Inhibition of poly(ADP-ribose) polymerase down-regulates BRCA1 and RAD51 in a pathway mediated by E2F4 and p130

Tailored Treatment Strategies in First Line Therapy for Ovarian Cancer Patients: A Critical Review of the Literature

BACKGROUND

Ovarian cancer (OC) is a significant cause of cancer-related mortality in women globally, with a five-year survival rate of approximately 49%. Standard therapy involves cytoreductive surgery followed by chemotherapy. Its poor prognosis has driven interest in alternative therapies such as targeted molecular agents like bevacizumab and poly (ADP-ribose) polymerase inhibitors (PARPi).

MATERIALS AND METHODS

This review systematically searched PubMed from January 2018 to December 2023 for studies on PARPi in OC. Emphasis was on identifying relevant Phase III trials, extracting data on study design, patient demographics, and outcomes. Special focus was on assessing PARPi efficacy, safety, impact on quality of life, and ongoing trials, including those on Clinicaltrials.gov.

RESULTS

The efficacy of PARPi in first-line therapy for OC has been extensively studied. Trials like SOLO-1, PRIMA, and ATHENA-MONO have demonstrated significant improvements in progression-free survival (PFS) and overall survival (OS), particularly in patients with BRCA mutations. Additionally, the combination of PARPi with other agents like bevacizumab has shown promising results in extending PFS. However, PARPi treatment is associated with various adverse effects, including hematologic toxicities like anemia, thrombocytopenia, and neutropenia. While most adverse events are manageable, some patients may require dose adjustments or discontinuation of treatment. Importantly, PARPi maintenance therapy has not adversely affected health-related quality of life (HRQoL), with studies reporting similar HRQoL scores between PARPi-treated and placebo-treated patients.

CONCLUSIONS

PARPi offer effective treatment with manageable side effects, suitable even for medically fragile patients. Individualized dosing can optimize benefits while minimizing adverse events. Exploring diverse treatment approaches, particularly in patients with limited life expectancy or high disease burden, could improve outcomes. Ongoing research is investigating alternative therapies and combinations to broaden treatment options. Combining bevacizumab with PARPi may be justified for first-line and recurrent maintenance therapy. Regardless of mutational status, PARPi should be considered for maintenance therapy in newly diagnosed advanced OC. Platinum sensitivity remains crucial for treatment decisions and predicting survival outcomes.

Efficacy and safety of PARP inhibitors combined with antiangiogenic agents in the maintenance treatment of ovarian cancer: a systematic review and meta-analysis with trial sequential analysis of randomized controlled trials

Background: Poly (ADP-ribose) polymerase (PARP) inhibitor and antiangiogenic agent monotherapy have shown to be effective as maintenance treatment in patients with ovarian cancer (OC). However, there is currently a lack of evidence-based study to directly compare the effects of combination therapy with these two drugs. Therefore, this study aimed to compare the efficacy and safety of combination therapy with PARP inhibitors and antiangiogenic agents in women with OC using a meta-analysis. Methods: An exhaustive search of literature was undertaken using multiple databases, including PubMed, Web of Science, Embase, and the Cochrane Library to identify pertinent randomized controlled trials (RCTs) published up until 17 December 2023. The data on progression-free survival (PFS), overall survival (OS), and adverse events (AEs) were pooled. We computed the pooled hazard ratios (HRs) and their 95% confidence intervals (CIs) for PFS and OS, along with the relative risks (RRs) and 95% CIs for AEs. Trial sequential analysis, heterogeneity test, sensitivity analysis, and publication bias assessment were performed. Stata 12.0 and Software R 4.3.1 were utilized for all analyses. Results: This meta-analysis included 7 RCTs with a total of 3,388 participants. The overall analysis revealed that combination therapy of PARP inhibitors and antiangiogenic agents significantly improved PFS (HR = 0.615, 95% CI = 0.517-0.731; 95% PI = 0.379-0.999), but also increased the risk of AEs, including urinary tract infection (RR = 1.500, 95% CI = 1.114-2.021; 95% PI = 0.218-10.346), fatigue (RR = 1.264, 95% CI = 1.141-1.400; 95% PI = 1.012-1.552), headache (RR = 1.868, 95% CI = 1.036-3.369; 95% PI = 0.154-22.642), anorexia (RR = 1.718, 95% CI = 1.320-2.235; 95% PI = 0.050-65.480), and hypertension (RR = 5.009, 95% CI = 1.103-22.744; 95% PI = 0.016-1580.021) compared with PARP inhibitor or antiangiogenic agent monotherapy. Our study has not yet confirmed the benefit of combination therapy on OS in OC patients (HR = 0.885, 95% CI = 0.737-1.063). Additionally, subgroup analyses further showed that combination therapy resulted in an increased risk of AEs, encompassing thrombocytopenia, vomiting, abdominal pain, proteinuria, fatigue, headache, anorexia, and hypertension (all p < 0.05). Conclusion: Our study demonstrated the PFS benefit of combination therapy with PARP inhibitors and antiangiogenic agents in patients with OC. The OS result need to be updated after the original trial data is mature. Clinicians should be vigilant of AEs when administering the combination therapy in clinical practice. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023494482.

Bevacizumab, olaparib, and durvalumab in patients with relapsed ovarian cancer: a phase II clinical trial from the GINECO group

Most patients with advanced ovarian cancer (AOC) ultimately relapse after platinum-based chemotherapy. Combining bevacizumab, olaparib, and durvalumab likely drives synergistic activity. This open-label phase 2 study (NCT04015739) aimed to assess activity and safety of this triple combination in female patients with relapsed high-grade AOC following prior platinum-based therapy. Patients were treated with olaparib (300 mg orally, twice daily), the bevacizumab biosimilar FKB238 (15 mg/kg intravenously, once-every-3-weeks), and durvalumab (1.12 g intravenously, once-every-3-weeks) in nine French centers. The primary endpoint was the non-progression rate at 3 months for platinum-resistant relapse or 6 months for platinum-sensitive relapse per RECIST 1.1 and irRECIST. Secondary endpoints were CA-125 decline with CA-125 ELIMination rate constant K (KELIM-B) per CA-125 longitudinal kinetics over 100 days, progression free survival and overall survival, tumor response, and safety. Non-progression rates were 69.8% (90%CI 55.9%-80.0%) at 3 months for platinum-resistant relapse patients (N = 41), meeting the prespecified endpoint, and 43.8% (90%CI 29.0%-57.4%) at 6 months for platinum-sensitive relapse (N = 33), not meeting the prespecified endpoint. Median progression-free survival was 4.1 months (95%CI 3.5-5.9) and 4.9 months (95%CI 2.9-7.0) respectively. Favorable KELIM-B was associated with better survival. No toxic deaths or major safety signals were observed. Here we show that further investigation of this triple combination may be considered in AOC patients with platinum-resistant relapse.

NCI10066: a Phase 1/2 study of olaparib in combination with ramucirumab in previously treated metastatic gastric and gastroesophageal junction adenocarcinoma

BACKGROUND

Our preclinical work revealed tumour hypoxia induces homologous recombination deficiency (HRD), increasing sensitivity to Poly (ADP-ribose) polymerase inhibitors. We aimed to induce tumour hypoxia with ramucirumab thereby sensitising tumours to olaparib.

PATIENTS AND METHODS

This multi-institution single-arm Phase 1/2 trial enrolled patients with metastatic gastroesophageal adenocarcinoma refractory to ≥1 systemic treatment. In dose escalation, olaparib was evaluated at escalating dose levels with ramucirumab 8 mg/kg day 1 in 14-day cycles. The primary endpoint of Phase 1 was the recommended Phase 2 dose (RP2D), and in Phase 2 the primary endpoint was the overall response rate (ORR).

RESULTS

Fifty-one patients received ramucirumab and olaparib. The RP2D was olaparib 300 mg twice daily with ramucirumab 8 mg/kg. In evaluable patients at the RP2D the ORR was 6/43 (14%) (95% CI 4.7-25.6). The median progression-free survival (PFS) was 2.8 months (95% CI 2.3-4.2) and median overall survival (OS) was 7.3 months (95% CI 5.7-13.0). Non-statistically significant improvements in PFS and OS were observed for patients with tumours with mutations in HRD genes.

CONCLUSIONS

Olaparib and ramucirumab is well-tolerated with efficacy that exceeds historical controls with ramucirumab single agent for gastric cancer in a heavily pre-treated patient population.

Efficacy and Safety of PARP Inhibitor Therapy in Advanced Ovarian Cancer: A Systematic Review and Network Meta-analysis of Randomized Controlled Trials

AIMS

This study aims to evaluate the efficacy and safety of PARP inhibitor therapy in advanced ovarian cancer and identify the optimal treatment for the survival of patients.

BACKGROUND

The diversity of PARP inhibitors makes clinicians confused about the optimal strategy and the most effective BRCAm mutation-based regimen for the survival of patients with advanced ovarian cancer.

OBJECTIVES

The objective of this study is to compare the effects of various PARP inhibitors alone or in combination with other agents in advanced ovarian cancer.

METHODS

PubMed, Embase, Cochrane Library, and Web of Science were searched for relevant studies on PARP inhibitors for ovarian cancer. Bayesian network meta-analysis was performed using Stata 15.0 and R 4.0.4. The primary outcome was the overall PFS, and the secondary outcomes included OS, AE3, DISAE, and TFST.

RESULTS

Fifteen studies involving 5,788 participants were included. The Bayesian network metaanalysis results showed that olaparibANDAI was the most beneficial in prolonging overall PFS and non-BRCAm PFS, followed by niraparibANDAI. However, for BRCAm patients, olaparibTR might be the most effective, followed by niraparibANDAI. Olaparib was the most effective for the OS of BRCAm patients. AI, olaparibANDAI, and veliparibTR were more likely to induce grade 3 or higher adverse events. AI and olaparibANDAI were more likely to cause DISAE.

CONCLUSION

PARP inhibitors are beneficial to the survival of patients with advanced ovarian cancer. The olaparibTR is the most effective for BRCAm patients, whereas olaparibANDAI and niraparibANDAI are preferable for non-BRCAm patients. Other: More high-quality studies are desired to investigate the efficacy and safety of PARP inhibitors in patients with other genetic performances.

Anti-tumour and radiosensitising effects of PARP inhibitor on cervical cancer xenografts

This study evaluated the radiosensitising effect of niraparib; a poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor on HeLa cervical cancer cells in nude mice and explored its possible mechanism. Twenty-four 3-5-week-old female BALB/c nude mice, inoculated with HeLa cells into the right hind leg, were randomly assigned into eight groups with three mice per group and treated. The tumour volume was significantly reduced under niraparib + radiotherapy combination as compared to monotherapy and untreated mice. The tumour growth was significantly delayed by 23.33-39 days when treated with combination therapy (p<.05). Further, univariate analysis revealed prolonged time for tumour growth when radiotherapy was followed by niraparib (I.G.) rather than niraparib (I.P.) (p=.003). Combination therapy reduced levels of PARP-1 precursor, PARP-1 splicer, PAR and RAD51 protein with high expression of γ-H2AX/CC3 and low expression of Ki-67. Niraparib in combination with radiotherapy can enhance the formation of DNA double strand breaks in HeLa cells and up regulate the expression of γ-H2AX/CC3.IMPACT STATEMENTWhat is already known on this subject? Asia has the highest incidence of cervical cancer (58.2%). Poly(adenosine diphosphate-ribose) polymerases (PARPs) are family of enzymes involved in single-strand break (SSB) and double-strand break (DSB) repair pathways. Niraparib is an effective inhibitor of both PARP-1 and PARP-2 and has the ability to cross the blood-brain barrier.What the results of this study add? Our study demonstrated that the combination of niraparib and radiotherapy can significantly enhance the cytotoxicity induced by radiotherapy. The inhibition effect of radiotherapy combined with niraparib on the tumour growth of mice was prominent, thereby establishing the radio-sensitisation activity of niraparib.What are the implications of these findings for clinical practice and/or further research? Niraparib can improve the cytotoxic effect of radiotherapy by increasing the formation of DSBs and up regulating the expression of apoptotic protein in HeLa cells.

Exploring homologous recombination repair and base excision repair pathway genes for possible diagnostic markers in hematologic malignancies

Hematologic malignancies (HMs) are a collection of malignant transformations, originating from the cells in the bone marrow and lymphoid organs. HMs comprise three main types; leukemia, lymphoma, and multiple myeloma. Globally, HMS accounts for approximately 10% of newly diagnosed cancer. DNA repair pathways defend the cells from recurrent DNA damage. Defective DNA repair mechanisms such as homologous recombination repair (HRR), nucleotide excision repair (NER), and base excision repair (BER) pathways may lead to genomic instability, which initiates HM progression and carcinogenesis. Expression deregulation of HRR, NER, and BER has been investigated in various malignancies. However, no studies have been reported to assess the differential expression of selected DNA repair genes combinedly in HMs. The present study was designed to assess the differential expression of HRR and BER pathway genes including RAD51, XRCC2, XRCC3, APEX1, FEN1, PARP1, and XRCC1 in blood cancer patients to highlight their significance as diagnostic/ prognostic marker in hematological malignancies. The study cohort comprised of 210 blood cancer patients along with an equal number of controls. For expression analysis, q-RT PCR was performed. DNA damage was measured in blood cancer patients and controls using the comet assay and LORD Q-assay. Data analysis showed significant downregulation of selected genes in blood cancer patients compared to healthy controls. To check the diagnostic value of selected genes, the Area under curve (AUC) was calculated and 0.879 AUC was observed for RAD51 (p < 0.0001) and 0.830 (p < 0.0001) for APEX1. Kaplan-Meier analysis showed that downregulation of RAD51 (p < 0.0001), XRCC3 (p < 0.02), and APEX1 (p < 0.0001) was found to be associated with a significant decrease in survival of blood cancer patients. Cox regression analysis showed that deregulation of RAD51 (p < 0.0001), XRCC2 (p < 0.02), XRCC3 (p < 0.003), and APEX1 (p < 0.00001) was found to be associated with the poor prognosis of blood cancer patients. Comet assay showed an increased number of comets in blood cancer patients compared to controls. These results are confirmed by performing the LORD q-assay and an increased frequency of lesions/Kb was observed in selected genes in cancer patients compared to controls. Our results showed significant downregulation of RAD51, XRCC2, XRCC3, APEX1, FEN1, PARP1, and XRCC1 genes with increased DNA damage in blood cancer patients. The findings of the current research suggested that deregulated expression of HRR and BER pathway genes can act as a diagnostic/prognostic marker in hematologic malignancies.

Is It Time to Anticipate the Use of PARP Inhibition in Prostate Cancer Patients?

The increasing diffusion of genetic analysis regarding the pathogenetic variants (PVs) of genes involved in DNA Damage Repair (DDR) mechanisms and the development of Poly ADP ribose polymerase (PARP) inhibitors (PARPis) led to the first valid precision medicine option tailored toward metastatic prostate cancer (mPC). The concept of anticipation in the systemic treatment of mPC was initially adopted for androgen receptor signaling inhibitors (ARSIs) to describe the expansion of their indications, from the setting of the late-stage second-line treatment of metastatic castration-resistant prostate cancer (mCRPC) to first-line therapy in selected cases. There is already mounting evidence in favor of the anticipation of PARPis in the first line of mCRPC therapy, and further evidence in favor of mHSPC is emerging. Many studies have demonstrated the synergism between ARSIs and PARP inhibitors. Recent discoveries regarding the crosstalk between the androgen receptor (AR) and DNA repair mechanisms are disconnecting the use of PARPis from genetic analysis. The new message emerging is that the combination of PARPis with ARSIs may work independently of DDR mutational status. As a matter of fact, most of the recent trials analyzing the combination of PARPis with abiraterone or enzalutamide as a first-line therapy enrolled mCRPC patients irrespective of their mutational status. The PROPEL trial concluded that the advantage of the combination was independent of PV status, despite a higher advantage being reported in the BRCA1/2 mutated subgroup. The MAGNITUDE trial, however, showed a significant advantage only in the DDR mutated subgroup, and the DDR non-mutated cohort was closed for further enrollment. The combination of PARPis with ARSIs represents a significant strategy with a view to the anticipation and intensification of care in mPC. However, it should not nullify the advantages of precision medicine linked to the genetic analysis of DDR genes.

Efficacy and safety of fluzoparib combined with anlotinib in extensive stage small cell lung cancer after first-line platinum-based chemotherapy: a multi-center, single-arm prospective phase II clinical study (STAMP study)

BACKGROUND

Small-cell lung cancer (SCLC) is a highly aggressive and lethal malignancy that accounts for 10-15% of lung cancers, and it is generally divided into limited and extensive stage. The standard of care for patients with newly diagnosed extensive-stage SCLC (ES-SCLC) is still platinum-based chemotherapy and as maintenance therapy scheme. Although most parts of patients experience a significant tumor response to first-line therapy, the disease recurs invariably. Anlotinib hydrochloride, a novel oral multitarget tyrosine kinase inhibitor, has significant inhibitory activity against angiogenesis-related kinases, such as VEGFR, FGFR, PDGFR, and c-Kit kinase associated with tumor cell proliferation. Fluzoparib is a type of inhibitor of poly ADP ribose polymerase (PARP, including PARPl, PARP2 and PARP3). Previous studies have shown that Fluzoparib has a strong inhibitory effect on PARP1 activity at the molecular and cellular levels.

METHODS

This is a multi-center, prospective, single-arm phase II clinical study. A total of 50 ES-SCLC patients who experienced disease progression after first-line standard platinum-based chemotherapy with/without immune checkpoint inhibitors scheme, or within 6 months after the completion of treatment will be recruited. Those who had prior treatment with any PARP inhibitor or antiangiogenic agent includes anlotinib, bevacizumab, sorafenib, and thalidomide are excluded. Eligible patients will receive oral anlotinib 8 mg once daily and oral fluzoparib 150 mg twice daily until disease progression or intolerable toxicity. The primary endpoint is objective response rate (ORR).

DISCUSSION

The addition of fluzoparib to anlotinib is expected to increase the clinical benefit in ES-SCLC patients after platinum-based chemotherapy.

TRIAL REGISTRATION

This study protocol was prospectively registered on June 17, 2021.

CLINICALTRIALS

gov Identifier: NCT04933175 .

Hesperetin effect on MLH1 and MSH2 expression on breast cancer cells BT-549

Due to its genetic and phenotypic heterogeneity, breast cancer is very difficult to eliminate. The harmful consequences of conventional therapies like radiation and chemotherapy have prompted the search for organic-based alternatives. Hesperetin (HSP), a flavonoid, has been discovered to possess the ability to hinder the proliferation of cell associated with breast cancer by acting as an epigenetic agent and modifying gene expression. In this investigation, breast cancer cells (BT-549) and normal cells (MCF-10a) were subjected to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test and three different doses (200, 400, and 600 μM/mL) of HSP for real-time polymerase chain reaction and flow cytometry to examine its cytotoxic and anti-malignant potential. HSP was shown to be cytotoxic to both normal and breast cancer cells, but had a more pronounced effect on the cancer cell lines. After 48 h of treatment, the half-maximal inhibitory concentration (IC50) for BT-549 was 279.2 μM/mL, whereas the IC50 for MCF-10a was 855.4 μM/mL. At high HSP concentrations, upregulation of the MLH1 and MSH2 genes was observed in both cell lines. The influence of HSP on MLH1 gene expression was concentration dependent. Moreover, HSP had a concentration-dependent effect on MSH2 gene expression in the BT-549 cell line but not in the MCF-10a cell line. Cell death and early apoptosis were shown to be concentration dependent upon the application of HSP, as determined by flow cytometric analysis. HSP's capacity to cause apoptosis and its stronger impact on the malignant cell line when analyzed with the normal cell line imply that it might be useful as an effective therapeutic approach for combating breast cancer.

Therapeutic Targeting of DNA Replication Stress in Cancer

This article reviews the currently used therapeutic strategies to target DNA replication stress for cancer treatment in the clinic, highlighting their effectiveness and limitations due to toxicity and drug resistance. Cancer cells experience enhanced spontaneous DNA damage due to compromised DNA replication machinery, elevated levels of reactive oxygen species, loss of tumor suppressor genes, and/or constitutive activation of oncogenes. Consequently, these cells are addicted to DNA damage response signaling pathways and repair machinery to maintain genome stability and support survival and proliferation. Chemotherapeutic drugs exploit this genetic instability by inducing additional DNA damage to overwhelm the repair system in cancer cells. However, the clinical use of DNA-damaging agents is limited by their toxicity and drug resistance often arises. To address these issues, the article discusses a potential strategy to target the cancer-associated isoform of proliferating cell nuclear antigen (caPCNA), which plays a central role in the DNA replication and damage response network. Small molecule and peptide agents that specifically target caPCNA can selectively target cancer cells without significant toxicity to normal cells or experimental animals.

Quantitative DNA Repair Biomarkers and Immune Profiling for Temozolomide and Olaparib in Metastatic Colorectal Cancer

Purpose

O6-methylguanine DNA methyltransferase (MGMT)-silenced tumors reveal sensitivity to temozolomide (TMZ), which may be enhanced by PARP inhibitors. Approximately 40% of colorectal cancer has MGMT silencing and we aimed to measure antitumoral and immunomodulatory effects from TMZ and olaparib in colorectal cancer.

Experimental Design

Patients with advanced colorectal cancer were screened for MGMT promoter hypermethylation using methylation-specific PCR of archival tumor. Eligible patients received TMZ 75 mg/m2 days 1-7 with olaparib 150 mg twice daily every 21 days. Pretreatment tumor biopsies were collected for whole-exome sequencing (WES), and multiplex quantitative immunofluorescence (QIF) of MGMT protein expression and immune markers.

Results

MGMT promoter hypermethylation was detected in 18/51 (35%) patients, 9 received study treatment with no objective responses, 5/9 had stable disease (SD) and 4/9 had progressive disease as best response. Three patients had clinical benefit: carcinoembryonic antigen reduction, radiographic tumor regression, and prolonged SD. MGMT expression by multiplex QIF revealed prominent tumor MGMT protein from 6/9 patients without benefit, while MGMT protein was lower in 3/9 with benefit. Moreover, benefitting patients had higher baseline CD8+ tumor-infiltrating lymphocytes. WES revealed 8/9 patients with MAP kinase variants (7 KRAS and 1 ERBB2). Flow cytometry identified peripheral expansion of effector T cells.

Conclusions

Our results indicate discordance between MGMT promoter hypermethylation and MGMT protein expression. Antitumor activity seen in patients with low MGMT protein expression, supports MGMT protein as a predictor of alkylator sensitivity. Increased CD8+ TILs and peripheral activated T cells, suggest a role for immunostimulatory combinations.

Significance

TMZ and PARP inhibitors synergize in vitro and in vivo in tumors with MGMT silencing. Up to 40% of colorectal cancer is MGMT promoter hypermethylated, and we investigated whether TMZ and olaparib are effective in this population. We also measured MGMT by QIF and observed efficacy only in patients with low MGMT, suggesting quantitative MGMT biomarkers more accurately predict benefit to alkylator combinations.

Pancreatic Cancer: BRCA Targeted Therapy and Beyond

Pancreatic ductal adenocarcinoma (PDAC) is projected to become the second leading cause of cancer-related death in the US by 2030, despite accounting for only 5% of all cancer diagnoses. Germline gBRCA1/2-mutated PDAC represents a key subgroup with a favorable prognosis, due at least in part to additional approved and guideline-endorsed therapeutic options compared with an unselected PDAC cohort. The relatively recent incorporation of PARP inhibition into the treatment paradigm for such patients has resulted in renewed optimism for a biomarker-based approach to the management of this disease. However, gBRCA1/2 represents a small subgroup of patients with PDAC, and efforts to extend the indication for PARPi beyond BRCA1/2 mutations to patients with PDAC and other genomic alterations associated with deficient DNA damage repair (DDR) are ongoing, with several clinical trials underway. In addition, despite an array of approved therapeutic options for patients with BRCA1/2-associated PDAC, both primary and acquired resistance to platinum-based chemotherapies and PARPi presents a significant challenge in improving long-term outcomes. Herein, we review the current treatment landscape of PDAC for patients with BRCA1/2 and other DDR gene mutations, experimental approaches under investigation or in development, and future directions.

Metastatic Colorectal Cancer Patient with Microsatellite Stability and Germline BRAC2 Mutation Shows a Complete Response to Olaparib in Combination with a PD-1 Inhibitor and Bevacizumab: A Case Report and Review of the Literature

Metastatic colorectal cancer (mCRC) has a poor prognosis. Combining chemotherapy with targeted therapy constitutes a basic form of mCRC treatment. Immune checkpoint inhibitors have been recommended for microsatellite instability mCRC, while most patients harboring microsatellite stability (MSS) or proficient mismatch repair (pMMR) are less responsive to immunotherapy. Combinational targeted therapy, including poly-ADP ribose polymerase (PARP) inhibitors, has been considered a promising way to reverse immunotherapy resistance; however, there is no clear and consistent conclusions can be drawn from the current research. Here, we report the case of a 59-year-old woman diagnosed with stage IVB MSS mCRC who received three courses of capecitabine/oxaliplatin chemotherapy combined with bevacizumab as a first-line treatment, resulting in an overall evaluation of stable disease (-25.7%). However, the occurrence of adverse events of intolerable grade 3 diarrhea and vomiting forced the cessation of this therapy. A germline BRCA2 mutation was found by next-generation sequencing, and the patient further received a combination of olaparib, tislelizumab, and bevacizumab. This treatment regime resulted in a complete metabolic response and a partial response (-50.9%) after 3 months of treatment. Mild asymptomatic interstitial pneumonia and manageable hematologic toxicity were two adverse events associated with this combination therapy. This study provides new insights into the combination of PARP inhibitors and immunotherapy for MSS mCRC patients carrying germline BRCA2 mutations.

Randomized Trial of Olaparib With or Without Cediranib for Metastatic Castration-Resistant Prostate Cancer: The Results From National Cancer Institute 9984

PURPOSE

Cediranib, a pan-vascular endothelial growth factor receptor inhibitor, suppresses expression of homologous recombination repair (HRR) genes and increases sensitivity to poly-(ADP-ribose) polymerase inhibition in preclinical models. We investigated whether cediranib combined with olaparib improves the clinical outcomes of patients with prostate cancer.

METHODS

Patients with progressive metastatic castration-resistant prostate cancer (mCRPC) were randomly assigned 1:1 to arm A: cediranib 30 mg once daily plus olaparib 200 mg twice daily or arm B: olaparib 300 mg twice daily alone. The primary end point was radiographic progression-free survival (rPFS) in the intention-to-treat patients. The secondary end points were rPFS in patients with HRR-deficient and HRR-proficient mCRPC.

RESULTS

In the intention-to-treat set of 90 patients, median rPFS was 8.5 (95% CI, 5.4 to 12.0) and 4.0 (95% CI, 3.2 to 8.5) months in arms A and B, respectively. Cediranib/olaparib significantly improved rPFS versus olaparib alone (hazard ratio [HR], 0.617; 95% CI, 0.392 to 0.969; P = .0359). Descriptive analyses showed a median rPFS of 10.6 (95% CI, 5.9 to not assessed [NA]) and 3.8 (95% CI, 2.33 to NA) months (HR, 0.64; 95% CI, 0.272 to 1.504) among patients with HRR-deficient mCRPC, and 13.8 (95% CI, 3.3 to NA) and 11.3 (95% CI, 3.8 to NA) months (HR, 0.98; 95% CI, 0.321 to 2.988) among patients with BRCA2-mutated mCRPC in arms A and B, respectively. The incidence of grades 3-4 adverse events was 61% and 18% in arms A and B, respectively.

CONCLUSION

Cediranib combined with olaparib improved rPFS compared with olaparib alone in men with mCRPC. This combination was associated with an increased incidence of grades 3-4 adverse events. BRCA2-mutated subgroups treated with olaparib with or without cediranib were associated with a numerically longer median rPFS.

The PARP inhibitor Rucaparib synergizes with radiation to attenuate atypical teratoid rhabdoid tumor growth

Background

Atypical teratoid rhabdoid tumors (ATRT) are highly aggressive pediatric brain tumors. The available treatments rely on toxic chemotherapy and radiotherapy, which themselves can cause poor outcomes in young patients. Poly (ADP-ribose) polymerases (PARP), multifunctional enzymes which play an important role in DNA damage repair and genome stability have emerged as a new target in cancer therapy. An FDA-approved drug screen revealed that Rucaparib, a PARP inhibitor, is important for ATRT cell growth. This study aims to investigate the effect of Rucaparib treatment in ATRT.

Methods

This study utilized cell viability, colony formation, flow cytometry, western blot, immunofluorescence, and immunohistochemistry assays to investigate Rucaparib's effectiveness in BT16 and MAF737 ATRT cell lines. In vivo, intracranial orthotopic xenograft model of ATRT was used. BT16 cell line was transduced with a luciferase-expressing vector and injected into the cerebellum of athymic nude mice. Animals were treated with Rucaparib by oral gavaging and irradiated with 2 Gy of radiation for 3 consecutive days. Tumor growth was monitored using In Vivo Imaging System.

Results

Rucaparib treatment decreased ATRT cell growth, inhibited clonogenic potential of ATRT cells, induced cell cycle arrest and apoptosis, and led to DNA damage accumulation as shown by increased expression of γH2AX. In vivo, Rucaparib treatment decreased tumor growth, sensitized ATRT cells to radiation and significantly increased mice survival.

Conclusion

We demonstrated that Rucaparib has potential to be a new therapeutic strategy for ATRT as seen by its ability to decrease ATRT tumor growth both in vitro and in vivo.

Mechanisms of Drug Resistance in Ovarian Cancer and Associated Gene Targets

In the United States, over 100,000 women are diagnosed with a gynecologic malignancy every year, with ovarian cancer being the most lethal. One of the hallmark characteristics of ovarian cancer is the development of resistance to chemotherapeutics. While the exact mechanisms of chemoresistance are poorly understood, it is known that changes at the cellular and molecular level make chemoresistance challenging to treat. Improved therapeutic options are needed to target these changes at the molecular level. Using a precision medicine approach, such as gene therapy, genes can be specifically exploited to resensitize tumors to therapeutics. This review highlights traditional and novel gene targets that can be used to develop new and improved targeted therapies, from drug efflux proteins to ovarian cancer stem cells. The review also addresses the clinical relevance and landscape of the discussed gene targets.

PARP-1 genetic polymorphism associated with radiation sensitivity of non-small cell lung cancer

About 70% of non-small cell lung cancer (NSCLC) patients require radiotherapy. However, due to the difference in radiation sensitivity, the treatment outcome may differ for the same pathology and choice of treatment. Poly (ADP-ribose) polymerase 1 (PARP-1) is a key gene responsible for DNA repair and is involved in base excision repair as well as repair of single strand break induced by ionizing radiation and oxidative damage. In order to investigate the relationship between PARP-1 gene polymorphism and radiation sensitivity in NSCLC, we collected 141 primary NSCLC patients undergoing three-dimensional conformal radiotherapy. For each case, the gross tumor volumes (GTV) before radiation and that after 40 Gy radiation were measured to calculate the tumor regression rate. TaqMan real-time polymerase chain reaction was performed to genotype the single-nucleotide polymorphisms (SNPs). Genotype frequencies for PARP-1 genotypes were 14.2% for C/C, 44.7% for C/G and 41.1% for G/G. The average tumor regression rate after 40 Gy radiation therapy was 35.1% ± 0.192. Tumor regression rate of mid-term RT of C/C genotype was 44.6% ± 0.170, which was higher than that of genotype C/G and G/G (32.4% ± 0.196 and 34.8% ± 0.188, respectively) with statistical significance (F = 3.169 p = 0.045). The higher tumor regression rate in patients with C/C genotype suggested that G allele was a protective factor against radiation therapy. Using the median tumor regression rate of 34%, we divided the entire cohort into two groups, and found that the frequency distribution of PARP-1 gene rs3219073 had significant difference between these two groups (p < 0.05). These results showed that PARP-1 gene polymorphism may affect patient radiation sensitivity and predict the efficacy of radiotherapy. It therefore presents an opportunity for developing new therapeutic targets to improve radiotherapy outcome.

Overview of fuzuloparib in the treatment of ovarian cancer: background and future perspective

Over the last decade, clinical trials using various poly ADP ribose polymerase (PARP) inhibitors on patients with ovarian cancer have shown promising results. The introduction of PARP inhibitors has changed the treatment landscape and improved outcomes for patients with ovarian cancer. Fuzuloparib, developed by Jiangsu Hengrui Pharmaceuticals Co., Ltd., is a novel orally available small molecule PARP inhibitor. By introducing the trifluoromethyl group into chemical structure, fuzuloparib exhibits higher stability and lower inter-individual variability than other PARP inhibitors. Several clinical trials (FZOCUS series and others) have been carried out to assess the efficacy and safety of fuzuloparib through different lines of treatments for advanced or recurrent ovarian cancer in both treatment and maintenance. Here, we present the most recent data from these studies, discuss current progress and potential future directions.

E2F4 transcription factor is a prognostic biomarker related to immune infiltration of head and neck squamous cell carcinoma

To investigate the relationship between the transcription factor, E2F4, and head and neck squamous cell carcinoma (HNSCC), and to preliminarily explore the signaling pathways and immunological role of E2F4. The mRNA expression of E2F4 in HNSCC was evaluated by searching Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) datasets. E2F4 protein expression was analyzed by immunohistochemistry using the CMU1h-ENT database. The association between E2F4 expression and tumor infiltration of immune cells was analyzed. Intracellular signaling by E2F4 was explored using KEGG and GO analysis. The correlation of E2F4 expression with clinical characteristics and its prognostic role were validated and analyzed in TCGA database. From the analysis of GEO and TCGA data, E2F4 expression was found to be up-regulated in HNSCC tumor tissues, and its level was associated with T, Grade, and M staging. Kaplan–Meier curve and Cox analyses indicated that the high expression of E2F4 was related to a poor prognosis. Thus, E2F4 was considered a potential prognostic factor for HNSCC. Immunohistochemical staining showed that E2F4 was mainly localized in the cell nucleus; it was highly expressed in HNSCC tissues, with a significant difference noted from that in pericancerous mucosa tissues. A correlation was observed between the differential expression of E2F4 and the immune infiltration of HNSCC. As revealed by KEGG and GO analysis, differential enrichment was found in the cell cycle, spliceosome, meiosis, microbial polysaccharide synthesis, and WNT signaling pathway, as well as in cyclic adenosine monophosphate, ERBB2, VEGF, GCNP and MYC pathways. E2F4 plays an important role in tumor progression and may be a critical biological prognostic factor for HNSCC. In addition, it functions in the nucleus as a transcription factor, regulates immune cells, and could be a promising molecular target for the diagnosis and treatment of HNSCC.

Clinical Landscape of PARP Inhibitors in Ovarian Cancer: Molecular Mechanisms and Clues to Overcome Resistance

Simple Summary

Recent development of maintenance therapy using PARP inhibitors in ovarian cancer has led to a significant improvement in survival rates. However, resistance to these inhibitors can occur in patients, causing disease progression or relapse. Consequently, novel treatment strategies are urgently needed to overcome this resistance. This review article focuses on the precise molecular mechanisms by which PARP inhibitors exert their antitumor effects, as well as how they elicit resistance, in order to gain insight into novel therapeutic approaches to overcome PARP inhibitor resistance in ovarian cancer.

Abstract

The survival of patients with advanced or recurrent ovarian cancer has improved tremendously in the past decade, mainly due to the establishment of maintenance therapy with poly (ADP-ribose) polymerase (PARP) inhibitors (PARPis) after conservative chemotherapies. Despite their superior efficacy, resistance to PARPis has been reported, and patients with resistance have a much worse prognosis. Therefore, the development of novel treatment strategies to overcome PARPi resistance is urgently needed. The present review article focuses on the molecular mechanisms of how PARPis exert cytotoxic effects on cancer cells through DNA repair processes, especially the genetic background and tumor microenvironment favored by PARPis. Furthermore, currently available information on PARPi resistance mechanisms is introduced and discussed to develop a novel therapeutic approach against them.

PARP inhibitors in hereditary breast and ovarian cancer and other cancers: A review

There has been a paradigm shift in the management of cancer, with the immense progress in cancer genomics. More and more targeted therapies are becoming available by the day and personalized medicine is becoming popular with specific drugs being designed for selected subgroups of patients. One such new class of targeted drugs in the armamentarium is Poly ADP Ribose Polymerase (PARP) inhibitors (PARPi), which inhibit the enzyme PARP, thus interfering with DNA repair. This strategy utilizes a pre-existing genomic lesion in tumors with homologous recombination repair defects (including BRCA mutations), weakening tumor cells further by blocking the alternate pathway of DNA repair. In this review, we discuss in detail, the evolution, genetics, mechanism of action, mechanism of resistance, indications of use of PARP inhibitors, as well as combination with other agents and future directions.

Vulnerability of IDH1-Mutant Cancers to Histone Deacetylase Inhibition via Orthogonal Suppression of DNA Repair

Exploitation of DNA repair defects has enabled major advances in treating specific cancers. Recent work discovered that the oncometabolite 2-hydroxyglutarate (2-HG), produced by neomorphic isocitrate dehydrogenase 1/2 (IDH1/2) mutations, confers a homology-directed repair (HDR) defect through 2-HG-induced histone hypermethylation masking HDR signaling. Here, we report that IDH1-mutant cancer cells are profoundly sensitive to the histone deacetylase inhibitor (HDACi) vorinostat, by further suppressing the residual HDR in 2-HG-producing cells. Vorinostat downregulates repair factors BRCA1 and RAD51 via disrupted E2F-factor regulation, causing increased DNA double-strand breaks, reduced DNA repair factor foci, and functional HDR deficiency even beyond 2-HG's effects. This results in greater cell death of IDH1-mutant cells and confers synergy with radiation and PARPi, both against cells in culture and patient-derived tumor xenografts. Our work identifies HDACi's utility against IDH1-mutant cancers, and presents IDH1/2 mutations as potential biomarkers to guide trials testing HDACi in gliomas and other malignancies. IMPLICATIONS: IDH1-mutant cells show profound vulnerability to HDACi treatment, alone and with PARPi and radiation, via HDR suppression, presenting IDH1/2 mutations as biomarkers for HDACi use in gliomas and other malignancies.

Therapeutic targeting of the hypoxic tumour microenvironment

Hypoxia is prevalent in human tumours and contributes to microenvironments that shape cancer evolution and adversely affect therapeutic outcomes. Historically, two different tumour microenvironment (TME) research communities have been discernible. One has focused on physicochemical gradients of oxygen, pH and nutrients in the tumour interstitium, motivated in part by the barrier that hypoxia poses to effective radiotherapy. The other has focused on cellular interactions involving tumour and non-tumour cells within the TME. Over the past decade, strong links have been established between these two themes, providing new insights into fundamental aspects of tumour biology and presenting new strategies for addressing the effects of hypoxia and other microenvironmental features that arise from the inefficient microvascular system in solid tumours. This Review provides a perspective on advances at the interface between these two aspects of the TME, with a focus on translational therapeutic opportunities relating to the elimination and/or exploitation of tumour hypoxia.

[Place of PARP inhibitors in the treatment of endometrial and cervical cancers]

New molecular therapeutic approaches have emerged in recent years for advanced gynaecological cancers, including targeted therapies such as poly-ADP-ribose polymerase inhibitors (PARPi). These have demonstrated efficacy in high-grade serous ovarian cancers in patients carrying a mutation in the BRCA gene, which predisposes them to breast and ovarian cancers. Clinical and pre-clinical data suggest that the activity of PARPi inhibitors may not be limited to BRCA mutated tumours and may involve the homologous recombination pathway. These data raise the question of the potential efficacy of PARPi in advanced endometrial and cervical cancers where treatment options are currently limited. At present, there are few data available on the activity of PARPi in endometrial and cervical cancers, but some results seem promising. In this review, we present a synthesis of the available studies concerning PARPi in endometrial and cervical cancer.

SPINDOC binds PARP1 to facilitate PARylation

SPINDOC is tightly associated with the histone H3K4me3 effector protein SPIN1. To gain a better understanding of the biological roles of SPINDOC, we identified its interacting proteins. Unexpectedly, SPINDOC forms two mutually exclusive protein complexes, one with SPIN1 and the other with PARP1. Consistent with its ability to directly interact with PARP1, SPINDOC expression is induced by DNA damage, likely by KLF4, and recruited to DNA lesions with dynamics that follows PARP1. In SPINDOC knockout cells, the levels of PARylation are reduced, in both the absence and presence of DNA damage. The SPINDOC/PARP1 interaction promotes the clearance of PARP1 from damaged DNA, and also impacts the expression of known transcriptional targets of PARP1. To address the in vivo roles of SPINDOC in PARP1 regulation, we generate SPINDOC knockout mice, which are viable, but slightly smaller than their wildtype counterparts. The KO mice display reduced levels of PARylation and, like PARP1 KO mice, are hypersensitive to IR-induced DNA damage. The findings identify a SPIN1-independent role for SPINDOC in the regulation of PARP1-mediated PARylation and the DNA damage response.

SPINDOC is known to interact with Spindlin1 (SPIN1), a histone code effector protein. Here, the authors show that SPINDOC is distributed between two distinct protein complexes, one comprising SPIN1 and the other one with PARP1. Their results suggest a role for SPINDOC in the regulation of PARP1- mediated PARylation and the DNA damage response.

BRCA1 Expression and Outcome in Patients With EGFR-Mutant NSCLC Treated With Gefitinib Alone or in Combination With Olaparib

Introduction

DNA repair capacity, as exemplified by BRCA1 gene expression, is related with outcome to EGFR tyrosine kinase inhibitors in patients with EGFR-mutant NSCLC. Olaparib, a PARP inhibitor, reduces BRCA1 expression. Olaparib was tested in combination with gefitinib versus gefitinib single agent, as a first-line therapy for patients with EGFR-mutant NSCLC in the GOAL study (trial registration: NCT01513174). Here, we report the results of the biomarker-related prespecified secondary objectives of the GOAL study.

Methods

We evaluated the impact of BRCA1 mRNA expression in 91 patients with EGFR-mutant NSCLC. Of those 91 patients, 51 were randomized to treatment with gefitinib and 40 were randomized to treatment with gefitinib plus olaparib. We explored in vitro whether BRCA1 mRNA levels are related with outcome to gefitinib plus olaparib. The expression levels of 53BP1, CtIP, and AXL were also explored and correlated with the treatment outcome.

Results

Overall, as what happened in the GOAL study, no statistically significant difference was observed in median progression-free survival (PFS) between the two treatment arms, for the 91 patients of the present study (p = 0.2419). For patients with high BRCA1 mRNA expression (BRCA1-high group), median PFS was 12.9 months in the gefitinib plus olaparib arm, compared with 9.2 months in the gefitinib arm (p = 0.0449). In the gefitinib arm, median PFS was 9.1 months for the BRCA1-high group and 10.2 months for the BRCA1-low group (p = 0.0193). We observed a more pronounced synergism of gefitinib plus olaparib in cells with higher BRCA1 compared with those with low BRCA1 mRNA expression.

Conclusions

High BRCA1 mRNA expression identified patients with NSCLC who benefited from gefitinib plus olaparib in the GOAL phase 2 clinical trial.

Biology of the Radio- and Chemo-Responsiveness in HPV Malignancies

In multiple anatomic sites, patients with cancers associated with the Human Papillomavirus (HPV) experience better locoregional control and overall survival after radiotherapy and/or chemoradiotherapy than patients with HPV-negative cancers. These improved outcomes suggest that relatively unique biological features in HPV-positive cancers may increase sensitivity to DNA damaging agents as well as an impaired DNA damage response. This review will address potential biological mechanisms driving this increased sensitivity of HPV-positive cancer to radiation and/or chemotherapy. This review will discuss the clinical and preclinical observations that support the intrinsic radiosensitivity and/or chemosensitivity of HPV-positive cancers. Furthermore, this review will highlight the molecular mechanisms for increased radiation sensitivity using the classical "4 Rs" of radiobiology: repair, reassortment, repopulation, and reoxygenation. First, HPV-positive cancers have increased DNA damage due to increased oxidative stress and impaired DNA damage repair due to the altered activity TP53, p16, TIP60, and other repair proteins. Second, irradiated HPV-positive cancer cells display increased G2/M arrest leading to reassortment of cancer cells in more radiosensitive phases of the cell cycle. In addition, HPV-positive cancers have less radioresistant cancer stem cell subpopulations that may limit their repopulation during radiotherapy. Finally, HPV-positive cancers may also have less hypoxic tumor microenvironments that make these cancers more sensitive to radiation than HPV-negative cells. We will also discuss extrinsic immune and microenvironmental factors enriched in HPV-positive cancers that facilities responses to radiation. Therefore, these potential biological mechanisms may underpin the improved clinical outcomes often observed in these virally induced cancers.

Targeting DNA damage repair pathways in pancreas cancer

Pancreas ductal adenocarcinoma (PDAC) is the third most common cause of cancer death in the USA. While other cancers with historically poor prognoses have benefited from new immunotherapies and targeted agents, the 5-year survival rate for PDAC patients has remained static. The accessibility to genomic testing has improved in recent years, and it is now clear that PDAC is a heterogenous disease, with a subset of patients harboring actionable mutations. There are several targeted therapies approved by the Food and Drug administration (FDA) in PDAC: EGFR inhibitor erlotinib (combined with gemcitabine) in unselected patients, TRK inhibitors larotrectinib and entrectinib for patients with NTRK fusion mutation, the PD-1 inhibitor pembrolizumab for mismatch repair-deficient patients, and the poly-ADP-ribose polymerase (PARP) inhibitor olaparib in patients with germline BRCA mutation as a maintenance therapy. DNA damage repair (DDR) is paramount to genomic integrity and cell survival. The defective repair of DNA damage is one of the hallmarks of cancer, and abnormalities in DDR pathways are closely linked with the development of malignancies and upregulation of these pathways linked with resistance to treatment. The prevalence of somatic and germline mutations in DDR pathways in metastatic PDAC is reported to be approximately 15-25%. Patients with DDR gene alterations benefit from a personalized approach to treatment. Recently, the POLO trial demonstrated a progression-free survival (PFS) benefit in metastatic PDAC patients with a germline BRCA1/2 mutation treated with maintenance olaparib following platinum-based induction chemotherapy. This was the first phase 3 randomized trial to establish a biomarker-driven approach in the treatment of PDAC and establishes a precedent for maintenance therapy in PDAC. The review herein aims to outline the current treatment landscape for PDAC patients with DDR gene-mutated tumors, highlight novel therapeutic approaches focused on surmounting tumor resistance, and explore new strategies which may lead to an expansion in the number of patients who benefit from these targeted treatments.

Therapeutic Potential of PARP Inhibitors in the Treatment of Gastrointestinal Cancers

Gastrointestinal (GI) malignancies are a major global health burden, with high mortality rates. The identification of novel therapeutic strategies is crucial to improve treatment and survival of patients. The poly (ADP-ribose) polymerase (PARP) enzymes involved in the DNA damage response (DDR) play major roles in the development, progression and treatment response of cancer, with PARP inhibitors (PARPi) currently used in the clinic for breast, ovarian, fallopian, primary peritoneal, pancreatic and prostate cancers with deficiencies in homologous recombination (HR) DNA repair. This article examines the current evidence for the role of the DDR PARP enzymes (PARP1, 2, 3 and 4) in the development, progression and treatment response of GI cancers. Furthermore, we discuss the role of HR status as a predictive biomarker of PARPi efficacy in GI cancer patients and examine the pre-clinical and clinical evidence for PARPi and cytotoxic therapy combination strategies in GI cancer. We also include an analysis of the genomic and transcriptomic landscape of the DDR PARP genes and key HR genes (BRCA1, BRCA2, ATM, RAD51, MRE11, PALB2) in GI patient tumours (n = 1744) using publicly available datasets to identify patients that may benefit from PARPi therapeutic approaches.

Direct Arylation in the Presence of Palladium Pincer Complexes

Direct arylation is an atom-economical alternative to more established procedures such as Stille, Suzuki or Negishi arylation reactions. In comparison with other palladium sources and ligands, the use of palladium pincer complexes as catalysts or pre-catalysts for direct arylation has resulted in improved efficiency, higher reaction yields, and advantageous reaction conditions. In addition to a revision of the literature concerning intra- and intermolecular direct arylation reactions performed in the presence of palladium pincer complexes, the role of these remarkably active catalysts will also be discussed.

Perspectives on PARP inhibitors as pharmacotherapeutic strategies for breast cancer

Introduction Approximately 10% of all breast cancer cases occur in individuals who have germline pathogenic variants of the BRCA 1, BRCA 2, and other genes associated with impaired DNA damage repair that is associated with an increased risk of breast, ovarian, and other cancers. Inhibitors of poly-ADP ribose polymerase (PARP) induce synthetic lethality in cancer cells harboring such pathogenic variants.Area covered In this review, the authors review the mechanisms of action, antitumor activity, and adverse events associated with PARP inhibitors for the treatment of advanced breast cancer. The authors then summarize the area and provide their expert perspectives on the area.Expert opinion Two PARP inhibitors are approved in metastatic breast cancer, including olaparib and talozaparib. Both agents were approved based on phase III trials demonstrating that they were associated with improved progression-free survival compared with treatment of physician's choice in patients receiving second-third line therapy for locally advanced, inoperable, or metastatic breast cancer in patients with germline pathogenic BRCA 1 or BRCA2 variants.

Eliminating hypoxic tumor cells improves response to PARP inhibitors in homologous recombination-deficient cancer models

Hypoxia, a hallmark feature of the tumor microenvironment, causes resistance to conventional chemotherapy, but was recently reported to synergize with poly(ADP-ribose) polymerase inhibitors (PARPis) in homologous recombination-proficient (HR-proficient) cells through suppression of HR. While this synergistic killing occurs under severe hypoxia (<0.5% oxygen), our study shows that moderate hypoxia (2% oxygen) instead promotes PARPi resistance in both HR-proficient and -deficient cancer cells. Mechanistically, we identify reduced ROS-induced DNA damage as the cause for the observed resistance. To determine the contribution of hypoxia to PARPi resistance in tumors, we used the hypoxic cytotoxin tirapazamine to selectively kill hypoxic tumor cells. We found that the selective elimination of hypoxic tumor cells led to a substantial antitumor response when used with PARPi compared with that in tumors treated with PARPi alone, without enhancing normal tissue toxicity. Since human breast cancers with BRAC1/2 mutations have an increased hypoxia signature and hypoxia reduces the efficacy of PARPi, then eliminating hypoxic tumor cells should enhance the efficacy of PARPi therapy.

Complete pathological response to olaparib and bevacizumab in advanced cervical cancer following chemoradiation in a BRCA1 mutation carrier: a case report

BACKGROUND

Homologous recombination deficiency is a marker of response to poly(ADP-ribose) polymerase inhibitors in different cancer types including ovary, prostate, and pancreatic cancer. To date, no report about poly(ADP-ribose) polymerase inhibitors has been published on cervical cancer.

CASE PRESENTATION

Here we present the case of a patient with cervical cancer treated in this setting. A 49-year-old woman diagnosed with International Federation of Obstetricians and Gynecologists stage 2018 IIIC2 locally advanced undifferentiated cervical cancer received first-line chemoradiotherapy followed by carboplatin, paclitaxel, and bevacizumab with partial response. Because of a family history of cancers, the patient was tested and found positive for a pathogenic BRCA1 germline and somatic mutation, which motivated bevacizumab plus olaparib maintenance treatment. A simple hysterectomy was performed after 2 years stable disease; pathological report showed complete pathological response, and 12 months follow-up showed no recurrence.

CONCLUSION

Poly(ADP-ribose) polymerase inhibitors could be an alternative maintenance treatment for patients with persistent advanced cervical cancer previously treated with platinum, especially when familial history of cancers is reported. Clinical trials using poly(ADP-ribose) polymerase inhibitors for advanced cervical cancer are warranted.

Emerging Therapeutics for Patients with Triple-Negative Breast Cancer

PURPOSE OF REVIEW

Triple negative breast cancer (TNBC) accounts for approximately 10-15% of all breast cancers and it is associated with a poor prognosis. However, recent new effective treatment strategies have improved its outcomes. The aim of this review is to provide an overview on the emerging therapeutics for TNBC, describing both previously approved therapies that are currently being repurposed, as well as new target therapies that may improve patient outcomes.

RECENT FINDINGS

Emerging therapies are forthcoming in TNBC's treatment landscape, including new post-neoadjuvant chemotherapy strategies, PARP inhibitors, immune checkpoint inhibitors, and antibody-drug conjugates. Combination of different therapies such as AKT/PI3K/mTOR-inhibitors, other immunotherapeutic agents, CDK-inhibitors, antiandrogens, antiangiogenics, and histone deacetylase inhibitors is under clinical investigation. The treatment landscape for TNBC is gradually evolving towards a more personalized approach with promising expectations.

Clinical Activity and Safety of Cediranib and Olaparib Combination in Patients with Metastatic Pancreatic Ductal Adenocarcinoma without BRCA Mutation

Lessons Learned

Cediranib and olaparib combination did not result in clinically meaningful activity in patients with metastatic pancreatic ductal adenocarcinoma without known BRCA mutation.

Background

Cediranib, a vascular endothelial growth factor receptor inhibitor, suppresses expression of BRCA1/2 and RAD51 inducing homologous recombination DNA repair deficiency (HRD) in several cancer cell lines and xenograft models [1]. Olaparib provides a clinical benefit in patients with metastatic pancreatic adenocarcinoma (mPDAC) with germline BRCA mutation (gBRCAmt) [2]. We hypothesized that cediranib induces HRD in the absence of gBRCAmt and synergizes with olaparib, resulting in an objective response in patients with mPDAC.

Methods

Patients with mPDAC with at least one prior systemic chemotherapy were enrolled. Patients with known gBRCAmt were excluded. Patients took cediranib 30 mg daily and olaparib 200 mg twice daily, orally. The primary endpoint was objective response (OR) rate.

Results

Nineteen patients received the study drugs. Seven patients came off treatment before the first restaging scan: six because of clinical progression and one because of an adverse event. No OR was observed. Six patients had stable disease (SD) as a best overall response. The median duration of SD was 3.1 months. The median overall survival was 3.4 months. Common treatment‐related adverse events were fatigue, hypertension, and diarrhea.

Conclusion

Cediranib and olaparib combination did not result in clinically meaningful activity in patients with mPDAC without gBRCAmt.

Leveraging microenvironmental synthetic lethalities to treat cancer

Treatment resistance leads to cancer patient mortality. Therapeutic approaches that employ synthetic lethality to target mutational vulnerabilities in key tumor cell signaling pathways have proven effective in overcoming therapeutic resistance in some cancers. Yet, tumors are organs composed of malignant cells residing within a cellular and noncellular stroma. Tumor evolution and resistance to anticancer treatment are mediated through a dynamic and reciprocal dialogue with the tumor microenvironment (TME). Accordingly, expanding tumor cell synthetic lethality to encompass contextual synthetic lethality has the potential to eradicate tumors by targeting critical TME circuits that promote tumor progression and therapeutic resistance. In this Review, we summarize current knowledge about the TME and discuss its role in treatment. We outline the concept of tumor cell-specific synthetic lethality and describe therapeutic approaches to expand this paradigm to leverage TME synthetic lethality to improve cancer therapy.

Testicular Germ Cell Tumors Acquire Cisplatin Resistance by Rebalancing the Usage of DNA Repair Pathways

Simple Summary

Germ cell tumors are a model of curable solid tumors due to their unique sensitivity to cisplatin-based chemotherapy. Patients are typically young adults, and despite high cure rate, about 20% of them do not achieve remission or relapse, and 50% of them succumb to the disease. The mechanisms behind their resistance to therapy are largely unknown. By using Testicular Germ Cell Tumor (TGCT) cell lines as a model, we investigated the mechanism of acquired resistance to cisplatin. We demonstrated that resistance occurred by a fine modulation of the DNA repair pathway choice. Namely, in resistant cells, repair of double-strand breaks by non-homologous end joining was dampened by the reduced expression of TP53-binding protein 1 (53BP1) and DNA-dependent protein kinase (DNA-PKcs). However, cisplatin-induced damage was repaired efficiently by homologous recombination. Additionally, we demonstrate that pharmacological inhibition of poly (ADP-ribose) polymerase (PARP) combined with cisplatin had an additive/synergistic effect on cisplatin-resistant cells, which represents the proof of concept for introducing PARP inhibitors in salvage therapy.

Abstract

Despite germ cell tumors (GCTs) responding to cisplatin-based chemotherapy at a high rate, a subset of patients does not respond to treatment and have significantly worse prognosis. The biological mechanisms underlying the resistance remain unknown. In this study, by using two TGCT cell lines that have acquired cisplatin resistance after chronic exposure to the drug, we identified some key proteins and mechanisms of acquired resistance. We show that cisplatin-resistant cell lines had a non-homologous end-joining (NHEJ)-less phenotype. This correlated with a reduced basal expression of TP53-binding protein 1 (53BP1) and DNA-dependent protein kinase (DNA-PKcs) proteins and reduced formation of 53BP1 foci after cisplatin treatment. Consistent with these observations, modulation of 53BP1 protein expression altered the cell line’s resistance to cisplatin, and inhibition of DNA-PKcs activity antagonized cisplatin cytotoxicity. Dampening of NHEJ was accompanied by a functional increase in the repair of DNA double-strand breaks (DSBs) by the homologous recombination repair pathway. As a result, cisplatin-resistant cells were more resistant to PARP inhibitor (PARPi) monotherapy. Moreover, when PARPi was given in combination with cisplatin, it exerted an additive/synergistic effect, and reduced the cisplatin dose for cytotoxicity. These results suggest that treatment of cisplatin-refractory patients may benefit from low-dose cisplatin therapy combined with PARPi.

Impact of hypoxia on DNA repair and genome integrity

Hypoxia is a hallmark of the tumour microenvironment with profound effects on tumour biology, influencing cancer progression, the development of metastasis and patient outcome. Hypoxia also contributes to genomic instability and mutation frequency by inhibiting DNA repair pathways. This review summarises the diverse mechanisms by which hypoxia affects DNA repair, including suppression of homology-directed repair, mismatch repair and base excision repair. We also discuss the effects of hypoxia mimetics and agents that induce hypoxia on DNA repair, and we highlight areas of potential clinical relevance as well as future directions.

PARP Inhibitors in Triple-Negative Breast Cancer Including Those With BRCA Mutations

ABSTRACT

Poly(ADP-ribose) polymerase (PARP) is involved in single-strand DNA break base excision repair. PARP inhibition causes synthetic lethality in breast cancers associated with germline BRCA1 and BRCA2 mutations and is routinely used in clinical practice for metastatic breast cancer. Breast cancers with homologous recombination deficiency or BRCAness, most commonly triple-negative breast cancers, may also benefit. Currently, PARP inhibitor use for triple-negative breast cancer with wild-type BRCA does not have definitive efficacy; however, this is an area of active research. Further clinical and translational data may identify additional patient populations that will benefit from PARP inhibitor therapy.

Rh(III)-Catalyzed N-Nitroso Directed C-H Arylation for Facile Construction of Diverse N-Hetero Biaryl Compounds

A Rh(III)-catalyzed C-H arylation reaction of N-nitrosoanilines has been developed in which arylboronic acids were used as arylation reagents. It provides an efficient strategy for the synthesis of N-nitroso-[1,1'-biphenyl]-2-amine, which is an important starting material for the synthesis of N-hetero biaryl compounds, such as 2-amine-1,1'-biphenyl, carbazole, phenanthridone. This protocol can be applied to various N-alkyl substituted N-nitrosoanilines and N-nitrosoanilines with substituents on the phenyl ring. Arylboronic acids with both electron-donating and electron-withdrawing groups are tolerated.

Combination of gefitinib and olaparib versus gefitinib alone in EGFR mutant non-small-cell lung cancer (NSCLC): A multicenter, randomized phase II study (GOAL)

OBJECTIVES

Progression-free survival (PFS) and response rate to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) varies in patients with non-small-cell lung cancer (NSCLC) driven byEGFR mutations, suggesting that other genetic alterations may influence oncogene addiction. Low BRCA1 mRNA levels correlate with longer PFS in erlotinib-treated EGFR-mutant NSCLC patients. Since the poly (ADP-ribose) polymerase (PARP) inhibitor, olaparib, may attenuate and/or prevent BRCA1 expression, the addition of olaparib to gefitinib could improve outcome in EGFR-mutant advanced NSCLC.

MATERIALS AND METHODS

GOAL was a multicenter, randomized phase IB/II study performed in two countries, Spain and Mexico. Eligible patients were 18 years or older, treatment-naïve, pathologically confirmed stage IV NSCLC, with centrally confirmed EGFR mutations and measurable disease. Patients were randomly allocated (1:1) to receive gefitinib 250 mg daily or gefitinib 250 mg daily plus olaparib 200 mg three times daily in 28-day cycles. The primary endpoint was PFS. Secondary endpoints included overall survival (OS), response rate, safety and tolerability.

RESULTS

Between September 2013, and July 2016, 182 patients underwent randomization, 91 received gefitinib and 91 received gefitinib plus olaparib. There were no differences in gender, age, smoking status, performance status, presence of bone and brain metastases or type ofEGFR mutation. Median PFS was 10.9 months (95 % CI 9.3-13.3) in the gefitinib arm and 12.8 months (95 % CI 9.1-14.7) in the gefitinib plus olaparib arm (HR 1.38, 95 % CI 1.00-1.92; p = 0.124). The most common adverse events were anemia, 78 % in gefitinib plus olaparib group, 38 % in gefitinib arm, diarrhea, 65 % and 60 %, and fatigue, 40 % and 32 %, respectively.

CONCLUSIONS

The gefitinib plus olaparib combination did not provide significant benefit over gefitinib alone. The combination's safety profile showed an increase in hematological and gastrointestinal toxicity, compared to gefitinib alone, however, no relevant adverse events were noted.

Application and reflection of genomic scar assays in evaluating the efficacy of platinum salts and PARP inhibitors in cancer therapy

Defective DNA repair is one of the most important features of tumors. BRCA1/2 participates in homologous recombination repair as a key tumor suppressor gene. BRCA1/2 mutation is an important biomarker for predicting the sensitivity of platinum salts and Poly (ADP-ribose) polymerase (PARP) inhibitors in breast cancer, ovarian cancer, and other cancers. However, epigenetic modifications and other mutations in homologous recombination repair (HRR) genes can also cause homologous recombination deficiency (HRD). Patients with no BRCA1/2 mutations, but bearing similar molecular phenotypes (BRCAness) can still obtain clinical benefits from treatment with platinum salts or PARP inhibitors. Therefore, an accurate assessment of HRD is essential for the formulation of personalized treatments. However, methods to identify HRD in tumors vary and are controversial. Currently, genomic scar assays have been used in multiple clinical trials to assess patient clinical benefit. This review summarizes the therapeutic effects of platinum salts and PARP inhibitors in breast and ovarian cancer, clarifies the predictive value of genomic scar assays in evaluating the clinical benefit of different patient groups and treatment options, and proposes the limitations and optimization of current HRD scoring methods. Using and optimizing genomic scar assays can help to accurately screen the population with the most benefit, expand the scope of drug application, and make the most suitable clinical decision based on individual differences.

Dual inhibition of VEGF and PARP suppresses KRAS-mutant colorectal cancer

The addition of bevacizumab to chemotherapy has prolonged overall and progression-free survival rates for metastatic colorectal cancer (mCRC). However, KRAS-mutant (KRAS-mut) CRC, lacking an ideal targeted agent, represents an inferior-response subgroup of patients. In the present study, we investigated a combination approach of bevacizumab + olaparib in KRAS-mut CRC in a preclinical setting. The combined therapy effectively prevented tumor growth in a KRAS-mut cancer cell-derived xenograft model, although this effect was not observed in vitro. Under bevacizumab treatment, we detected intratumor hypoxia and impaired homologous recombination repair (HRR), accompanied by vascular regression. We explored the underlying mechanism of this combined therapy by mimicking a hypoxic condition in vitro using cobalt chloride (CoCl2). The results showed that hypoxia impairs HRR and therefore sensitized KRAS-mut CRC cell lines HCT-116, SW620, and Lovo to olaparib. Furthermore, under this hypoxic condition, olaparib could arrest the cell cycle in the G2/M phase, increase DNA damage and dramatically induce cell apoptosis in KRAS-mut CRC cells. Taken together, these results indicated that the combination of bevacizumab + olaparib could be a potential therapeutic approach in a KRAS-mut CRC cohort.

Inside the hypoxic tumour: reprogramming of the DDR and radioresistance

The hypoxic tumour is a chaotic landscape of struggle and adaption. Against the adversity of oxygen starvation, hypoxic cancer cells initiate a reprogramming of transcriptional activities, allowing for survival, metastasis and treatment failure. This makes hypoxia a crucial feature of aggressive tumours. Its importance, to cancer and other diseases, was recognised by the award of the 2019 Nobel Prize in Physiology or Medicine for research contributing to our understanding of the cellular response to oxygen deprivation. For cancers with limited treatment options, for example those that rely heavily on radiotherapy, the results of hypoxic adaption are particularly restrictive to treatment success. A fundamental aspect of this hypoxic reprogramming with direct relevance to radioresistance, is the alteration to the DNA damage response, a complex set of intermingling processes that guide the cell (for good or for bad) towards DNA repair or cell death. These alterations, compounded by the fact that oxygen is required to induce damage to DNA during radiotherapy, means that hypoxia represents a persistent obstacle in the treatment of many solid tumours. Considerable research has been done to reverse, correct or diminish hypoxia's power over successful treatment. Though many clinical trials have been performed or are ongoing, particularly in the context of imaging studies and biomarker discovery, this research has yet to inform clinical practice. Indeed, the only hypoxia intervention incorporated into standard of care is the use of the hypoxia-activated prodrug Nimorazole, for head and neck cancer patients in Denmark. Decades of research have allowed us to build a picture of the shift in the DNA repair capabilities of hypoxic cancer cells. A literature consensus tells us that key signal transducers of this response are upregulated, where repair proteins are downregulated. However, a complete understanding of how these alterations lead to radioresistance is yet to come.

Development of new medical treatment for epithelial ovarian cancer recurrence

Epithelial ovarian cancer (EOC) is the scariest gynaecological cancer. Many advances have been done with evolving knowledge, leading to the introduction of new drugs, most in maintenance setting. The antiangiogenic Bevacizumab and the three approved PARP-inhibitors-olaparib, niraparib and rucaparib-are gradually improving PFS of patients with EOC, with initial effects on OS too. But recurrence is still a heavy sentence and lethality continues to be high. Ovarian cancer is a complex disease, with different clinical presentation, histological aspect, and molecular expression, leading to disappointing results, when using a single drug. Implementation of biobanking and analysis of patients' tumour samples, before starting a treatment, could be a promising way to better understand molecular aspects of this disease, to identify markers predictive of response and to allow a better use of experimental drugs, as immunomodulators, targeted therapies, and combinations of these, to fight tumour growth and clinical progression. We reviewed the literature on the updated treatments for recurrent ovarian cancer, summarizing all the available drugs and combinations to treat patients with this diagnosis, and focusing the attention on the new approved molecules and the contemporary Clinical Trials, investigating new target therapies and new associations.

Cediranib suppresses homology-directed DNA repair through down-regulation of BRCA1/2 and RAD51

Combining the anti-angiogenic agent cediranib with the poly(ADP-ribose) polymerase (PARP) inhibitor olaparib improves progression-free survival compared to olaparib alone in ovarian cancer patients through an unknown mechanism. PARP inhibitors are used primarily in the treatment of patients with DNA repair-associated (BRCA1/2) mutated cancers because these mutations cause a deficit in homology-directed DNA repair (HDR) that confers sensitivity to these agents. However, the combination of cediranib and olaparib was effective in patients without BRCA1/2 mutations. We report here that cediranib confers sensitivity to olaparib by down-regulating HDR in tumor cells. This occurs partially as a result of cediranib inducing hypoxia, which suppresses expression of the HDR factors BRCA1/2 and RAD51 recombinase (RAD51). However, we also observed that cediranib has a direct effect on HDR independent of its ability to induce tumor hypoxia. This direct effect occurs through platelet-derived growth factor receptor (PDGFR) inhibition, activation of protein phosphatase 2A (PP2A), and E2F transcription factor 4 (E2F4)/RB transcriptional corepressor like 2 (RB2/p130)-mediated repression of BRCA1/2 and RAD51 gene expression. This down-regulation was seen in mouse tumor xenografts but not in mouse bone marrow, providing a therapeutic window for combining cediranib and olaparib in cancer therapy. Our work reveals a treatment strategy by which DNA repair can be manipulated in human tumors to induce synthetic lethality, broadening the potential therapeutic scope of cediranib based on its activity as a DNA repair inhibitor.

Combination of Withaferin-A and CAPE Provides Superior Anticancer Potency: Bioinformatics and Experimental Evidence to Their Molecular Targets and Mechanism of Action

We have earlier reported anticancer activity in Withaferin A (Wi-A), a withanolide derived from Ashwagandha (Withania somnifera) and caffeic acid phenethyl ester (CAPE), an active compound from New Zealand honeybee propolis. Whereas Wi-A was cytotoxic to both cancer and normal cells, CAPE has been shown to cause selective death of cancer cells. In the present study, we investigated the efficacy of Wi-A, CAPE, and their combination to ovarian and cervical cancer cells. Both Wi-A and CAPE were seen to activate tumor suppressor protein p53 by downregulation of mortalin and abrogation of its interactions with p53. Downregulation of mortalin translated to compromised mitochondria integrity and function that affected poly ADP-ribose polymerase1 (PARP1); a key regulator of DNA repair and protein-target for Olaparib, drugs clinically used for treatment of breast, ovarian and cervical cancers)-mediated DNA repair yielding growth arrest or apoptosis. Furthermore, we also compared the docking capability of Wi-A and CAPE to PARP1 and found that both of these could bind to the catalytic domain of PARP1, similar to Olaparib. We provide experimental evidences that (i) Wi-A and CAPE cause inactivation of PARP1-mediated DNA repair leading to accumulation of DNA damage and activation of apoptosis signaling by multiple ways, and (ii) a combination of Wi-A and CAPE offers selective toxicity and better potency to cancer cells.

PARP inhibitor combinations in prostate cancer

Polyadenosine-diphosphate-ribose polymerase (PARP) inhibitors cause deoxyribonucleic acid (DNA) damage that can be lethal to cells with deficient repair mechanisms. A number of PARP inhibitors are being tested as treatments for men with prostate cancer, both as monotherapies and in combinations that are based on purported synergies in treatment effect. While the initial single-agent development focused on men with identified deficiencies in DNA-repair pathways, broader patient populations are being considered for combination approaches. This review summarizes the current clinical development of PARP inhibitors and explores the rationale for novel combination strategies.