Sensitization of colorectal cancer to irinotecan therapy by PARP inhibitor rucaparib

Synthetic Lethality Beyond BRCA: A Phase I Study of Rucaparib and Irinotecan in Metastatic Solid Tumors With Homologous Recombination-Deficiency Mutations Beyond BRCA1/2

PURPOSE

Combining poly ADP-ribose polymerase (PARP) and topoisomerase I inhibitors has demonstrated synergistic effects in in vivo models. This phase I trial evaluated rucaparib and irinotecan in metastatic solid tumors with homologous recombination deficiency.

METHODS

This study enrolled patients in three cohorts to determine the tolerability and preliminary efficacy of (1) rucaparib 400 mg PO twice a day (days 1-7, 15-21) and irinotecan 65 mg/m2 intravenously once every 2 weeks; (2) rucaparib 400 mg PO twice a day (D1-7, 15-21) and irinotecan 100 mg/m2 once every 2 weeks; and (3) rucaparib 400 mg per os twice a day (D1-7) and irinotecan 100 mg/m2 once every 3 weeks.

RESULTS

Twenty patients were enrolled: 95% with previous platinum, 40% with previous irinotecan, and 20% with previous PARP inhibitor. The maximally tolerated was determined as rucaparib 400 mg twice a day days 1-7 and irinotecan 100 mg/m2 once every 3 weeks. Four dose-limiting toxicities (all grade 3-4 neutropenia) occurred during dose escalation with only neutropenia as other grade 3-4 toxicities (25%; grade 3 [n = 3], grade 4 [n = 2]). Treatment-related grade 1-2 adverse events included neutropenia (45%), diarrhea (45%), nausea (40%), and fatigue (30%). Of 17 patients with evaluable disease, six patients (35%) derived clinical benefit (n = 2 with PR, n = 4 with stable disease for over 6 months). Three patients remained on study >1 year: two with ATM mutations (small bowel carcinoma and pancreatic neuroendocrine tumor) and one patient with a PALB2 mutation (primary peritoneal cancer).

CONCLUSION

Pulse dosing of rucaparib and once every 3 weeks irinotecan was well tolerated for up to 18 months with durable responses in BRCA-, PALB2-, and ATM-mutated cancers despite progression on previous platinum.

ADP-ribosylation: An emerging direction for disease treatment

ADP-ribosylation (ADPr) is a dynamically reversible post-translational modification (PTM) driven primarily by ADP-ribosyltransferases (ADPRTs or ARTs), which have ADP-ribosyl transfer activity. ADPr modification is involved in signaling pathways, DNA damage repair, metabolism, immunity, and inflammation. In recent years, several studies have revealed that new targets or treatments for tumors, cardiovascular diseases, neuromuscular diseases and infectious diseases can be explored by regulating ADPr. Here, we review the recent research progress on ART-mediated ADP-ribosylation and the latest findings in the diagnosis and treatment of related diseases.

PARP Inhibitors in Colorectal Malignancies: A 2023 Update

BACKGROUND

Colorectal carcinoma (CRC) is one of the most common malignancies in the Western world, and metastatic disease is associated with a dismal prognosis. Poly-ADpribose polymerase (PARP) inhibitors gain increasing attention in the field of medical oncology, as they lead to synthetic lethality in malignancies with preexisting alterations in the DNA damage repair (DDR) pathway. As those alterations are frequently seen in CRC, a targeted approach through PARP inhibitors is expected to benefit these patients, both alone and in combination with other agents like chemotherapy, immunotherapy, antiangiogenics, and radiation.

OBJECTIVE

This review article aims to better clarify the role of PARP inhibitors as a treatment option in patients with metastatic CRC with alterations in the DDR pathway.

METHODS

We used the PubMed database to retrieve journal articles and the inclusion criteria were all human studies that illustrated the effective role of PARP inhibitors in patients with metastatic CRC with homologous repair deficiency (HRD) and the correct line of therapy.

RESULTS

Current evidence supports the utilization of PARP inhibitors in CRC subgroups, as monotherapy and in combination with other agents. Up to now, data are insufficient to support a formal indication, and further research is needed.

CONCLUSION

Efforts to precisely define the homologous repair deficiency (HRD) in CRC - and eventually the subgroup of patients that are expected to benefit the most - are also underway.

Polyadenosine diphosphate-ribose polymerase inhibitors: advances, implications, and challenges in tumor radiotherapy sensitization

Polyadenosine diphosphate-ribose polymerase (PARP) is a key modifying enzyme in cells, which participates in single-strand break repair and indirectly affects double-strand break repair. PARP inhibitors have shown great potential in oncotherapy by exploiting DNA damage repair pathways, and several small molecule PARP inhibitors have been approved by the U.S. Food and Drug Administration for treating various tumor types. PARP inhibitors not only have significant antitumor effects but also have some synergistic effects when combined with radiotherapy; therefore they have potential as radiation sensitizers. Here, we reviewed the advances and implications of PARP inhibitors in tumor radiotherapy sensitization. First, we summarized the multiple functions of PARP and the mechanisms by which its inhibitors exert antitumor effects. Next, we discuss the immunomodulatory effects of PARP and its inhibitors in tumors. Then, we described the theoretical basis of using PARP inhibitors in combination with radiotherapy and outlined their importance in oncological radiotherapy. Finally, we reviewed the current challenges in this field and elaborated on the future applications of PARP inhibitors as radiation sensitizers. A comprehensive understanding of the mechanism, optimal dosing, long-term safety, and identification of responsive biomarkers remain key challenges to integrating PARP inhibition into the radiotherapy management of cancer patients. Therefore, extensive research in these areas would facilitate the development of precision radiotherapy using PARP inhibitors to improve patient outcomes.

Identification of disulfidptosis-related subtypes, characterization of tumor microenvironment infiltration, and development of a prognosis model in colorectal cancer

BACKGROUND

Colorectal cancer is the second leading cause of cancer-related deaths, which imposes a significant societal burden. Regular screening and emerging molecular tumor markers have important implications for detecting the progression and development of colorectal cancer. Disulfidptosis is a newly defined type of programmed cell death triggered by abnormal accumulation of disulfide compounds in cells that stimulate disulfide stress. Currently, there is no relevant discussion on this mechanism and colorectal cancer.

METHODS

We classified the disulfidptosis-related subtypes of colorectal cancer using bioinformatics methods. Through secondary clustering of differentially expressed genes between subtypes, we identified characteristic genes of the disulfidptosis subtype, constructed a prognostic model, and searched for potential biomarkers through clinical validation.

RESULTS

Using disulfidptosis-related genes collected from the literature, we classified colorectal cancer patients from public databases into three subtypes. The differentially expressed genes between subtypes were clustered into three gene subtypes, and eight characteristic genes were screened to construct a prognostic model.

CONCLUSION

The disulfidptosis mechanism has important value in the classification of colorectal cancer patients, and characteristic genes selected based on this mechanism can serve as a new potential biological marker for colorectal cancer.

A carrier-free supramolecular nano-twin-drug for overcoming irinotecan-resistance and enhancing efficacy against colorectal cancer

Irinotecan (Ir) is commonly employed as a first-line chemotherapeutic treatment for colorectal cancer (CRC). However, tremendous impediments remain to be addressed to surmount drug resistance and ameliorate adverse events. Poly-ADP-Ribose Polymerase (PARP) participates in the maintenance of genome stability and the repair of DNA damage, thus playing a critical role in chemotherapy resistance. In this work, we introduce a novel curative strategy that utilizes nanoparticles (NPs) prepared by dynamic supramolecular co-assembly of Ir and a PARP inhibitor (PARPi) niraparib (Nir) through π-π stacking and hydrogen bond interactions. The Ir and Nir self-assembled Nano-Twin-Drug of (Nir-Ir NPs) could enhance the therapeutic effect on CRC by synergistically inhibiting the DNA damage repair pathway and activating the tumor cell apoptosis process without obvious toxicity. In addition, the Nir-Ir NPs could effectively reverse irinotecan-resistance by inhibiting the expression of multiple resistance protein-1 (MRP-1). Overall, our study underscores the distinctive advantages and potential of Nir-Ir NPs as a complementary strategy to chemotherapy by simultaneously overcoming the Ir resistance and improving the anti-tumor efficacy against CRC.

Alkylation of nucleobases by 2-chloro-N,N-diethylethanamine hydrochloride (CDEAH) sensitizes PARP1-deficient tumors

Targeting BRCA1- and BRCA2-deficient tumors through synthetic lethality using poly(ADP-ribose) polymerase inhibitors (PARPi) has emerged as a successful strategy for cancer therapy. PARPi monotherapy has shown excellent efficacy and safety profiles in clinical practice but is limited by the need for tumor genome mutations in BRCA or other homologous recombination genes as well as the rapid emergence of resistance. In this study, we identified 2-chloro-N,N-diethylethanamine hydrochloride (CDEAH) as a small molecule that selectively kills PARP1- and xeroderma pigmentosum A-deficient cells. CDEAH is a monofunctional alkylating agent that preferentially alkylates guanine nucleobases, forming DNA adducts that can be removed from DNA by either a PARP1-dependent base excision repair or nucleotide excision repair. Treatment of PARP1-deficient cells leads to the formation of strand breaks, an accumulation of cells in S phase and activation of the DNA damage response. Furthermore, CDEAH selectively inhibits PARP1-deficient xenograft tumor growth compared to isogenic PARP1-proficient tumors. Collectively, we report the discovery of an alkylating agent inducing DNA damage that requires PARP1 activity for repair and acts synergistically with PARPi.

Anti-Colorectal Cancer Effects of a Novel Camptothecin Derivative PCC0208037 In Vitro and In Vivo

Colorectal cancer is one of the most common malignancies, and the topoisomerase inhibitor irinotecan (CPT-11)-based chemotherapeutic regimen is currently the first-line treatment with impressive therapeutic efficacy. However, irinotecan has several clinically significant side effects, including diarrhea, which limit its clinical utility and efficacy in many patients. In an effort to discover better and improved pharmacotherapy against colorectal cancer, we synthesized a novel topoisomerase inhibitor, PCC0208037, examined its anti-tumor efficacy and related molecular mechanisms, and characterized its toxicity and pharmacokinetic profiles. PCC0208037 suppressed colorectal cancer cell (CRC) proliferation and increased cell cycle arrest, which may be related to its effects on up-regulating DNA damage response (DDR)-related molecules and apoptosis-related proteins. PCC0208037 demonstrated robust anti-tumor activity in vivo in a colorectal cancer cell xenograft model, which was comparable to or slightly better than CPT-11. In a preliminary toxicology study, PCC0208037 demonstrated much weaker tissue damage to colorectal tissue than CPT-11, and its impacts on food intake and body weight loss were more transient and recovered faster than CPT-11 in mice. This could be partially explained by the pharmacokinetic findings, which showed that PCC0208037 and its active metabolite, SN-38, were more accumulated in tumor tissue than in the intestine, as compared to CPT-11. Taken together, these results described a novel Topo I inhibitor with a comparative advantage over the standard treatment of colorectal cancer CPT-11 and could be a promising candidate compound for the treatment of colorectal cancer that warrants further investigation.

Novel Set of Diarylmethanes to Target Colorectal Cancer: Synthesis, In Vitro and In Silico Studies

Distinctive structural, chemical, and physical properties make the diarylmethane scaffold an essential constituent of many active biomolecules nowadays used in pharmaceutical, agrochemical, and material sciences. In this work, 33 novel diarylmethane molecules aiming to target colorectal cancer were designed. Two series of functionalized olefinic and aryloxy diarylmethanes were synthesized and chemically characterized. The synthetic strategy of olefinic diarylmethanes involved a McMurry cross-coupling reaction as key step and the synthesis of aryloxy diarylmethanes included an O-arylation step. A preliminarily screening in human colorectal cancer cells (HT-29 and HCT116) and murine primary fibroblasts (L929) allowed the selection, for more detailed analyses, of the three best candidates (10a, 10b and 12a) based on their high inhibition of cancer cell proliferation and non-toxic effects on murine fibroblasts (<100 µM). The anticancer potential of these diarylmethane compounds was then assessed using apoptotic (phospho-p38) and anti-apoptotic (phospho-ERK, phospho-Akt) cell survival signaling pathways, by analyzing the DNA fragmentation capacity, and through the caspase-3 and PARP cleavage pro-apoptotic markers. Compound 12a (2-(1-(4-methoxyphenyl)-2-(4-(trifluoromethyl)phenyl) vinyl) pyridine, Z isomer) was found to be the most active molecule. The binding mode to five biological targets (i.e., AKT, ERK-1 and ERK-2, PARP, and caspase-3) was explored using molecular modeling, and AKT was identified as the most interesting target. Finally, compounds 10a, 10b and 12a were predicted to have appropriate drug-likeness and good Absorption, Distribution, Metabolism and Excretion (ADME) profiles.

Potentiating effect of reovirus on immune checkpoint inhibition in microsatellite stable colorectal cancer

The majority of colorectal cancers (CRCs) are microsatellite stable (MSS) and resistant to immunotherapy. The current study explores the possibility of using oncolytic reovirus to sensitize MSS CRC to immune checkpoint inhibition. While reovirus reduced metabolic activity among KRAS Mut cells, microarray/computational analysis revealed microsatellite status-oriented activation of immune-response pathways. Reovirus plus anti-PD-1 treatment increased cell death among MSS cells ex vivo. Reduced tumorigenicity and proliferative index, and increased apoptosis were evident among CT26 [MSS, KRAS Mut], but not in MC38 [microsatellite unstable/MSI, KRAS Wt] syngeneic mouse models under combinatorial treatment. PD-L1-PD-1 signaling axis were differentially altered among CT26/MC38 models. Combinatorial treatment activated the innate immune system, pattern recognition receptors, and antigen presentation markers. Furthermore, we observed the reduction of immunosuppressive macrophages and expansion of effector T cell subsets, as well as reduction in T cell exhaustion. The current investigation sheds light on the immunological mechanisms of the reovirus-anti-PD-1 combination to reduce the growth of MSS CRC.

MCC Gene Silencing Is a CpG Island Methylator Phenotype-Associated Factor That Predisposes Colon Cancer Cells to Irinotecan and Olaparib

Simple Summary

DNA hypermethylation of specific regulatory regions causes gene silencing that is an important cancer-promoting mechanism. A subset of colorectal cancers display concordant hypermethylation and silencing of multiple genes, and this appears to change the way in which tumors respond to some cancer therapies. The aim of this study was to evaluate how the presence of the MCC gene silencing relates to the highly methylated subset of colorectal cancers and how it may affect therapy responsiveness. We found that strong MCC silencing is found throughout the hypermethylated subset, but MCC expression is also lost or reduced in some other tumors which show hypomethylated regions of the gene. In cell culture experiments, the deletion of MCC increased the responsiveness of cancer cells to the chemotherapy drug irinotecan (SN38), and this was further augmented by a targeted cancer drug, the PARP-inhibitor Olaparib.

Abstract

Chemotherapy is a mainstay of colorectal cancer treatment, and often involves a combination drug regime. CpG island methylator phenotype (CIMP)-positive tumors are potentially more responsive to the topoisomerase-inhibitor irinotecan. The mechanistic basis of the increased sensitivity of CIMP cancers to irinotecan is poorly understood. Mutated in Colorectal Cancer (MCC) is emerging as a multifunctional tumor suppressor gene in colorectal and liver cancers, and has been implicated in drug responsiveness. Here, we found that CIMP tumors undergo MCC loss almost exclusively via promoter hypermethylation rather than copy number variation or mutations. A subset of cancers display hypomethylation which is also associated with low MCC expression, particularly in rectal cancer, where CIMP is rare. MCC knockdown or deletion was found to sensitize cells to SN38 (the active metabolite of irinotecan) or the PARP-inhibitor Olaparib. A synergistic effect on cell death was evident when these drugs were used concurrently. The improved SN38/irinotecan efficacy was accompanied by the down-regulation of DNA repair genes. Thus, differential methylation of MCC is potentially a valuable biomarker to identify colorectal cancers suitable for irinotecan therapy, possibly in combination with PARP inhibitors.

A Prognostic Gene Signature for Hepatocellular Carcinoma

Hepatocellular carcinoma is the third most common cause of cancer-related deaths in China and immune-based therapy can improve patient outcomes. In this study, we investigated the relationship between immunity-associated genes and hepatocellular carcinoma from the prognostic perspective. The data downloaded from The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) and the Gene Expression Omnibus (GEO) was screened for gene mutation frequency using the maftools package. Immunity-associated eight-gene signature with strong prognostic ability was constructed and proved as an independent predictor of the patient outcome in LIHC. Seven genes in the immune-related eight-gene signature were strongly associated with the infiltration of M0 macrophages, resting mast cells, and regulatory T cells. Our research may provide clinicians with a quantitative method to predict the prognosis of patients with liver cancer, which can assist in the selection of the optimal treatment plan.

Targeting the DNA Damage Response Pathway as a Novel Therapeutic Strategy in Colorectal Cancer

Simple Summary

Defective DNA damage response (DDR) is a hallmark of cancer leading to genomic instability. Up to 15–20% of colorectal cancers carry alterations in DDR. However, the role of DDR alterations as a prognostic factor and as a therapeutic target must be elucidated. To date, disappointing results have been obtained in different clinical trials mainly due to poor molecular selection of patients. Several challenges must be overcome before these compounds may have an impact on colorectal cancer. For instance, although some preclinical evidence showed the vulnerability of a subset of CRCs to PARP inhibitors, no specific clinical or molecular biomarkers have been validated to select patients. Moreover, different DDR alterations may not equally confer platinum sensitivity in CRC patients. Further efforts are needed in both preclinical and clinical settings to exploit DDR alterations as therapeutic targets and to eventually discover PARP or other DDR inhibitors (e.g., Wee1) with clinical benefit on colorectal cancer patients.

Abstract

Major advances have been made in CRC treatment in recent years, especially in molecularly driven therapies and immunotherapy. Despite this, a large number of advanced colorectal cancer patients do not benefit from these treatments and their prognosis remains poor. The landscape of DNA damage response (DDR) alterations is emerging as a novel target for treatment in different cancer types. PARP inhibitors have been approved for the treatment of ovarian, breast, pancreatic, and prostate cancers carrying deleterious BRCA1/2 pathogenic variants or homologous recombination repair (HRR) deficiency (HRD). Recent research reported on the emerging role of HRD in CRC and showed that alterations in these genes, either germline or somatic, are carried by up to 15–20% of CRCs. However, the role of HRD is still widely unknown, and few data about their clinical impact are available, especially in CRC patients. In this review, we report preclinical and clinical data currently available on DDR inhibitors in CRC. We also emphasize the predictive role of DDR mutations in response to platinum-based chemotherapy and the potential clinical role of DDR inhibitors. More preclinical and clinical trials are required to better understand the impact of DDR alterations in CRC patients and the therapeutic opportunities with novel DDR inhibitors.

Peroxidase from foxtail millet bran exerts anti-colorectal cancer activity via targeting cell-surface GRP78 to inactivate STAT3 pathway

Molecular targeted therapy has become an emerging promising strategy in cancer treatment, and screening the agents targeting at cancer cell specific targets is very desirable for cancer treatment. Our previous study firstly found that a secretory peroxidase of class III derived from foxtail millet bran (FMBP) exhibited excellent targeting anti-colorectal cancer (CRC) activity in vivo and in vitro, whereas its underlying target remains unclear. The highlight of present study focuses on the finding that cell surface glucose-regulated protein 78 (csGRP78) abnormally located on CRC is positively correlated with the anti-CRC effects of FMBP, indicating it serves as a potential target of FMBP against CRC. Further, we demonstrated that the combination of FMBP with the nucleotide binding domain (NBD) of csGRP78 interfered with the downstream activation of signal transducer and activator of transcription 3 (STAT3) in CRC cells, thus promoting the intracellular accumulation of reactive oxygen species (ROS) and cell grown inhibition. These phenomena were further confirmed in nude mice tumor model. Collectively, our study highlights csGRP78 acts as an underlying target of FMBP against CRC, uncovering the clinical potential of FMBP as a targeted agent for CRC in the future.

Insight Into Nicotinamide Adenine Dinucleotide Homeostasis as a Targetable Metabolic Pathway in Colorectal Cancer

Tumour cells modify their cellular metabolism with the aim to sustain uncontrolled proliferation. Cancer cells necessitate adequate amounts of NAD and NADPH to support several enzymes that are usually overexpressed and/or overactivated. Nicotinamide adenine dinucleotide (NAD) is an essential cofactor and substrate of several NAD-consuming enzymes, such as PARPs and sirtuins, while NADPH is important in the regulation of the redox status in cells. The present review explores the rationale for targeting the key enzymes that maintain the cellular NAD/NADPH pool in colorectal cancer and the enzymes that consume or use NADP(H).

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.

Poly adenosine diphosphate-ribosylation, a promising target for colorectal cancer treatment

The development of colorectal cancer (CRC) can result from changes in a variety of cellular systems within the tumor microenvironment. Particularly, it is primarily associated with genomic instability that is the gradual accumulation of genetic and epigenetic changes consisting of a characteristic set of mutations crucial for pathways in CRC progression. Based on this background, the potential to focus on poly [adenosine diphosphate (ADP)-ribose] polymerase (PARP)-1 and poly-ADP ribosylation (PARylation) as the main causes of malignant formation of CRC may be considered. One of the important functions of PARP-1 and PARylation is its deoxyribonucleic acid (DNA) repair function, which plays a pivotal role in the DNA damage response and prevention of DNA damage maintaining the redox homeostasis involved in the regulation of oxidation and superoxide. PARP-1 and PARylation can also alter epigenetic markers and chromatin structure involved in transcriptional regulation for the oncogenes or tumor suppressor genes by remodeling histone and chromatin enzymes. Given the high importance of these processes in CRC, it can be considered that PARP-1 and PARylation are at the forefront of the pathological changes required for CRC progression. Therefore, this review addresses the current molecular biological features for understanding the multifactorial function of PARP-1 and PARylation in CRC related to the aforementioned roles; furthermore, it presents a summary of recent approaches with PARP-1 inhibition in non-clinical and clinical studies targeting CRC. This understanding could help embrace the importance of targeting PARP-1 and PARylation in the treatment of CRC, which may present the potential to identify various research topics that can be challenged both non-clinically and clinically.

Poly adenosine diphosphate-ribosylation, a promising target for colorectal cancer treatment

The development of colorectal cancer (CRC) can result from changes in a variety of cellular systems within the tumor microenvironment. Particularly, it is primarily associated with genomic instability that is the gradual accumulation of genetic and epigenetic changes consisting of a characteristic set of mutations crucial for pathways in CRC progression. Based on this background, the potential to focus on poly [adenosine diphosphate (ADP)-ribose] polymerase (PARP)-1 and poly-ADP ribosylation (PARylation) as the main causes of malignant formation of CRC may be considered. One of the important functions of PARP-1 and PARylation is its deoxyribonucleic acid (DNA) repair function, which plays a pivotal role in the DNA damage response and prevention of DNA damage maintaining the redox homeostasis involved in the regulation of oxidation and superoxide. PARP-1 and PARylation can also alter epigenetic markers and chromatin structure involved in transcriptional regulation for the oncogenes or tumor suppressor genes by remodeling histone and chromatin enzymes. Given the high importance of these processes in CRC, it can be considered that PARP-1 and PARylation are at the forefront of the pathological changes required for CRC progression. Therefore, this review addresses the current molecular biological features for understanding the multifactorial function of PARP-1 and PARylation in CRC related to the aforementioned roles; furthermore, it presents a summary of recent approaches with PARP-1 inhibition in non-clinical and clinical studies targeting CRC. This understanding could help embrace the importance of targeting PARP-1 and PARylation in the treatment of CRC, which may present the potential to identify various research topics that can be challenged both non-clinically and clinically.

The attributes of plakins in cancer and disease: perspectives on ovarian cancer progression, chemoresistance and recurrence

The plakin family of cytoskeletal proteins play an important role in cancer progression yet are under-studied in cancer, especially ovarian cancer. These large cytoskeletal proteins have primary roles in the maintenance of cytoskeletal integrity but are also associated with scaffolds of intermediate filaments and hemidesmosomal adhesion complexes mediating signalling pathways that regulate cellular growth, migration, invasion and differentiation as well as stress response. Abnormalities of plakins, and the closely related spectraplakins, result in diseases of the skin, striated muscle and nervous tissue. Their prevalence in epithelial cells suggests that plakins may play a role in epithelial ovarian cancer progression and recurrence. In this review article, we explore the roles of plakins, particularly plectin, periplakin and envoplakin in disease-states and cancers with emphasis on ovarian cancer. We discuss the potential role the plakin family of proteins play in regulating cancer cell growth, survival, migration, invasion and drug resistance. We highlight potential relationships between plakins, epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) and discuss how interaction of these processes may affect ovarian cancer progression, chemoresistance and ultimately recurrence. We propose that molecular changes in the expression of plakins leads to the transition of benign ovarian tumours to carcinomas, as well as floating cellular aggregates (commonly known as spheroids) in the ascites microenvironment, which may contribute to the sustenance and progression of the disease. In this review, attempts have been made to understand the crucial changes in plakin expression in relation to progression and recurrence of ovarian cancer.

Cytoplasmic ADP-ribosylation levels correlate with markers of patient outcome in distinct human cancers

ADP-ribosylation (ADPR) is a posttranslational modification whose importance in oncology keeps increasing due to frequent use of PARP inhibitors (PARPi) to treat different tumor types. Due to the lack of suitable tools to analyze cellular ADPR levels, ADPR's significance for cancer progression and patient outcome is unclear. In this study, we assessed ADPR levels by immunohistochemistry using a newly developed anti-ADP-ribose (ADPr) antibody, which is able to detect both mono- and poly-ADPR. Tissue microarrays containing brain (n = 103), breast (n = 1108), colon (n = 236), lung (n = 138), ovarian (n = 142), and prostate (n = 328) cancers were used to correlate ADPR staining intensities to clinico-pathological data, including patient overall survival (OS), tumor grade, tumor stage (pT), lymph node status (pN), and the presence of distant metastasis (pM). While nuclear ADPR was detected only in a minority of the samples, cytoplasmic ADPR (cyADPR) staining was observed in most tumor types. Strong cyADPR intensities were significantly associated with better overall survival in invasive ductal breast cancer (p < 0.0001), invasive lobular breast cancer (p < 0.005), and high grade serous ovarian cancer patients (p < 0.01). Furthermore, stronger cytoplasmic ADPR levels significantly correlated with early tumor stage in colorectal and in invasive ductal breast adenocarcinoma (p < 0.0001 and p < 0.01, respectively) and with the absence of regional lymph node metastasis in colorectal adenocarcinoma (p < 0.05). No correlation to cyADPR was found for prostate and lung cancer or brain tumors. In conclusion, our new anti-ADP-ribose antibody revealed heterogeneous ADPR staining patterns with predominant cytoplasmic ADPR staining in most tumor types. Different cyADPR staining patterns could help to better understand variable response rates to PARP inhibitors in the future.

Molecular correlates of sensitivity to PARP inhibition beyond homologous recombination deficiency in pre-clinical models of colorectal cancer point to wild-type TP53 activity

BACKGROUND

PARP inhibitors are active in various tumour types beyond BRCA-mutant cancers, but their activity and molecular correlates in colorectal cancer (CRC) are not well studied.

METHODS

Mutations and genome-wide mutational patterns associated with homologous recombination deficiency (HRD) were investigated in 255 primary CRCs with whole-exome sequencing and/or DNA copy number data. Efficacy of five PARP inhibitors and their molecular correlates were evaluated in 93 CRC cell lines partly annotated with mutational-, DNA copy number-, and/or gene expression profiles. Post-treatment gene expression profiling and specific protein expression analyses were performed in two pairs of PARP inhibitor sensitive and resistant cell lines.

FINDINGS

A subset of microsatellite stable (MSS) CRCs had truncating mutations in homologous recombination-related genes, but these were not associated with genomic signatures of HRD. Eight CRC cell lines (9%) were sensitive to PARP inhibition, but sensitivity was not predicted by HRD-related genomic and transcriptomic signatures. In contrast, drug sensitivity in MSS cell lines was strongly associated with TP53 wild-type status (odds ratio 15.7, p = 0.023) and TP53-related expression signatures. Increased downstream TP53 activity was among the primary response mechanisms, and TP53 inhibition antagonized the effect of PARP inhibitors. Wild-type TP53-mediated suppression of RAD51 was identified as a possible mechanism of action for sensitivity to PARP inhibition.

INTERPRETATION

PARP inhibitors are active in a subset of CRC cell lines and preserved TP53 function may increase the likelihood of response.

The DNA damage response pathway as a land of therapeutic opportunities for colorectal cancer

BACKGROUND

Colorectal cancer (CRC) represents a major cause of cancer deaths worldwide. Although significant progress has been made by molecular and immune therapeutic approaches, prognosis of advanced stage disease is still dismal. Alterations in the DNA damage response (DDR) pathways are emerging as novel targets for treatment across different cancer types. However, even though preclinical studies have shown the potential exploitation of DDR alterations in CRC, systematic and comprehensive testing is lagging and clinical development is based on analogies with other solid tumors according to a tissue-agnostic paradigm. Recently, functional evidence from patient-derived xenografts and organoids have suggested that maintenance with PARP inhibitors might represent a therapeutic opportunity in CRC patients previously responsive to platinum-based treatment.

DESIGN AND RESULTS

In this review, we highlight the most promising preclinical data and systematically summarize published clinical trials in which DDR inhibitors have been used for CRC and provide evidence that disappointing results have been mainly due to a lack of clinical and molecular selection.

CONCLUSIONS

Future preclinical and translational research will help in better understanding the role of DDR alterations in CRC and pave the way to novel strategies that might have a transformative impact on treatment by identifying new therapeutic options including tailored use of standard chemotherapy.

Expression of poly-ADP-ribose polymerase (PARP) in endometrial adenocarcinoma: Prognostic potential

BACKGROUND

In the United States endometrial carcinoma is the most common female gynecologic malignancy. An average of more than 60,000 new cases of endometrial carcinomas have been diagnosed yearly over the past 5 years, with a higher incidence occurring in the central Appalachian states of Ohio and West Virginia. In the U.S., the national average of newly diagnosed endometrial carcinomas is 26.8 in every 100,000 women, while in the states of Ohio and West Virginia the average is 30.5 and 31.1 in every 100,000 women, respectively. This notable increase in the incidence of endometrial carcinomas may be due a variety of elevated risk factors including but not limited to: tobacco use, obesity, and genetic predisposition of the predominant demographic. The American Cancer Society estimates that approximately 55,000 new cases of endometrial carcinoma will be diagnosed in 2020 yet, this disease is widely considered understudied and under-represented in mainstream cancer research circles.

METHODS

The aim of this study was to quantitate the co-expression of two DNA repair proteins poly-ADP-ribose polymerase 1 and 2 (Parp-1 and Parp-2) by enzyme- linked immuno-sorbent assay (ELISA) in 60 endometrioid endometrial tumor samples and compare their expression to matched non-malignant endometrial tissue from the same corresponding donors from central Appalachia.

RESULTS

We found that Parp-1 was significantly overexpressed in endometrial carcinoma relative to corresponding normal tissue. This overexpression implicates Parp inhibition therapy as a possible treatment for the disease. Our results also found a protective effect of native Parp-2 expression in non-malignant endometrial tissue with each 1 ng/mL increase in PARP-2 concentration in normal tissue was associated with a 10 % reduction in the hazard of tumor progression (HR = 0.90; p = 0.039) and a 21 % reduction in the hazard of death (HR = 0.79; p = 0.044).

CONCLUSIONS

This study demonstrated the over-expression of the druggable target Parp-1 in endometrial adenocarcinoma and observed a strong negative correlation of native Parp-2 expression and disease progression via the quantification of the Parp proteins using enzyme- linked immuno-sorbent assay (ELISA) assays.