination therapy compared to CSI alone. In summary, PARP inhibition enhanced radiation-induced cytotoxicity of medulloblastoma cells; thus, veliparib or other brain-penetrant PARP inhibitors are potential radiosensitizing agents for the treatment of medulloblastoma.

Poly (ADP-ribose) polymerase inhibitor exposure reduces ovarian reserve followed by dysfunction in granulosa cells

The use of poly (ADP-ribose) polymerase (PARP) inhibitors is expected to increase, but their effect on fertility is still unclear. The aim of this study was to investigate the effect of PARP inhibitors on ovarian function. In an in vitro study, cultures of ovaries and granulosa cells (GCs) exposed to the PARP inhibitor olaparib were evaluated by real-time RT-PCR, histological study, and hormone assays. In an in vivo study, mice were administered olaparib orally and evaluated via in vitro fertilization (IVF), follicle count, immunohistochemical staining, and real-time RT-PCR. In vitro, the gene expression of GC markers decreased in the olaparib-treated group. Olaparib also negatively affected estradiol production and the expression of GC markers in cultured GCs, with abnormal morphology of GCs observed in the treated group. The follicle number indicated depletion of follicles due to atretic changes in the treatment group, both in vitro and in vivo. Also, olaparib reduced the number of retrieved oocytes and the fertilization rate of IVF, but they recovered after 3 weeks of cessation. Our results indicate that olaparib is toxic to ovaries.

Mini-Review on Targeted Treatment of Desmoplastic Small Round Cell Tumor

Desmoplastic small round cell tumor (DSRCT) is a devastating disease which most commonly affects adolescents, with a male predominance. Despite the best multimodality treatment efforts, most patients will ultimately not survive more than 3-5 years after diagnosis. Some research trials in soft-tissue sarcoma and Ewing sarcoma include DSRCT patients but few studies have been tailored to the specific clinical needs and underlying cytogenetic abnormalities characterizing this disease such as the typical EWSR1-WT1 gene fusion. Downstream activation of EWSR1-WT1 gene fusion includes signaling pathways of platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and insulin growth factor (IGF)-1. Other biological pathways that are activated and expressed in DSRCT cells include endothelial growth factor receptor (EGFR), androgen receptor pathway, c-KIT, MET, and transforming growth factor (TGF) beta. Investigation of somatic mutations, copy number alterations (CNA), and chromosomes in DSRCT samples suggests that deregulation of mesenchymal-epithelial reverse transition (MErT)/epithelial-mesenchymal transition (EMT) and DNA damage repair (DDR) may be important in DSRCT. This mini review looks at known druggable targets in DSRCT and existing clinical evidence for targeted treatments, particularly multityrosine kinase inhibitors such as pazopanib, imatinib, and sorafenib alone or in combination with other agents such as mTOR (mammalian target of rapamycin) inhibitors. The aim is to increase shared knowledge about current available treatments and identify gaps in research to further efforts toward clinical development of targeted agents.