PARP inhibitors alone and in combination with other biological agents in homologous recombination deficient epithelial ovarian cancer: From the basic research to the clinic

Inhibiting PRMT5 induces DNA damage and increases anti-proliferative activity of Niraparib, a PARP inhibitor, in models of breast and ovarian cancer

BACKGROUND

Inhibitors of Poly (ADP-Ribose) Polymerases (PARP) provide clinical benefit to patients with breast and ovarian cancers, by compromising the DNA repair activity of cancer cells. Although these agents extend progression-free survival in many patients, responses can be short lived with many patients ultimately progressing. Identification of combination partners that increase dependence of cancer cells to the DNA repair activity of PARPs may represent a strategy to increase the utility of PARP inhibitors. Protein arginine methyltransferase 5 (PRMT5) regulates DNA damage response pathways through splicing and protein modification, and inhibitors of PRMT5 have recently entered clinical trials.

METHODS

The effect of PRMT5 inhibition on the levels of DNA damage and repair markers including γH2AX, RAD51, and 53BP1 was determined using high content immunofluorescent imaging. The anti-proliferative activity of the combination of PRMT5 and PARP inhibitors was evaluated using in vitro models of breast and ovarian cancers using both cell lines and ex vivo patient derived xenografts. Finally, the combinations of PRMT5 and PARP inhibitors were evaluated in cell line xenograft models in vivo.

RESULTS

Inhibition of PRMT5 by GSK3326595 led to increased levels of markers of DNA damage. The addition of GSK3326595 to the PARP inhibitor, niraparib, resulted in increased growth inhibition of breast and ovarian cancer cell lines and patient derived spheroids. In vivo, the combination improved the partial effects on tumor growth inhibition achieved by either single agent, producing complete tumor stasis and regression.

CONCLUSION

These data demonstrate that inhibition of PRMT5 induced signatures of DNA damage in models of breast and ovarian cancer. Furthermore, combination with the PARP inhibitor, Niraparib, resulted in increased anti-tumor activity in vitro and in vivo. Overall, these data suggest inhibition of PRMT5 as a mechanism to broaden and enhance the clinical application of PARP inhibitors.

Studying the DNA damage response pathway in hematopoietic canine cancer cell lines, a necessary step for finding targets to generate new therapies to treat cancer in dogs

Background

Dogs present a significant opportunity for studies in comparative oncology. However, the study of cancer biology phenomena in canine cells is currently limited by restricted availability of validated antibody reagents and techniques. Here, we provide an initial characterization of the expression and activity of key components of the DNA Damage Response (DDR) in a panel of hematopoietic canine cancer cell lines, with the use of commercially available antibody reagents.

Materials and methods

The techniques used for this validation analysis were western blot, qPCR, and DNA combing assay.

Results

Substantial variations in both the basal expression (ATR, Claspin, Chk1, and Rad51) and agonist-induced activation (p-Chk1) of DDR components were observed in canine cancer cell lines. The expression was stronger in the CLBL-1 (B-cell lymphoma) and CLB70 (B-cell chronic lymphocytic leukemia) cell lines than in the GL-1 (B-cell leukemia) cell line, but the biological significance of these differences requires further investigation. We also validated methodologies for quantifying DNA replication dynamics in hematopoietic canine cancer cell lines, and found that the GL-1 cell line presented a higher replication fork speed than the CLBL-1 cell line, but that both showed a tendency to replication fork asymmetry.

Conclusion

These findings will inform future studies on cancer biology, which will facilitate progress in developing novel anticancer therapies for canine patients. They can also provide new knowledge in human oncology.

Immune Checkpoint Inhibitors Combined with Targeted Therapy: The Recent Advances and Future Potentials

Immune checkpoint inhibitors (ICIs) have revolutionized the therapeutic landscape of cancer and have been widely approved for use in the treatment of diverse solid tumors. Targeted therapy has been an essential part of cancer treatment for decades, and in most cases, a special drug target is required. Numerous studies have confirmed the synergistic effect of combining ICIs with targeted therapy. For example, triple therapy of PD-L1 inhibitor atezolizumab plus BRAF inhibitor vemurafenib and MEK inhibitor cobimetinib has been approved as the first-line treatment in advanced melanoma patients with BRAFV600 mutations. However, not all combinations of ICIs and targeted therapy work. Combining ICIs with EGFR inhibitors in non-small-cell lung cancer (NSCLC) with EGFR mutations only triggered toxicities and did not improve efficacy. Therefore, the efficacies of combinations of ICIs and different targeted agents are distinct. This review firstly and comprehensively covered the current status of studies on the combination of ICIs mainly referring to PD-1 and PD-L1 inhibitors and targeted drugs, including angiogenesis inhibitors, EGFR/HER2 inhibitors, PARP inhibitors and MAPK/ERK signaling pathway inhibitors, in the treatment of solid tumors. We discussed the underlying mechanisms, clinical efficacies, side effects, and potential predictive biomarkers to give an integrated view of the combination strategy and provide perspectives for future directions in solid tumors.

BRCA gene amplification in primary peritoneal high-grade serous carcinoma patient with intrinsic resistance to platinum treatment: a case report

Platinum-based chemotherapy is the standard chemotherapy for high grade serous ovarian cancer and primary peritoneal high-grade serous carcinoma. PARP inhibitors have changed the paradigm of the treatment in platinum-sensitive ovarian cancers and primary peritoneal high-grade serous carcinoma with BRCA1/2 mutation or homologous recombination deficiency (HRD). Platinum-resistant ovarian and primary peritoneal high-grade serous carcinoma have a lower chance to treat and have worse outcomes. We described a case of patient with a platinum resistant primary peritoneal high-grade serous carcinoma with a rare somatic BRCA2 amplification. There are no guidelines for the treatment of ovarian cancer or primary peritoneal high-grade serous carcinoma with BRCA2 amplification. BRCA2 amplification could result in extreme homologous recombination repair (HRR) pathway efficiency and in less platinum sensitivity, which could be a molecular signature for platinum resistance. Free platinum chemotherapy regimens could be more effective in cases with BRCA2 amplification. Further studies are necessary to establish better approaches and strategies for oncological management and treatment in BRCA2 amplification high grade ovarian cancer and primary peritoneal high-grade serous carcinoma.

The Poly (ADP-ribose) polymerase inhibitor olaparib and pan-ErbB inhibitor neratinib are highly synergistic in HER2 overexpressing epithelial ovarian carcinoma in vitro and in vivo

INTRODUCTION

Ovarian cancer (OC) is associated with the highest gynecologic cancer mortality. The development of novel, effective combinations of targeted therapeutics remains an unmet medical need. We evaluated the preclinical efficacy of the Poly (ADP-ribose) polymerase (PARP) inhibitor (olaparib) and the pan-ErbB inhibitor (neratinib) as single agents and in combination in ovarian cancer cell lines and xenografts with variable HER2 expression.

METHODS

In vitro cell viability with olaparib, neratinib, and their combination was assessed using flow-cytometry based assays against a panel of OC primary cell lines with variable HER2 expression. Immunoblotting experiments were performed to elucidate the mechanism of activity and synergism. The in vivo antitumor activity of the olaparib/neratinib combination versus single agents was tested in HER2 positive xenograft OC models.

RESULTS

HER2 + OC cell lines demonstrated higher sensitivity to olaparib and neratinib when compared to HER2 negative tumors (i.e., IC50: 2.06 ± 0.33 μM vs. 39.28 ± 30.51 μM, p = 0.0035 for olaparib and 19.42 ± 2.63 nM vs. 235.0 ± 165.0 nM, p = 0.0035 for neratinib). The combination of olaparib with neratinib was more potent when compared to single-agent olaparib or neratinib both in vitro and in vivo, and demonstrated synergy in all primary HER2 + OC models. Western blot experiments showed neratinib decreased pHER2/neu while increased Poly(ADP-ribose) (PAR) enzymatic activity; olaparib increased pHER2/Neu expression and blocked PAR activatio. Olaparib/neratinib in combination decreased both pHER2/Neu as well as PAR activation.

CONCLUSION

The combination of olaparib and neratinib is synergistic and endowed with remarkable preclinical activity against HER2+ ovarian cancers. This combination may represent a novel therapeutic option for ovarian cancer patients with HER2+, homologous recombination-proficient tumors resistant to chemotherapy.

Homologous Recombination Deficiency in Ovarian Cancer: from the Biological Rationale to Current Diagnostic Approaches

The inability to efficiently repair DNA double-strand breaks using the homologous recombination repair pathway is defined as homologous recombination deficiency (HRD). This molecular phenotype represents a positive predictive biomarker for the clinical use of poly (adenosine diphosphate [ADP]-ribose) polymerase inhibitors and platinum-based chemotherapy in ovarian cancers. However, HRD is a complex genomic signature, and different methods of analysis have been developed to introduce HRD testing in the clinical setting. This review describes the technical aspects and challenges related to HRD testing in ovarian cancer and outlines the potential pitfalls and challenges that can be encountered in HRD diagnostics.

The Molecular Mechanisms of Actions, Effects, and Clinical Implications of PARP Inhibitors in Epithelial Ovarian Cancers: A Systematic Review

Ovarian cancer is the most lethal gynecologic malignancy in the United States. Some patients affected by ovarian cancers often present genome instability with one or more of the defects in DNA repair pathways, particularly in homologous recombination (HR), which is strictly linked to mutations in breast cancer susceptibility gene 1 (BRCA 1) or breast cancer susceptibility gene 2 (BRCA 2). The treatment of ovarian cancer remains a challenge, and the majority of patients with advanced-stage ovarian cancers experience relapse and require additional treatment despite initial therapy, including optimal cytoreductive surgery (CRS) and platinum-based chemotherapy. Targeted therapy at DNA repair genes has become a unique strategy to combat homologous recombination-deficient (HRD) cancers in recent years. Poly (ADP-ribose) polymerase (PARP), a family of proteins, plays an important role in DNA damage repair, genome stability, and apoptosis of cancer cells, especially in HRD cancers. PARP inhibitors (PARPi) have been reported to be highly effective and low-toxicity drugs that will tremendously benefit patients with HRD (i.e., BRCA 1/2 mutated) epithelial ovarian cancer (EOC) by blocking the DNA repair pathways and inducing apoptosis of cancer cells. PARP inhibitors compete with NAD⁺ at the catalytic domain (CAT) of PARP to block PARP catalytic activity and the formation of PAR polymers. These effects compromise the cellular ability to overcome DNA SSB damage. The process of HR, an essential error-free pathway to repair DNA DSBs during cell replication, will be blocked in the condition of BRCA 1/2 mutations. The PARP-associated HR pathway can also be partially interrupted by using PARP inhibitors. Grossly, PARP inhibitors have demonstrated some therapeutic benefits in many randomized phase II and III trials when combined with the standard CRS for advanced EOCs. However, similar to other chemotherapy agents, PARP inhibitors have different clinical indications and toxicity profiles and also face drug resistance, which has become a major challenge. In high-grade epithelial ovarian cancers, the cancer cells under hypoxia- or drug-induced stress have the capacity to become polyploidy giant cancer cells (PGCCs), which can survive the attack of chemotherapeutic agents and start endoreplication. These stem-like, self-renewing PGCCs generate mutations to alter the expression/function of kinases, p53, and stem cell markers, and diploid daughter cells can exhibit drug resistance and facilitate tumor growth and metastasis. In this review, we discuss the underlying molecular mechanisms of PARP inhibitors and the results from the clinical studies that investigated the effects of the FDA-approved PARP inhibitors olaparib, rucaparib, and niraparib. We also review the current research progress on PARP inhibitors, their safety, and their combined usage with antiangiogenic agents. Nevertheless, many unknown aspects of PARP inhibitors, including detailed mechanisms of actions, along with the effectiveness and safety of the treatment of EOCs, warrant further investigation.

Long‑term survival of a BRCA2 mutation carrier following second ovarian cancer relapse using PARPi therapy: A case report

BRCA1/2 mutation carriers have lifelong increased risks of developing breast and ovarian cancer. Due to the lack of efficient ovarian cancer screening, patients mainly present when the tumors are at an advanced stage, and the long-term survival is poor. The application of poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) has been used in personalized cancer treatment. Specific strategies to improve the outcome of patients are available and mainly include targeting of BRCA1 or BRCA2 mutations. The aim of the present study was to report the case of a 67-year old BRCA2 mutation carrier, who was enrolled in 2010 in one of the first PARPi studies (ICEBERG2). The patient exhibited second ovarian cancer (OC) relapse following a platinum-free interval of 5 months. The third-line treatment with olaparib monotherapy was initiated in January 2011, without prior surgery or chemotherapy, and achieved a persistent response. The patient demonstrated an unprecedented long-term survival of >9 years under PARPi monotherapy after the second relapse of OC. The data of the present case report support the use of PARPi as a well-tolerated and effective long-term treatment, even for patients with unfavourable prognostic characteristics, such as platinum resistance, without immediately preceding optimal cytoreduction. However, further studies are required to provide more insight into the selection of patients for favourable maintenance treatment.

Homologous Recombination Deficiency in Ovarian, Breast, Colorectal, Pancreatic, Non-Small Cell Lung and Prostate Cancers, and the Mechanisms of Resistance to PARP Inhibitors

Homologous recombination (HR) is a highly conserved DNA repair mechanism that protects cells from exogenous and endogenous DNA damage. Breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) play an important role in the HR repair pathway by interacting with other DNA repair proteins such as Fanconi anemia (FA) proteins, ATM, RAD51, PALB2, MRE11A, RAD50, and NBN. These pathways are frequently aberrant in cancer, leading to the accumulation of DNA damage and genomic instability known as homologous recombination deficiency (HRD). HRD can be caused by chromosomal and subchromosomal aberrations, as well as by epigenetic inactivation of tumor suppressor gene promoters. Deficiency in one or more HR genes increases the risk of many malignancies. Another conserved mechanism involved in the repair of DNA single-strand breaks (SSBs) is base excision repair, in which poly (ADP-ribose) polymerase (PARP) enzymes play an important role. PARP inhibitors (PARPIs) convert SSBs to more cytotoxic double-strand breaks, which are repaired in HR-proficient cells, but remain unrepaired in HRD. The blockade of both HR and base excision repair pathways is the basis of PARPI therapy. The use of PARPIs can be expanded to sporadic cancers displaying the “BRCAness” phenotype. Although PARPIs are effective in many cancers, their efficacy is limited by the development of resistance. In this review, we summarize the prevalence of HRD due to mutation, loss of heterozygosity, and promoter hypermethylation of 35 DNA repair genes in ovarian, breast, colorectal, pancreatic, non-small cell lung cancer, and prostate cancer. The underlying mechanisms and strategies to overcome PARPI resistance are also discussed.

DNA Damage Response (DDR) proteins in canine cancer as potential research targets in comparative oncology

The DNA damage response (DDR) is a complex signal transduction network that is activated when endogenous or exogenous genotoxins damage or interfere with the replication of genomic DNA. Under such conditions, the DDR promotes DNA repair and ensures accurate replication and division of the genome. High levels of genomic instability are frequently observed in cancers and can stem from germline loss‐of‐function mutations in certain DDR genes, such as BRCA1, BRCA2, and p53, that form the basis of human cancer predisposition syndromes. In addition, mutation and/or aberrant expression of multiple DDR genes are frequently observed in sporadic human cancers. As a result, the DDR is considered to represent a viable target for cancer therapy in humans and a variety of strategies are under investigation. Cancer is also a significant cause of mortality in dogs, a species that offers certain advantages for experimental oncology. Domestic dogs present numerous inbred lines, many of which display predisposition to specific forms of cancer and the study of which may provide insight into the biological basis of this susceptibility. In addition, clinical trials are possible in dogs and may lead to therapeutic insights that could ultimately be extended to humans. Here we review what is known specifically about the DDR in dogs and discuss how this knowledge could be extended and exploited to advance experimental oncology in this species.

Update on Poly ADP-Ribose Polymerase Inhibitors in Ovarian Cancer With Non-BRCA Mutations

Poly ADP-ribose polymerase inhibitor (PARPi) has become an important maintenance therapy for ovarian cancer after surgery and cytotoxic chemotherapy, which has changed the disease management model of ovarian cancer, greatly decreased the risk of recurrence, and made the prognosis of ovarian cancer better to certain extent. The three PARPis currently approved by the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of ovarian cancer are Olaparib, Niraparib and Rucaparib. With the incremental results from new clinical trials, the applicable population of PARPi for ovarian cancer have expanded to population with non-BRCA mutations. Although BRCA mutated population are still the main beneficiaries of PARPi, recent clinical trials indicated PARPis' therapeutic potential in non-BRCA mutated population, especially in homologous recombination repair deficiency (HRD) positive population. However, lack of unified HRD status detection method poses a challenge for the accurate selection of PARPi beneficiaries. The reversal of homologous recombination (HR) function during the treatment will not only cause resistance to PARPis, but also reduce the accuracy of the current method to determine HRD status. Therefore, the development of reliable HRD status detection methods to determine the beneficiary population, as well as rational combination treatment are warranted. This review mainly summarizes the latest clinical trial results and combination treatment of PARPis in ovarian cancer with non-BRCA mutations, and discusses the application prospects, including optimizing combination therapy against drug resistance, developing unified and accurate HRD status detection methods for patient selection and stratification. This review further poses an interesting topic: the efficacy and safety in patients retreated with PARPis after previous PARPi treatment---"PARPi after PARPi".

Ovarian Cancer in the Era of Immune Checkpoint Inhibitors: State of the Art and Future Perspectives

BACKGROUND

Ovarian cancer (OC) represents the eighth most common cancer and the fifth leading cause of cancer-related deaths among the female population. In an advanced setting, chemotherapy represents the first-choice treatment, despite a high recurrence rate. In the last ten years, immunotherapy based on immune checkpoint inhibitors (ICIs) has profoundly modified the therapeutic scenario of many solid tumors. We sought to summarize the main findings regarding the clinical use of ICIs in OC.

METHODS

We searched PubMed, Embase, and Cochrane Databases, and conference abstracts from international congresses (such as ASCO, ESMO, SGO) for clinical trials, focusing on ICIs both as monotherapy and as combinations in the advanced OC.

RESULTS

20 studies were identified, of which 16 were phase I or II and 4 phase III trials. These trials used ICIs targeting PD1 (nivolumab, pembrolizumab), PD-L1 (avelumab, aterolizumab, durvalumab), and CTLA4 (ipilimumab, tremelimumab). There was no reported improvement in survival, and some trials were terminated early due to toxicity or lack of response. Combining ICIs with chemotherapy, anti-VEGF therapy, or PARP inhibitors improved response rates and survival in spite of a worse safety profile.

CONCLUSIONS

The identification of biomarkers with a predictive role for ICIs' efficacy is mandatory. Moreover, genomic and immune profiling of OC might lead to better treatment options and facilitate the design of tailored trials.

Recent advancements of antiangiogenic combination therapies in ovarian cancer

Ovarian cancer is a deadly malignancy with a growing therapeutic armamentarium, though achieving sustained benefit in the clinic remains largely elusive. Through biomarker and genetic analysis, several pathways of resistance and sensitivity to commonly used therapeutics have been identified, expanding the potential of identifying unique drug combinations and indicating new directions for improving clinical outcomes. Here, we review the mechanisms of angiogenic response and antiangiogenic therapy in ovarian cancer, as well as the interactions it exhibits with the immune and DNA damage response pathways. We discuss results from clinical trials examining the combinations of antiangiogenics, PARP inhibitors, and immune checkpoint inhibitors are also discussed, as well as several ongoing trials.

Molecular pathology of prostate cancer: a practical approach

While localised prostate cancer can be cured by local treatment, 'high-risk' prostate cancer often progresses to castration resistant disease and remains incurable with a dismal prognosis. In recent years, technical advances and development of novel methodologies have largely contributed to a better understanding of underlying molecular mechanisms that promote tumour growth and progression. Consecutively, novel therapeutic strategies for treatment of prostate cancer have emerged during the last decade, calling for the identification of predictive biomarkers. The concept of personalised medicine is to tailor treatment according to the specific tumour profile of an individual patient. Moreover, acquired molecular changes during tumour evolution and in response to therapy selection pressure require adapted predictive marker testing at different time points during the disease. In this setting, the pathologist plays a critical role in patient management and treatment selection. In this review, we provide a comprehensive overview of the current knowledge of molecular aspects of prostate cancer and their potential utility in the context of different therapeutic approaches. Furthermore, we discuss methods for molecular marker testing in routine clinical practice, with a focus on castration resistant prostate cancer.

Inhibition of DNA Repair in Cancer Therapy: Toward a Multi-Target Approach

Alterations in DNA repair pathways are one of the main drivers of cancer insurgence. Nevertheless, cancer cells are more susceptible to DNA damage than normal cells and they rely on specific functional repair pathways to survive. Thanks to advances in genome sequencing, we now have a better idea of which genes are mutated in specific cancers and this prompted the development of inhibitors targeting DNA repair players involved in pathways essential for cancer cells survival. Currently, the pivotal concept is that combining the inhibition of mechanisms on which cancer cells viability depends is the most promising way to treat tumorigenesis. Numerous inhibitors have been developed and for many of them, efficacy has been demonstrated either alone or in combination with chemo or radiotherapy. In this review, we will analyze the principal pathways involved in cell cycle checkpoint and DNA repair focusing on how their alterations could predispose to cancer, then we will explore the inhibitors developed or in development specifically targeting different proteins involved in each pathway, underscoring the rationale behind their usage and how their combination and/or exploitation as adjuvants to classic therapies could help in patients clinical outcome.

PARP inhibitors and epithelial ovarian cancer: Molecular mechanisms, clinical development and future prospective

Epithelial ovarian cancer (EOC) has a poor prognosis. Since the introduction of paclitaxel as antineoplastic agent >20 years ago, only a few phase III randomized trials have shown challenging data regarding different therapeutic options for facing its aggressive clinical course and granting active therapies to patients. Different studies have shown the utility of poly(ADP-ribose) polymerase (PARP) inhibitors in women with EOC with or without BRCA mutations, both germline and somatic. Three PARP inhibitors, olaparib, rucaparib and niraparib, have been recently approved by the Food and Drug Administration for clinical use in EOC patients, though with different clinical indications and profiles of toxicity, while two other molecules, veliparib and talazoparib, are still under clinical investigation. The aim of the present paper is to evaluate the current status of PARP inhibitors in terms of molecular activity, pharmacodynamic properties and clinical applications.

MacroH2A1 Regulation of Poly(ADP-Ribose) Synthesis and Stability Prevents Necrosis and Promotes DNA Repair

Through its ability to bind the ends of poly(ADP-ribose) (PAR) chains, the function of the histone variant macroH2A1.1, including its ability to regulate transcription, is coupled to PAR polymerases (PARPs). PARP1 also has a major role in DNA damage response (DDR) signaling, and our results show that macroH2A1 alters the kinetics of PAR accumulation following acute DNA damage by both suppressing PARP activity and simultaneously protecting PAR chains from degradation.

Through its ability to bind the ends of poly(ADP-ribose) (PAR) chains, the function of the histone variant macroH2A1.1, including its ability to regulate transcription, is coupled to PAR polymerases (PARPs). PARP1 also has a major role in DNA damage response (DDR) signaling, and our results show that macroH2A1 alters the kinetics of PAR accumulation following acute DNA damage by both suppressing PARP activity and simultaneously protecting PAR chains from degradation. In this way, we demonstrate that macroH2A1 prevents cellular NAD⁺ depletion, subsequently preventing necrotic cell death that would otherwise occur due to PARP overactivation. We also show that macroH2A1-dependent PAR stabilization promotes efficient repair of oxidative DNA damage. While the role of PAR in recruiting and regulating macrodomain-containing proteins has been established, our results demonstrate that, conversely, macrodomain-containing proteins, and specifically those containing macroH2A1, can regulate PARP1 function through a novel mechanism that promotes both survival and efficient repair during DNA damage response.

Germline mutations in Thai patients with nonmucinous epithelial ovarian cancer

BACKGROUND

Genetic testing is widely recommended for all epithelial ovarian cancer (EOC) patients. However, an increased probability of identifying germline mutations has been reported in selected patients with risk factors such as a family history or personal history of cancer and high-grade serous carcinoma (HGSC) subtype. HGSC has been reported to be the most common subtype of EOC worldwide (approximately 70%). However, this subtype is less prevalent in Thai patients (reported as only 20%). The difference in the distribution of various subtypes of EOC may reflect the incidence of germline mutations in Thai EOC patients.

AIM

To evaluate the frequencies of germline mutations in EOC patients and to compare the frequencies in those with and without clinical risk factors for hereditary ovarian cancer.

METHODS

This cross-sectional study included 112 nonmucinous EOC patients who underwent primary surgery at our tertiary care hospital. Clinical risk factors for hereditary ovarian cancer were defined as follows: Age below 40 years, a significant family history of cancer, synchronous ovarian and endometrial cancer, and HGSC. Comprehensive germline mutations were detected by next-generation sequencing.

RESULTS

Of a total of 112 patients, 82 (73.2%) patients had ≥ 1 risk factor and 30 (26.8%) patients had no risk factors. Germline mutations were detected in 26 patients: 20 (17.8%) patients had BRCA1/2 mutations, but 6 (5.4%) patients had mutations in other genes, including 1 in MLH1, 1 in MSH2, 1 in RAD51C, 2 in ATM and 1 in CDH1. Germline mutations were only detected in patients with risk factors (26 of 82, 31.7%), not in patients without risk factors (P < 0.001). A significant family history of cancer and HGSC were the only two significant risk factors associated with a higher proportion of germline mutations (56.3% vs 10% for those with and without a history of cancer, respectively, 40.8% vs 9.5% for those with and without HGSC). Germline BRCA mutations were detected in 38.8% of patients with HGSC but in only 1.6% of those with non-HGSC. An age below 40 years, personal history of breast cancer, and synchronous ovarian and endometrial cancer were not significant factors (14.3% vs 23.5%, 33.3% vs 21%, 22.2% vs 22.3%).

CONCLUSION

Approximately one-third of EOC patients with risk factors had germline mutations. Almost all germline BRCA mutations were found in patients with the HGSC subtype. Selected patients with HGSC and a family history of cancer should be initially considered for genetic analysis in Thailand.

PARP-1 activity (PAR) determines the sensitivity of cervical cancer to olaparib

OBJECTIVES

Cervical cancer (CC) remains a major health problem worldwide. Poly (adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors (PARPi) have emerged as a promising class of chemotherapeutics in ovarian cancer. We explored the preclinical in vitro and in vivo activity of olaparib against multiple primary whole exome sequenced (WES) CC cells lines and xenografts.

METHODS

Olaparib cell-cycle, apoptosis, homologous-recombination-deficiency (HRD), PARP trapping and cytotoxicity activity was evaluated against 9 primary CC cell lines in vitro. PARP and PAR expression were analyzed by Western blot assays. Finally, olaparib in vivo antitumor activity was tested against CC xenografts.

RESULTS

While none of the cell lines demonstrated HRD, three out of 9 (33.3%) primary CC cell lines showed strong PARylation activity and demonstrated high sensitivity to olaparib in vitro treatment (cutoff IC50 values < 2 μM, p = 0.0012). Olaparib suppressed CC cell growth through cell cycle arrest in the G2/M phase and caused apoptosis (p < 0.0001). Olaparib activity in CC involved both PARP enzyme inhibition and trapping. In vivo, olaparib significantly impaired CC xenografts tumor growth (p = 0.0017) and increased overall animal survival (p = 0.008).

CONCLUSIONS

A subset of CC primary cell lines is highly responsive to olaparib treatment in vitro and in vivo. High level of PARylation correlated with olaparib preclinical activity and may represent a useful biomarker for the identification of CC patients benefitting the most from PARPi.

Cytotoxicity and Differentiating Effect of the Poly(ADP-Ribose) Polymerase Inhibitor Olaparib in Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are highly heterogeneous myeloid diseases, characterized by frequent genetic/chromosomal aberrations. Olaparib is a potent, orally bioavailable poly(ADP-ribose) polymerase 1 (PARP1) inhibitor with acceptable toxicity profile, designed as targeted therapy for DNA repair defective tumors. Here, we investigated olaparib activity in primary cultures of bone marrow mononuclear cells collected from patients with MDS (n = 28). A single treatment with olaparib induced cytotoxic effects in most samples, with median IC₅₀ of 5.4 µM (2.0–24.8 µM), lower than plasma peak concentration reached in vivo. In addition, olaparib induced DNA damage as shown by a high proportion of γH2AX positive cells in samples with low IC₅₀s. Olaparib preferentially killed myeloid cells causing a significant reduction of blasts and promyelocytes, paralleled by an increase in metamyelocytes and mature granulocytes while sparing lymphocytes that are not part of the MDS clone. Consistently, flow cytometry analysis revealed a decrease of CD117+/CD123+ immature progenitors (p < 0.001) and induction of CD11b+/CD16+ (p < 0.001) and CD10+/CD15+ (p < 0.01) neutrophils. Morphological and immunophenotypic changes were associated with a dose-dependent increase of PU.1 and CEBPA transcription factors, which are drivers of granulocytic and monocytic differentiation. Moreover, the combination of olaparib with decitabine resulted in augmented cytotoxic and differentiating effects. Our data suggest that olaparib may have therapeutic potential in MDS patients.

A Dose Escalation Study of Trientine Plus Carboplatin and Pegylated Liposomal Doxorubicin in Women With a First Relapse of Epithelial Ovarian, Tubal, and Peritoneal Cancer Within 12 Months After Platinum-Based Chemotherapy

Background: Epithelial ovarian cancer (EOC) is the leading cause of gynecological cancer-related deaths worldwide. Preclinical studies found that copper-lowering agents could re-sensitize platinum-resistant cancer cells by enhancing the human copper transporter 1 (hCtr1)-mediated uptake of platinum. In the clinic, re-sensitization of platinum-resistance in relapsed EOC has been discovered by the application of trientine plus platinum (NCT01178112). However, no pharmacokinetic data of trientine has been reported in cancer patients.

Purpose: Our study aimed to explore the safety and activity of trientine combined with carboplatin and pegylated liposomal doxorubicin (PLD) in patients with EOC, tubal, and peritoneal cancer who experienced disease progression during platinum-based chemotherapy or showed relapse <12 months after completing first-line chemotherapy. Also, we aimed to demonstrate pharmacokinetic parameters and to discover potential biomarkers in our EOC patients.

Methods: In this dose escalation study, 18 Asian patients in six dosing cohorts received fixed doses of carboplatin (AUC 4) and PLD (LipoDox®, TTY Biopharm Co. Ltd., Taipei, Taiwan) (40 mg/m², day 1 per 4-week cycle), and escalated daily trientine doses (range: 300–1800 mg; initiated 7 days before the 1st combination cycle) according to a 3 + 3 design.

Results: No dose-limiting toxicity or treatment-related death was observed. Four patients (22.2%) developed grade 3 drug-related adverse events (AEs), whereas no grade 4 AEs were encountered. Anemia and grade 2 dizziness were the most common hematological toxicity and neurotoxicity, respectively. In a pharmacokinetics comparison with healthy volunteers in the literature, our patients achieved greater absorption after oral trientinem, and more rapid elimination of triethylenetetramine dihydrochloride at high doses. The clinical benefit rate was 33.3 and 50.0% in the platinum-resistant and the partially platinum-sensitive group, respectively. A high baseline serum iron level and low serum copper level might help differentiate subgroups of patients with different clinical responses. Nevertheless, no associations of the clinical response with the levels of serum hCtr1, ceruloplasmin, or copper were observed.

Conclusion: Combination therapy with carboplatin, trientine, and PLD was well-tolerated and safe. Our results encourage the development of a future phase II trial.

Clinical trial registration:ClinicalTrials.gov # NCT03480750.

Micellar Formulation of Talazoparib and Buparlisib for Enhanced DNA Damage in Breast Cancer Chemoradiotherapy

Chemoradiation is an effective combined modality therapeutic approach that utilizes principles of spatial cooperation to combat the adaptability associated with cancer and to potentially expand the therapeutic window. Optimal therapeutic efficacy requires intelligent selection and refinement of radiosynergistic pharmaceutical agents, enhanced delivery methods, and temporal consideration. Here, a monodisperse sub-20 nm mixed poloxamer micelle (MPM) system was developed to deliver hydrophobic drugs intravenously, in tandem with ionizing radiation. This report demonstrates in vitro synergy and enhanced radiosensitivity when two molecularly targeted DNA repair inhibitors, talazoparib and buparlisib, are encapsulated and combined with radiation in a 4T1 murine breast cancer model. Evaluation of in vivo biodistribution and toxicity exhibited no reduction in particle accumulation upon radiation and a lack of both acute and chronic toxicities. In vivo efficacy studies suggested the promise of combining talazoparib, buparlisib, and radiation to enhance survival and control tumor growth. Tissue analysis suggests enhanced DNA damage leading to apoptosis, thus increasing efficacy. These findings highlight the challenges associated with utilizing clinically relevant inclusion criteria and treatment protocols because complete tumor regression and extended survival were masked by an aggressively metastasizing model. As with clinical treatment regimens, the findings here establish a need for further optimization of this multimodal platform.

Pharmacologic characterization of fluzoparib, a novel poly(ADP-ribose) polymerase inhibitor undergoing clinical trials

Poly(ADP-ribose) polymerase (PARP) enzymes play an important role in repairing DNA damage and maintaining genomic stability. Olaparib, the first-in-class PARP inhibitor, has shown remarkable clinical benefits in the treatment of BRCA-mutated ovarian or breast cancer. However, the undesirable hematological toxicity and pharmacokinetic properties of olaparib limit its clinical application. Here, we report the first preclinical characterization of fluzoparib (code name: SHR-3162), a novel, potent, and orally available inhibitor of PARP. Fluzoparib potently inhibited PARP1 enzyme activity and induced DNA double-strand breaks, G₂ /M arrest, and apoptosis in homologous recombination repair (HR)-deficient cells. Fluzoparib preferentially inhibited the proliferation of HR-deficient cells and sensitized both HR-deficient and HR-proficient cells to cytotoxic drugs. Notably, fluzoparib showed good pharmacokinetic properties, favorable toxicity profile, and superior antitumor activity in HR-deficient xenografts models. Furthermore, fluzoparib in combination with apatinib or with apatinib plus paclitaxel elicited significantly improved antitumor responses without extra toxicity. Based on these findings, studies to evaluate the efficacy and safety of fluzoparib (phase II) and those two combinations (phase I) have been initiated. Taken together, our results implicate fluzoparib as a novel attractive PARP inhibitor.

Current strategies for the targeted treatment of high-grade serous epithelial ovarian cancer and relevance of BRCA mutational status

Epithelial ovarian cancer is the most lethal gynecologic malignancy. In most women, it is diagnosed at an advanced stage, which largely explains the poor prognosis of this malignancy. Germline mutations of the genes BRCA1 and BRCA2, which encode proteins essential for the repair of double-strand DNA breaks through homologous recombination, lead to increased cancer predisposition. BRCA mutations are present in approximately 14% of epithelial ovarian cancers. Somatic BRCA mutations have also been described. Current first-line treatment of high-grade epithelial ovarian cancer includes debulking surgery followed by combination chemotherapy, usually carboplatin and paclitaxel. Ovarian cancer is highly sensitive to chemotherapy, in particular to platinum drugs. Most patient will achieve remission with initial chemotherapy, but most will eventually experience disease recurrence. Targeted therapies, including the anti-angiogenic agent bevacizumab and oral poly (ADP-ribose) polymerase (PARP) inhibitors, have been recently approved for the treatment of ovarian cancer, based on the results from randomized clinical trials showing significant benefits in terms of progression-free survival, with acceptable tolerability and no detrimental effects on quality of life. Olaparib, the first PARP inhibitor to be granted approval, is currently indicated as maintenance monotherapy in ovarian cancer patients with relapsed disease and mutated BRCA who have achieved a complete or partial response to platinum-based chemotherapy. The analysis of BRCA mutational status has, therefore, also become crucial for therapeutic decisions. Such advances are making personalized treatment of ovarian cancer feasible. Here we briefly review treatments for platinum-sensitive, high-grade serous epithelial ovarian cancer that are currently available in Italy, with a focus on targeted therapies and the relevance of BRCA mutational analysis. Based on the evidence and on current guidelines, we propose strategies for the tailored treatment of patients with relapsed ovarian cancer that take into account BRCA mutational status and the treatment received in the first-line setting.

A Road Map to Personalizing Targeted Cancer Therapies Using Synthetic Lethality

Targeted therapies rely on the genetic and epigenetic status of the tumor cells and are seen as the most promising approach to treat cancer today. However, current targeted therapies focus on directly inhibiting those molecules that are altered in tumor cells. Unfortunately, targeting these molecules, even with specific inhibitors, is challenging as tumor cells rewire their genetic circuitry to eliminate genetic dependency on these targets. Here, we describe how synthetic lethality approaches can be used to identify genetic dependencies and develop personalized targeted therapies. We also discuss strategies to specifically target these genetic dependencies, using small molecule and biologic drugs.

Rucaparib in ovarian cancer: extending the use of PARP inhibitors in the recurrent disease

Rucaparib is a potent inhibitor of poly (ADP-ribose) polymerase (PARP) PARP1, PARP2 and PARP3, and to a lesser extent, PARP4, PARP10, PARP12, PARP15 and PARP16. Study 10 and ARIEL2 evaluated the use of rucaparib as treatment in patients with recurrent high-grade ovarian carcinoma and resulting in approval of rucaparib for patients with both germline and somatic BRCA mutation. Data from the Phase III trial ARIEL3 led to approval in platinum-sensitive disease as maintenance. This article reviews the efficacy, safety, pharmacokinetics and pharmacodynamics of rucaparib as well as future and ongoing trials.

Rucaparib in ovarian cancer: an update on safety, efficacy and place in therapy

Rucaparib is a poly (ADP-ribose) polymerase (PARP) inhibitor and potent inhibitor of PARP1, PARP2 and PARP3 enzymes. Phase II and III trials have documented that rucaparib has single-agent antitumor activity in patients with high-grade ovarian carcinoma, with both BRCA-mutated (germline and somatic) and with homologous recombination deficiency (HRD). Rucaparib as a maintenance treatment showed increased progression-free survival in patients with ovarian carcinoma who achieved a response to platinum-based chemotherapy, with an acceptable safety profile. The approval of this drug, along with the companion diagnostic FoundationFocus CDxBRCA test represents an important new therapeutic option in the treatment of ovarian cancer. This article reviews the mechanisms of action, safety, pharmacokinetics and pharmacodynamics and indications for use of rucaparib as well as future trials.

Anticancer Gold(III) Peptidomimetics: From Synthesis to in vitro and ex vivo Biological Evaluations

Five new Au^III -peptidodithiocarbamato complexes of the type [Au^III Br₂ (dtc-AA₁ -AA₂ -OR] (in which AA₁ =N-methylglycine (Sar), l/d-Pro; AA₂ =l/d-Ala, α-aminoisobutyric acid (Aib); R=OtBu, triethylene glycol methyl ether), differing with regard to the amino acid sequence and/or the chiral amino acid configuration, were designed to enhance tumor selectivity and bioavailability. The gold(III)-based moiety was functionalized to exploit the targeting properties of the peptidomimetic ligand toward two peptide transporters (namely PEPT1 and PEPT2), which are upregulated in several tumor cells. The compounds were synthesized and fully characterized, mainly by means of elemental analysis, one- and two-dimensional NMR spectroscopy, FT-IR, and UV/Vis spectrophotometry. The crystal structures of three compounds were also solved by X-ray diffraction. In vitro cytotoxicity studies using a panel of human tumor cell lines (A549 [non-small-cell lung carcinoma], MCF-7 [breast cancer], A2780 [ovarian carcinoma], H1975 [non-small-cell lung carcinoma], H460 [large-cell lung carcinoma], and A431 [human epidermoid carcinoma]) showed the dtc-Pro-Aib-OtBu derivative to be very effective, with GI₅₀ values much lower than those of cisplatin. This complex was thus selected for evaluating stability under physiological conditions and possible interactions with serum albumin, as well in PARP-1 enzyme inhibition assays and preliminary ex vivo toxicity experiments on healthy rat tissues.