Perspectives on cancer therapy-synthetic lethal precision medicine strategies, molecular mechanisms, therapeutic targets and current technical challenges

In recent years, synthetic lethality has become an important theme in the field of targeted cancer therapy. Synthetic lethality refers to simultaneous defects in two or more genes leading to cell death, whereas defects in any single gene do not lead to cell death. Taking advantage of the genetic vulnerability that exists within cancer cells, it theoretically has no negative impact on healthy cells and has fewer side effects than non-specific chemotherapy. Currently, targeted cancer therapies focus on inhibiting key pathways in cancer. However, it has been found that over-activation of oncogenic-related signaling pathways can also induce cancer cell death, which is a major breakthrough in the new field of targeted therapies. In this review, we summarize the conventional gene targets in synthetic lethality (PARP, ATR, ATM, WEE1, PRMT) and provide an in-depth analysis of their latest potential mechanisms. We explore the impact of over-activation of pathways such as PI3K/AKT, MAPK, and WNT on cancer cell survival, and present the technical challenges of current research. Important theoretical foundations and insights are provided for the application of synthetic lethal strategies in cancer therapy, as well as future research directions.

AutoDesigner - Core Design, a De Novo Design Algorithm for Chemical Scaffolds: Application to the Design and Synthesis of Novel Selective Wee1 Inhibitors

The hit identification stage of a drug discovery program generally involves the design of novel chemical scaffolds with desired biological activity against the target(s) of interest. One common approach is scaffold hopping, which is the manual design of novel scaffolds based on known chemical matter. One major limitation of this approach is narrow chemical space exploration, which can lead to difficulties in maintaining or improving biological activity, selectivity, and favorable property space. Another limitation is the lack of preliminary structure-activity relationship (SAR) data around these designs, which could lead to selecting suboptimal scaffolds to advance lead optimization. To address these limitations, we propose AutoDesigner - Core Design (CoreDesign), a de novo scaffold design algorithm. Our approach is a cloud-integrated, de novo design algorithm for systematically exploring and refining chemical scaffolds against biological targets of interest. The algorithm designs, evaluates, and optimizes a vast range, from millions to billions, of molecules in silico, following defined project parameters encompassing structural novelty, physicochemical attributes, potency, and selectivity using active-learning FEP. To validate CoreDesign in a real-world drug discovery setting, we applied it to the design of novel, potent Wee1 inhibitors with improved selectivity over PLK1. Starting from a single known ligand and receptor structure, CoreDesign rapidly explored over 23 billion molecules to identify 1,342 novel chemical series with a mean of 4 compounds per scaffold. To rapidly analyze this large amount of data and prioritize chemical scaffolds for synthesis, we utilize t-Distributed Stochastic Neighbor Embedding (t-SNE) plots of in silico properties. The chemical space projections allowed us to rapidly identify a structurally novel 5-5 fused core meeting all the hit-identification requirements. Several compounds were synthesized and assayed from the scaffold, displaying good potency against Wee1 and excellent PLK1 selectivity. Our results suggest that CoreDesign can significantly speed up the hit-identification process and increase the probability of success of drug discovery campaigns by allowing teams to bring forward high-quality chemical scaffolds derisked by the availability of preliminary SAR.

The power and the promise of synthetic lethality for clinical application in cancer treatment

Synthetic lethality is a phenomenon wherein the simultaneous deficiency of two or more genes results in cell death, while the deficiency of any individual gene does not lead to cell death. In recent years, synthetic lethality has emerged as a significant topic in the field of targeted cancer therapy, with certain drugs based on this concept exhibiting promising outcomes in clinical trials. Nevertheless, the presence of tumor heterogeneity and the intricate DNA repair mechanisms pose challenges to the effective implementation of synthetic lethality. This review aims to explore the concepts, development, and ethical quandaries surrounding synthetic lethality. Additionally, it will provide an in-depth analysis of the clinical application and underlying mechanism of synthetic lethality.

Smoking induces WEE1 expression to promote docetaxel resistance in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) patients have poor clinical outcomes, with an overall 5-year survival rate of 20%. Smoking is a significant risk factor for EAC. The role of WEE1, a nuclear kinase that negatively regulates the cell cycle in normal conditions, in EAC tumorigenesis and drug resistance is not fully understood. Immunohistochemistry staining shows significant WEE1 overexpression in human EAC tissues. Nicotine, nicotine-derived nitrosamine ketone, or 2% cigarette smoke extract treatment induces WEE1 protein expression in EAC, detected by western blot and immunofluorescence staining. qRT-PCR and reporter assay indicates that smoking induces WEE1 expression through miR-195-5p downregulation in EAC. ATP-Glo cell viability and clonogenic assay confirmed that WEE1 inhibition sensitizes EAC cells to docetaxel treatment in vitro. A TE-10 smoking machine with EAC patient-derived xenograft mouse model demonstrated that smoking induces WEE1 protein expression and resistance to docetaxel in vivo. MK-1775 and docetaxel combined treatment improves EAC patient-derived xenograft mouse survival in vivo. Our findings demonstrate, for the first time, that smoking-induced WEE1 overexpression through miRNA dysregulation in EAC plays an essential role in EAC drug resistance. WEE1 inhibition is a promising therapeutic method to overcome drug resistance and target treatment refractory cancer cells.

Understanding DNA Damage Response and DNA Repair in Multiple Myeloma

Multiple myeloma (MM) is a plasma cell malignancy characterized by several genetic abnormalities, including chromosomal translocations, genomic deletions and gains, and point mutations. DNA damage response (DDR) and DNA repair mechanisms are altered in MM to allow for tumor development, progression, and resistance to therapies. Damaged DNA rarely induces an apoptotic response, given the presence of ataxia-telangiectasia mutated (ATM) loss-of-function or mutations, as well as deletions, mutations, or downregulation of tumor protein p53 (TP53) and tumor protein p73 (TP73). Moreover, DNA repair mechanisms are either hyperactive or defective to allow for rapid correction of the damage or permissive survival. Medications used to treat patients with MM can induce DNA damage, by either direct effects (mono-adducts induced by melphalan), or as a result of reactive oxygen species (ROS) production by proteasome inhibitors such as bortezomib. In this review, we will describe the mechanisms of DDR and DNA repair in normal tissues, the contribution of these pathways to MM disease progression and other phenotypes, and the potential therapeutic opportunities for patients with MM.

Genomic and Epigenetic Changes Drive Aberrant Skeletal Muscle Differentiation in Rhabdomyosarcoma

Rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children and adolescents, represents an aberrant form of skeletal muscle differentiation. Both skeletal muscle development, as well as regeneration of adult skeletal muscle are governed by members of the myogenic family of regulatory transcription factors (MRFs), which are deployed in a highly controlled, multi-step, bidirectional process. Many aspects of this complex process are deregulated in RMS and contribute to tumorigenesis. Interconnected loops of super-enhancers, called core regulatory circuitries (CRCs), define aberrant muscle differentiation in RMS cells. The transcriptional regulation of MRF expression/activity takes a central role in the CRCs active in skeletal muscle and RMS. In PAX3::FOXO1 fusion-positive (PF+) RMS, CRCs maintain expression of the disease-driving fusion oncogene. Recent single-cell studies have revealed hierarchically organized subsets of cells within the RMS cell pool, which recapitulate developmental myogenesis and appear to drive malignancy. There is a large interest in exploiting the causes of aberrant muscle development in RMS to allow for terminal differentiation as a therapeutic strategy, for example, by interrupting MEK/ERK signaling or by interfering with the epigenetic machinery controlling CRCs. In this review, we provide an overview of the genetic and epigenetic framework of abnormal muscle differentiation in RMS, as it provides insights into fundamental mechanisms of RMS malignancy, its remarkable phenotypic diversity and, ultimately, opportunities for therapeutic intervention.

Upfront Biology-Guided Therapy in Diffuse Intrinsic Pontine Glioma: Therapeutic, Molecular, and Biomarker Outcomes from PNOC003

PURPOSE

PNOC003 is a multicenter precision medicine trial for children and young adults with newly diagnosed diffuse intrinsic pontine glioma (DIPG).

PATIENTS AND METHODS

Patients (3-25 years) were enrolled on the basis of imaging consistent with DIPG. Biopsy tissue was collected for whole-exome and mRNA sequencing. After radiotherapy (RT), patients were assigned up to four FDA-approved drugs based on molecular tumor board recommendations. H3K27M-mutant circulating tumor DNA (ctDNA) was longitudinally measured. Tumor tissue and matched primary cell lines were characterized using whole-genome sequencing and DNA methylation profiling. When applicable, results were verified in an independent cohort from the Children's Brain Tumor Network (CBTN).

RESULTS

Of 38 patients enrolled, 28 patients (median 6 years, 10 females) were reviewed by the molecular tumor board. Of those, 19 followed treatment recommendations. Median overall survival (OS) was 13.1 months [95% confidence interval (CI), 11.2-18.4] with no difference between patients who followed recommendations and those who did not. H3K27M-mutant ctDNA was detected at baseline in 60% of cases tested and associated with response to RT and survival. Eleven cell lines were established, showing 100% fidelity of key somatic driver gene alterations in the primary tumor. In H3K27-altered DIPGs, TP53 mutations were associated with worse OS (TP53mut 11.1 mo; 95% CI, 8.7-14; TP53wt 13.3 mo; 95% CI, 11.8-NA; P = 3.4e-2), genome instability (P = 3.1e-3), and RT resistance (P = 6.4e-4). The CBTN cohort confirmed an association between TP53 mutation status, genome instability, and clinical outcome.

CONCLUSIONS

Upfront treatment-naïve biopsy provides insight into clinically relevant molecular alterations and prognostic biomarkers for H3K27-altered DIPGs.

Verbascoside enhances radiosensitivity of hepatocellular carcinoma cells through regulating miR-101-3p/Wee1 axis

Verbascoside is a kind of phenylpropanoid glycoside derived from multiple medicinal plants, exerting anti-tumor effects in diverse human malignancies. However, the function of Verbascoside on the radiosensitivity of hepatocellular carcinoma (HCC) cells remains unknown. Human Huh7 and HepG2 cell lines were treated with Verbascosideis, and cell viability was detected with cell counting kit-8 (CCK-8) assay. Quantitative real-time polymerase chain reaction (qRT-PCR) was applied to detect miR-101-3p expression, and Western blot was used to quantify the expression of WEE1 G2 checkpoint kinase (WEE1). Then, CCK-8 and flow cytometry assays were used to detect the proliferation and apoptosis of HCC cells after Verbascoside and X-ray combined treatment, and the expressions of WEE1 and apoptosis-related proteins Bax and Bcl-2 were detected by Western blot. Verbascoside could improve the radiosensitivity of HCC cells in a dose-dependent manner. Verbascoside increased the expression of miR-101-3p but reduced WEE1 expression in HCC cells. Additionally, WEE1 was identified as a target of miR-101-3p. MiR-101-3p inhibition or WEE1 overexpression could reverse the effect of Verbascoside on the viability and apoptosis of HCC cells. Verbascoside increases the radiosensitivity of hepatocellular carcinoma cells via modulating miR-101-3p/WEE1 axis.

Wee1 kinase inhibitor adavosertib with radiation in newly diagnosed diffuse intrinsic pontine glioma: A Children's Oncology Group phase I consortium study

Background

Children with diffuse intrinsic pontine gliomas (DIPG) have a dismal prognosis. Adavosertib (AZD1775) is an orally available, blood-brain barrier penetrant, Wee1 kinase inhibitor. Preclinical efficacy against DIPG is heightened by radiation induced replication stress.

Methods

Using a rolling six design, 7 adavosertib dose levels (DLs) (50 mg/m2 alternating weeks, 50 mg/m2 alternating with weeks of every other day, 50 mg/m2, then 95, 130, 160, 200 mg/m2) were assessed. Adavosertib was only given on days of cranial radiation therapy (CRT).The duration of CRT (54 Gy over 30 fractions; 6 weeks) constituted the dose limiting toxicity (DLT) period. Endpoints included tolerability, pharmacokinetics, overall survival (OS) and peripheral blood γH2AX levels as a marker of DNA damage.

Results

A total of 46 eligible patients with newly diagnosed DIPG [median (range) age 6 (3-21) years; 52% female] were enrolled. The recommend phase 2 dose (RP2D) of adavosertib was 200 mg/m2/d during days of CRT. Dose limiting toxicity included ALT elevation (n = 1, DL4) and neutropenia (n = 1, DL7). The mean Tmax, T1/2 and Clp on Day 1 were 2 h, 4.4 h, and 45.2 L/hr/m2, respectively. Modest accumulation of adavosertib was observed comparing day 5 versus day 1 AUC0-8h (accumulation ratio = 1.6). OS was 11.1 months (95% CI: 9.4, 12.5) and did not differ from historical control.

Conclusion

Adavosertib in combination with CRT is well tolerated in children with newly diagnosed DIPG, however, compared to historical controls, did not improve OS. These results can inform future trial design in children with high-risk cancer.

Long noncoding RNA NORAD acts as a ceRNA mediates gemcitabine resistance in bladder cancer by sponging miR-155-5p to regulate WEE1 expression

BACKGROUND

Increasing evidences have proved that long noncoding RNAs (lncRNAs) regulate the occurrence of bladder cancer (BC) and participate in various pathophysiology processes. However, little is unknown about the role of lncRNAs in drug resistance of BC cells. In this study, we explored the role of non-coding RNA activated by DNA damage (NORAD) in the gemcitabine (GEM) resistant of BC cells and explored its potential mechanism.

METHODS

Real-time quantitative PCR (RT-qPCR) was used to detect the expression of NORAD and miR-155-5p of BC cells. Cell counting kit-8 (CCK-8) and Western blot were used to detect cell inhibition rate and the expression of WEE1 G2 checkpoint kinase (WEE1), P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP1). Flow cytometry detected cell cycle and apoptosis. Dual luciferase reporter gene assay and RNA immunoprecipitation (RIP) assay were used to confirm the targeting relationship between miR-155-5p, NORAD and WEE1. The xenograft model was used to observe the function of NORAD in vivo. immunohistochemistry (IHC) assay was used to detect the expression of WEE1, caspase-3 and Ki67 in tumor tissues.

RESULTS

NORAD highly expressed in GEM-resistant BC cell lines. Knockdown of NORAD significantly inhibited the proliferation of T24/GEM cells, the expression of drug-resistant proteins P-gp and MRP1, inhibit the G0/G1 phase of cells, and induce cell apoptosis. Knockdown of NORAD reversed the promotion effect of miR-155-5p on WEE1 expression and promoted the sensitivity of T24/GEM cells to GEM. In vivo, knockdown of NORAD inhibited the tumor growth, and enhanced the GEM-sensitivity in mice.

CONCLUSION

These data highlight the potential of NORAD acts as a therapeutic target for BC GEM resistance. It revealed the vital roles of NORAD/miR-155-5p/WEE1 axis in GEM resistant BC cells, providing a novel therapeutic strategy for BC.

Recent Advances of WEE1 Inhibitors and Statins in Cancers With p53 Mutations

p53 is among the most frequently mutated tumor suppressor genes given its prevalence in >50% of all human cancers. One critical tumor suppression function of p53 is to regulate transcription of downstream genes and maintain genomic stability by inducing the G1/S checkpoint in response to DNA damage. Tumor cells lacking functional p53 are defective in the G1/S checkpoint and become highly dependent on the G2/M checkpoint to maintain genomic stability and are consequently vulnerable to Wee1 inhibitors, which override the cell cycle G2/M checkpoint and induce cell death through mitotic catastrophe. In addition to the lost tumor suppression function, many mutated p53 (Mutp53) proteins acquire gain-of-function (GOF) activities as oncogenes to promote cancer progression, which manifest through aberrant expression of p53. In cancer cells with GOF Mutp53, statins can induce CHIP-mediated degradation of Mutp53 within the mevalonate pathway by blocking the interaction between mutp53 and DNAJA1. Therefore, targeting critical downstream pathways of Mutp53 provides an alternative strategy for treating cancers expressing Mutp53. In this review, we summarize recent advances with Wee1 inhibitors, statins, and mevalonate pathway inhibitors in cancers with p53 mutations.

Systematic identification of novel cancer genes through analysis of deep shRNA perturbation screens

Systematic perturbation screens provide comprehensive resources for the elucidation of cancer driver genes. The perturbation of many genes in relatively few cell lines in such functional screens necessitates the development of specialized computational tools with sufficient statistical power. Here we developed APSiC (Analysis of Perturbation Screens for identifying novel Cancer genes) to identify genetic drivers and effectors in perturbation screens even with few samples. Applying APSiC to the shRNA screen Project DRIVE, APSiC identified well-known and novel putative mutational and amplified cancer genes across all cancer types and in specific cancer types. Additionally, APSiC discovered tumor-promoting and tumor-suppressive effectors, respectively, for individual cancer types, including genes involved in cell cycle control, Wnt/β-catenin and hippo signalling pathways. We functionally demonstrated that LRRC4B, a putative novel tumor-suppressive effector, suppresses proliferation by delaying cell cycle and modulates apoptosis in breast cancer. We demonstrate APSiC is a robust statistical framework for discovery of novel cancer genes through analysis of large-scale perturbation screens. The analysis of DRIVE using APSiC is provided as a web portal and represents a valuable resource for the discovery of novel cancer genes.

Phase 1 trial of adavosertib (AZD1775) in combination with concurrent radiation and cisplatin for intermediate-risk and high-risk head and neck squamous cell carcinoma

BACKGROUND

Adavosertib (AZD1775) is an inhibitor of the Wee1 kinase. The authors conducted a phase 1b trial to evaluate the safety of adavosertib in combination with definitive chemoradiotherapy for patients with newly diagnosed, intermediate-risk/high-risk, locally advanced head and neck squamous cell carcinoma (HNSCC).

METHODS

Twelve patients with intermediate-risk/high-risk HNSCC were enrolled, including those with p16-negative tumors of the oropharynx, p16-positive tumors of the oropharynx with ≥10 tobacco pack-years, and tumors of the larynx/hypopharynx regardless of p16 status. All patients were treated with an 8-week course of concurrent intensity-modulated radiotherapy at 70 grays (Gy) (2 Gy daily in weeks 1-7), cisplatin 30 mg/m² weekly (in weeks 1-7), and adavosertib (twice daily on Monday, Tuesday, and Wednesday of weeks 1, 2, 4, 5, 7, and 8). The primary objective was to determine the maximum tolerated dose and the recommended phase 2 dose of adavosertib given concurrently with radiation and cisplatin. Secondary objectives were to determine the 12-week objective response rate and progression-free and overall survival.

RESULTS

Three patients (25%) experienced a dose-limiting toxicity, including febrile neutropenia (n = 2) and grade 4 thromboembolism (n = 1). Two dose-limiting toxicities occurred with adavosertib at 150 mg. The median follow-up was 14.7 months. The 12-week posttreatment objective response rate determined by positron emission tomography/computed tomography was 100%. The 1-year progression-free and overall survival rates were both 90%. The maximum tolerated dose of adavosertib was 100 mg.

CONCLUSIONS

Adavosertib 100 mg (twice daily on Monday, Tuesday, and Wednesday of weeks 1, 2, 4, 5, 7, and 8), in combination with 70 Gy of intensity-modulated radiotherapy and cisplatin 30 mg/m² , is the recommended phase 2 dose for patients with HNSCC.

Efficacy of adavosertib therapy against anaplastic thyroid cancer

Wee1 is a kinase that regulates the G2/M progression by the inhibition of CDK1, which is critical for ensuring DNA damage repair before initiation of mitotic entry. Targeting Wee1 may be a potential strategy in the treatment of anaplastic thyroid cancer, a rare but lethal disease. The therapeutic effects of adavosertib, a Wee1 inhibitor for anaplastic thyroid cancer was evaluated in this study. Adavosertib inhibited cell growth in three anaplastic thyroid cancer cell lines in a dose-dependent manner. Cell cycle analysis revealed cells were accumulated in the G2/M phase. Adavosertib induced caspase-3 activity and led to apoptosis. Adavosertib monotherapy showed significant retardation of the growth of two anaplastic thyroid cancer tumor models. The combination of adavosertib with dabrafenib and trametinib revealed strong synergism in vitro and demonstrated robust suppression of tumor growth in vivo in anaplastic thyroid cancer xenograft models with BRAFV600E mutation. The combination of adavosertib with either sorafenib or lenvatinib also demonstrated synergism in vitro and had strong inhibition of tumor growth in vivo in an anaplastic thyroid cancer xenograft model. No appreciable toxicity appeared in mice treated with either a single agent or combination treatment. Our findings suggest adavosertib holds the promise for the treatment of patients with anaplastic thyroid cancer.

The lncRNA XIST/miR-125b-2-3p axis modulates cell proliferation and chemotherapeutic sensitivity via targeting Wee1 in colorectal cancer

Background

Numerous reports on microRNAs have illustrated their role in tumor growth and metastasis. Recently, a new prognostic factor, miR‐125b‐2‐3p, has been identified for predicting chemotherapeutic sensitivity in advanced colorectal cancer (CRC). However, the specific mechanisms and biological functions of miR‐125b‐2‐3p in advanced CRC under chemotherapy have yet to be elucidated.

Methods

MiR‐125b‐2‐3p expression was detected by real‐time PCR (RT‐PCR) in CRC tissues. The effects of miR‐125b‐2‐3p on the growth, metastasis, and drug sensitivity of CRC cells were tested in vitro and in vivo. Based on multiple databases, the upstream competitive endogenous RNAs (ceRNAs) and the downstream genes for miR‐125b‐2‐3p were predicted by bioinformatic analysis, followed by the experiments including luciferase reporter assays, western blot assays, and so on.

Results

MiR‐125b‐2‐3p was significantly lowly expressed in the tissues and cell lines of CRC. Higher expression of miR‐125b‐2‐3p was associated with relatively lower proliferation rates and fewer metastases. Moreover, overexpressed miR‐125b‐2‐3p remarkably improved chemotherapeutic sensitivity of CRC in vivo and in vitro. Mechanistically, miR‐125b‐2‐3p was absorbed by long noncoding RNA (lncRNA) XIST regulating WEE1 G2 checkpoint kinase (WEE1) expression. The upregulation of miR‐125b‐2‐3p inhibited the proliferation and epithelial‐mesenchymal transition (EMT) of CRC induced by lncRNA XIST.

Conclusions

Lower miR‐125b‐2‐3p expression resulted in lower sensitivity of CRC to chemotherapy and was correlated with poorer survival of CRC patients. LncRNA XIST promoted CRC metastasis acting as a ceRNA for miR‐125b‐2‐3p to mediate WEE1 expression. LncRNA XIST‐miR‐125b‐2‐3p‐WEE1 axis not only regulated CRC growth and metastasis but also contributed to chemotherapeutic resistance to CRC.

Long noncoding RNA LINC01410 promotes the tumorigenesis of neuroblastoma cells by sponging microRNA-506-3p and modulating WEE1

OBJECTIVE

Neuroblastoma (NBL) is an extra-cranial solid tumor in children. This study was attempted to investigate the regulatory mechanism of long noncoding RNA LINC01410 (LINC01410) on NBL.

METHODS

The expression of LINC01410, miR-506-3p, and WEE1 in NBL was evaluated by quantitative real time polymerase chain reaction. The proliferation and colony formation ability of NBL cells were analyzed by MTT and colony formation assay. Flow cytometry assay was executed to measure the apoptosis and cell cycle. Dual-luciferase reporter assay was used to detect the targeted relationships among LINC01410, miR-506-3p, and WEE1. Additionally, the role of LINC01410 on NBL in vivo was evaluated according to a tumor xenograft model.

RESULTS

The expression of LINC01410 and WEE1 was enhanced and miR-506-3p was inhibited in NBL. LINC01410 knockdown attenuated the cell proliferation, colony formation ability, and inhibited tumor growth. Moreover, LINC01410 silencing facilitated the apoptosis and arrested the cell cycle. LINC01410 interacted with miR-506-3p to elevate the WEE1 expression in NBL. Additionally, miR-506-3p inhibition or WEE1 overexpression weakened the reduction effects of sh-LINC01410 on cell proliferation, colony formation ability, apoptosis, and cell cycle.

CONCLUSIONS

Knockdown of LINC01410 inhibited the development of NBL by miR-506-3p/WEE1 axis in vitro, which could serve as a potential therapeutic target for NBL therapy.

Structure-activity relationships of Wee1 inhibitors: A review

Wee1 kinase plays an important role in regulating G2/M checkpoint and S phase, and the inhibition of it will lead to mitotic catastrophe in cancer cells with p53 mutation or deletion. Therefore, the mechanism of Wee1 kinase in cancer treatment and the development of its inhibitors have become a research hotspot. However, although a variety of Wee1 inhibitors with different scaffolds and considerable activity have been successfully identified, so far no one has systematically summarized the structure-activity relationships (SARs) of Wee1 inhibitors. Previous reviews mainly focused on its mechanism and clinical application. To facilitate the rational design and development of Wee1 inhibitors in the future, this paper systematically summarizes its structural types, SARs and binding modes according to the Wee1 inhibitors reported in scientific journals, and also summarizes the regulatory effect of Wee1 kinase on cell cycle and the progress of its inhibitors in clinical application.

A serine/threonine protein PIM kinase as a biomarker of cancer and a target for anti-tumor therapy

The PIM Kinases belong to the family of a proto-oncogene that essentially phosphorylates the serine/threonine residues of the target proteins. They are primarily categorized into three types PIM-1, PIM-2, PIM-3 which plays an indispensable regulatory role in signal transduction cascades, by promoting cell survival, proliferation, and drug resistance. These kinases are overexpressed in several solid as well as hematopoietic tumors which supports in vitro and in vivo malignant cell growth along with survival by regulating cell cycle and inhibiting apoptosis. They lack regulatory domain which makes them constitutively active once transcribed. PIM kinases usually appear to be important downstream effectors of oncoproteins which overexpresses and helps in mediating drug resistance to available agents, such as rapamycin. Structural studies of PIM kinases revealed that they have unique hinge regions where two Proline resides and makes ATP binding unique, by offering a target for an increasing number of potent PIM kinase inhibitors. Preclinical studies of those inhibitory compounds in various cancers indicate that these novel agents show promising activity and some of them currently being under examination. In this review, we have outlined PIM kinases molecular mechanism and signaling pathways along with matriculation in various cancer and list of inhibitors often used.

Targeting MYC-driven replication stress in medulloblastoma with AZD1775 and gemcitabine

PURPOSE

MYC-driven medulloblastomas are highly aggressive childhood tumors with dismal outcomes and a lack of new treatment paradigms. We identified that targeting replication stress through WEE1 inhibition to suppress the S-phase replication checkpoint, combined with the attenuation of nucleotide synthesis with gemcitabine, is an effective strategy to induce apoptosis in MYC-driven medulloblastoma that could be rapidly translated into early phase clinical trials in children. Attenuation of replication stress is a key component of MYC-driven oncogenesis. Previous studies revealed a vulnerability in MYC medulloblastoma through WEE1 inhibition. Here, we focused on elucidating combinations of agents to synergize with WEE1 inhibition and drive replication stress toward cell death.

METHODS

We first analyzed WEE1 expression in patient tissues by immunohistochemistry. Next, we used high-throughput drug screens to identify agents that would synergize with WEE1 inhibition. Synergy was confirmed by in vitro live cell imaging, ex vivo slice culture models, and in vivo studies using orthotopic and flank xenograft models.

RESULTS

WEE1 expression was significantly higher in Group 3 and 4 medulloblastoma patients. The WEE1 inhibitor AZD1775 synergized with inhibitors of nucleotide synthesis, including gemcitabine. AZD1775 with gemcitabine suppressed proliferation and induced apoptosis. Ex vivo modeling demonstrated efficacy in Group 3 medulloblastoma patients, and in vivo modeling confirmed that combining AZD1775 and gemcitabine effectively suppressed tumor growth.

CONCLUSION

Our results identified a potent new synergistic treatment combination for MYC-driven medulloblastoma that warrants exploration in early phase clinical trials.

Targeting the WEE1 kinase strengthens the antitumor activity of imatinib via promoting KIT autophagic degradation in gastrointestinal stromal tumors

BACKGROUND

Activating mutation of KIT or PDGFRA is the primary molecular mechanism for gastrointestinal stromal tumors (GISTs). Although imatinib has a revolutionary effect on GIST therapeutics, the benefits are not durable. Increasing reports have demonstrated that cell cycle checkpoint plays critical roles in GIST. Here, we explore the role of WEE1 kinase in GIST progression.

METHODS

Oncomine public database, western blotting, and immunohistochemistry were used to analyze WEE1 expression in GISTs. Using MTT assays, colony formation analysis, and flow cytometry, we examined the role of WEE1 in GIST cells and the antitumor activity of the inhibitor MK1775 alone, or in combination with imatinib. Cycloheximide chase assay and pharmacological inhibition of autophagy and proteasome pathway were performed to analyze KIT expression. Additionally, autophagic markers Beclin1 and LC3B were detected by western blotting.

RESULTS

Upregulated WEE1 expression was observed in GIST tissues and correlated with tumor size, mitotic count, and risk grade. Inhibition of WEE1 significantly suppressed GIST cell proliferation, induced apoptosis and cell cycle arrest. Imatinib and MK1775 co-treatment markedly enhanced the antitumor activity. Targeting WEE1 decreased the expression of KIT expression. Moreover, WEE1 stabilized KIT protein and KIT reduction observed upon WEE1 inhibition could be reversed by pharmacological inhibition of autophagy, but not proteasome pathway. WEE1 inhibition also increased Beclin1 expression and LC3B II/I ratio in GIST cells.

CONCLUSIONS

Our data suggest that WEE1 plays a pivotal role in GIST proliferation. WEE1 inhibition could promote KIT autophagic degradation and, therefore, targeting WEE1 might represent a novel strategy for GIST therapies.

Altering DNA Repair to Improve Radiation Therapy: Specific and Multiple Pathway Targeting

Radiation therapy (RT) is widely used in cancer care strategies. Its effectiveness relies mainly on its ability to cause lethal damage to the DNA of cancer cells. However, some cancers have shown to be particularly radioresistant partly because of efficient and redundant DNA repair capacities. Therefore, RT efficacy might be enhanced by using drugs that can disrupt cancer cells' DNA repair machinery. Here we review the recent advances in the development of novel inhibitors of DNA repair pathways in combination with RT. A large number of these compounds are the subject of preclinical/clinical studies and target key enzymes involved in one or more DNA repair pathways. A totally different strategy consists of mimicking DNA double-strand breaks via small interfering DNA (siDNA) to bait the whole DNA repair machinery, leading to its global inhibition.

p21 limits S phase DNA damage caused by the Wee1 inhibitor MK1775

The Wee1 inhibitor MK1775 (AZD1775) is currently being tested in clinical trials for cancer treatment. Here, we show that the p53 target and CDK inhibitor p21 protects against MK1775-induced DNA damage during S-phase. Cancer and normal cells deficient for p21 (HCT116 p21^-/-, RPE p21^-/-, and U2OS transfected with p21 siRNA) showed higher induction of the DNA damage marker γH2AX in S-phase in response to MK1775 compared to the respective parental cells. Furthermore, upon MK1775 treatment the levels of phospho-DNA PKcs S2056 and phospho-RPA S4/S8 were higher in the p21 deficient cells, consistent with increased DNA breakage. Cell cycle analysis revealed that these effects were due to an S-phase function of p21, but MK1775-induced S-phase CDK activity was not altered as measured by CDK-dependent phosphorylations. In the p21 deficient cancer cells MK1775-induced cell death was also increased. Moreover, p21 deficiency sensitized to combined treatment of MK1775 and the CHK1-inhibitor AZD6772, and to the combination of MK1775 with ionizing radiation. These results show that p21 protects cancer cells against Wee1 inhibition and suggest that S-phase functions of p21 contribute to mediate such protection. As p21 can be epigenetically downregulated in human cancer, we propose that p21 levels may be considered during future applications of Wee1 inhibitors.

A pilot precision medicine trial for children with diffuse intrinsic pontine glioma-PNOC003: A report from the Pacific Pediatric Neuro-Oncology Consortium

This clinical trial evaluated whether whole exome sequencing (WES) and RNA sequencing (RNAseq) of paired normal and tumor tissues could be incorporated into a personalized treatment plan for newly diagnosed patients (<25 years of age) with diffuse intrinsic pontine glioma (DIPG). Additionally, whole genome sequencing (WGS) was compared to WES to determine if WGS would further inform treatment decisions, and whether circulating tumor DNA (ctDNA) could detect the H3K27M mutation to allow assessment of therapy response. Patients were selected across three Pacific Pediatric Neuro-Oncology Consortium member institutions between September 2014 and January 2016. WES and RNAseq were performed at diagnosis and recurrence when possible in a CLIA-certified laboratory. Patient-derived cell line development was attempted for each subject. Collection of blood for ctDNA was done prior to treatment and with each MRI. A specialized tumor board generated a treatment recommendation including up to four FDA-approved agents based upon the genomic alterations detected. A treatment plan was successfully issued within 21 business days from tissue collection for all 15 subjects, with 14 of the 15 subjects fulfilling the feasibility criteria. WGS results did not significantly deviate from WES-based therapy recommendations; however, WGS data provided further insight into tumor evolution and fidelity of patient-derived cell models. Detection of the H3F3A or HIST1H3B K27M (H3K27M) mutation using ctDNA was successful in 92% of H3K27M mutant cases. A personalized treatment recommendation for DIPG can be rendered within a multicenter setting using comprehensive next-generation sequencing technology in a clinically relevant timeframe.

Association between MicroRNA-373 and Long Noncoding RNA NORAD in Hepatitis C Virus-Infected Hepatocytes Impairs Wee1 Expression for Growth Promotion

Chronic hepatitis C virus (HCV) infection may lead to end-stage liver disease, including hepatocellular carcinoma (HCC). We have shown previously that microRNA-373 (miR-373) is upregulated in HCV-infected human liver biopsy specimens. To gain insight into the role of miR-373 in HCV-mediated pathogenesis, we investigated its interacting partner for hepatocyte growth regulation. Transcriptome sequencing (RNA-seq) data revealed that Wee1 is associated with miR-373 and is a direct target. Interestingly, higher expression of Wee1 was noted in HCV-infected hepatocytes than in uninfected hepatocytes, suggesting that other factors may block miR-373-mediated Wee1 inhibition. We subsequently found an association between the long noncoding RNA NORAD (LINC00657) and miR-373, and we demonstrated that NORAD binds to miR-373 and Wee1 independently. However, the high level of Wee1 expression in HCV-infected hepatocytes suggested that miR-373 forms a complex with NORAD. Depletion of miR-373 or the inhibitor Wee1 reduces the growth of Huh7.5 cells harboring the HCV genome as well as reducing Wee1 expression. Taken together, our data demonstrate a novel mechanism of hepatocyte growth promotion during HCV infection involving a miR-373-NORAD-Wee1 axis, which may be a target for future therapy against HCV-associated HCC.IMPORTANCE The mechanism of HCV-mediated liver pathogenesis is poorly understood. In this study, we observed that HCV infection upregulates miR-373 and Wee1, a pivotal player in the G₂ checkpoint in the cell cycle, although Wee1 is a direct target for miR-373. Subsequent investigation demonstrated that miR-373 forms a complex with the long noncoding RNA NORAD, resulting in the release of their common target, Wee1, in HCV-infected cells, which, in turn, favors uncontrolled cell growth. Our study suggested a previously unknown mechanism for hepatocyte growth promotion following HCV infection, and this pathway can be targeted for future therapy against HCV-mediated liver pathogenesis.

Phosphorylation of CDC25C by AMP-activated protein kinase mediates a metabolic checkpoint during cell-cycle G2/M-phase transition

From unicellular to multicellular organisms, cell-cycle progression is tightly coupled to biosynthetic and bioenergetic demands. Accumulating evidence has demonstrated the G₁/S-phase transition as a key checkpoint where cells respond to their metabolic status and commit to replicating the genome. However, the mechanism underlying the coordination of metabolism and the G₂/M-phase transition in mammalian cells remains unclear. Here, we show that the activation of AMP-activated protein kinase (AMPK), a highly conserved cellular energy sensor, significantly delays mitosis entry. The cell-cycle G₂/M-phase transition is controlled by mitotic cyclin-dependent kinase complex (CDC2-cyclin B), which is inactivated by WEE1 family protein kinases and activated by the opposing phosphatase CDC25C. AMPK directly phosphorylates CDC25C on serine 216, a well-conserved inhibitory phosphorylation event, which has been shown to mediate DNA damage–induced G₂-phase arrest. The acute induction of CDC25C or suppression of WEE1 partially restores mitosis entry in the context of AMPK activation. These findings suggest that AMPK-dependent phosphorylation of CDC25C orchestrates a metabolic checkpoint for the cell-cycle G₂/M-phase transition.

Chemotherapy-induced differential cell cycle arrest in B-cell lymphomas affects their sensitivity to Wee1 inhibition

Chemotherapeutic agents, e.g., cytarabine and doxorubicin, cause DNA damage. However, it remains unknown whether such agents differentially regulate cell cycle arrest in distinct types of B-cell lymphomas, and whether this phenotype can be exploited for developing new therapies. We treated various types of B cells, including primary and B lymphoma cells, with cytarabine or doxorubicin, and determined DNA damage responses, cell cycle regulation and sensitivity to a Wee1 inhibitor. We found that cyclin A2/B1 upregulation appears to be an intrinsic programmed response to DNA damage; however, different types of B cells arrest in distinct phases of the cell cycle. The Wee1 inhibitor significantly enhanced the apoptosis of G2 phase-arrested B-cell lymphomas by inducing premature entry into mitosis and mitotic catastrophe, whereas it did not affect G1/S-phase-arrested lymphomas. Cytarabine-induced G1-arrest can be converted to G2-arrest by doxorubicin treatment in certain B-cell lymphomas, which correlates with newly acquired sensitivity to the Wee1 inhibitor. Consequently, the Wee1 inhibitor together with cytarabine or doxorubicin inhibited tumor growth in vitro and in vivo more effectively, providing a potential new therapy for treating B-cell lymphomas. We propose that the differential cell cycle arrest can be exploited to enhance the chemosensitivity of B-cell lymphomas.

Targeting DNA damage in SCLC

SCLC accounts for 15% of lung cancer worldwide. Characterised by early dissemination and rapid development of chemo-resistant disease, less than 5% of patients survive 5 years. Despite 3 decades of clinical trials there has been no change to the standard platinum and etoposide regimen for first line treatment developed in the 1970's. The exceptionally high number of genomic aberrations observed in SCLC combined with the characteristic rapid cellular proliferation results in accumulation of DNA damage and genomic instability. To flourish in this precarious genomic context, SCLC cells are reliant on functional DNA damage repair pathways and cell cycle checkpoints. Current cytotoxic drugs and radiotherapy treatments for SCLC have long been known to act by induction of DNA damage and the response of cancer cells to such damage determines treatment efficacy. Recent years have witnessed improved understanding of strategies to exploit DNA damage and repair mechanisms in order to increase treatment efficacy. This review will summarise the rationale to target DNA damage response in SCLC, the progress made in evaluating novel DDR inhibitors and highlight various ongoing challenges for their clinical development in this disease.

DNA damage response as a therapeutic target in gynecological cancers

PURPOSE OF REVIEW

The proven activity of poly ADP ribose polymerase (PARP) inhibitors in BRCA-mutated homologous recombination deficient (HRD) ovarian cancer has led to the availability to patients with ovarian cancer of the first targeted therapy with an associated predictive biomarker. Our focus has recently turned towards expanding the clinical utility of PARP inhibitors beyond BRCA mutated ovarian cancer, and to a search for novel targets within DNA damage response (DDR).

RECENT FINDINGS

Early trials in unselected patients with ovarian cancer showed responses to PARP inhibition in BRCA-wildtype ovarian cancer, and recent genomic studies have demonstrated that germline or somatic aberrations in other homologous recombination genes are present in a significant proportion of ovarian cancers. In addition, PARP inhibition may be of value in molecularly defined subsets of endometrial or cervical cancers. Novel DDR inhibitors such as ATR, ATM, WEE1 or DNA-PK inhibitors are also being tested in patients. Finally, combinatorial strategies of DDR inhibitors with antiangiogenic agents, phosphoinositide 3-kinase inhibitors or immunotherapies may further increase therapeutic efficacy.

SUMMARY

In the future, patients with gynaecological malignancies may be rationally selected for PARP inhibition on the basis of comprehensive evaluation of homologous recombination genomic alterations, or HRD assays. Furthermore, novel DDR inhibitors have the potential to expand the repertoire of therapeutic options available to these patients.

Combined inhibition of Wee1 and Chk1 gives synergistic DNA damage in S-phase due to distinct regulation of CDK activity and CDC45 loading

Recent studies have shown synergistic cytotoxic effects of simultaneous Chk1- and Wee1-inhibition. However, the mechanisms behind this synergy are not known. Here, we present a flow cytometry-based screen for compounds that cause increased DNA damage in S-phase when combined with the Wee1-inhibitor MK1775. Strikingly, the Chk1-inhibitors AZD7762 and LY2603618 were among the top candidate hits of 1664 tested compounds, suggesting that the synergistic cytotoxic effects are due to increased S-phase DNA damage. Combined Wee1- and Chk1-inhibition caused a strong synergy in induction of S-phase DNA damage and reduction of clonogenic survival. To address the underlying mechanisms, we developed a novel assay measuring CDK-dependent phosphorylations in single S-phase cells. Surprisingly, while Wee1-inhibition alone induced less DNA damage compared to Chk1-inhibition, Wee1-inhibition caused a bigger increase in S-phase CDK-activity. However, the loading of replication initiation factor CDC45 was more increased after Chk1- than Wee1-inhibition and further increased by the combined treatment, and thus correlated well with DNA damage. Therefore, when Wee1 alone is inhibited, Chk1 suppresses CDC45 loading and thereby limits the extent of unscheduled replication initiation and subsequent S-phase DNA damage, despite very high CDK-activity. These results can explain why combined treatment with Wee1- and Chk1-inhibitors gives synergistic anti-cancer effects.

Utility of Genomic Analysis In Circulating Tumor DNA from Patients with Carcinoma of Unknown Primary

Carcinoma of unknown primary (CUP) is a rare and difficult-to-treat malignancy, the management of which might be improved by the identification of actionable driver mutations. We interrogated 54 to 70 genes in 442 patients with CUP using targeted clinical-grade, next-generation sequencing of circulating tumor DNA (ctDNA). Overall, 80% of patients exhibited ctDNA alterations; 66% (290/442) ≥1 characterized alteration(s), excluding variants of unknown significance. TP53-associated genes were most commonly altered [37.8% (167/442)], followed by genes involved in the MAPK pathway [31.2% (138/442)], PI3K signaling [18.1% (80/442)], and the cell-cycle machinery [10.4% (46/442)]. Among 290 patients harboring characterized alterations, distinct genomic profiles were observed in 87.9% (255/290) of CUP cases, with 99.7% (289/290) exhibiting potentially targetable alterations. An illustrative patient with dynamic changes in ctDNA content during therapy and a responder given a checkpoint inhibitor-based regimen because of a mismatch repair gene anomaly are presented. Our results demonstrate that ctDNA evaluation is feasible in CUP and that most patients harbor a unique somatic profile with pharmacologically actionable alterations, justifying the inclusion of noninvasive liquid biopsies in next-generation clinical trials. Cancer Res; 77(16); 4238-46. ©2017 AACR.

Targeting DNA Repair in Cancer: Beyond PARP Inhibitors

Germline aberrations in critical DNA-repair and DNA damage-response (DDR) genes cause cancer predisposition, whereas various tumors harbor somatic mutations causing defective DDR/DNA repair. The concept of synthetic lethality can be exploited in such malignancies, as exemplified by approval of poly(ADP-ribose) polymerase inhibitors for treating BRCA1/2-mutated ovarian cancers. Herein, we detail how cellular DDR processes engage various proteins that sense DNA damage, initiate signaling pathways to promote cell-cycle checkpoint activation, trigger apoptosis, and coordinate DNA repair. We focus on novel therapeutic strategies targeting promising DDR targets and discuss challenges of patient selection and the development of rational drug combinations.

SIGNIFICANCE

Various inhibitors of DDR components are in preclinical and clinical development. A thorough understanding of DDR pathway complexities must now be combined with strategies and lessons learned from the successful registration of PARP inhibitors in order to fully exploit the potential of DDR inhibitors and to ensure their long-term clinical success. Cancer Discov; 7(1); 20-37. ©2016 AACR.

Molecular Characterization of Epithelial Ovarian Cancer: Implications for Diagnosis and Treatment

Epithelial ovarian cancer is a highly heterogeneous disease characterized by multiple histological subtypes. Molecular diversity has been shown to occur within specific histological subtypes of epithelial ovarian cancer, between different tumors of an individual patient, as well as within individual tumors. Recent advances in the molecular characterization of epithelial ovarian cancer tumors have provided the basis for a simplified classification scheme in which these cancers are classified as either type I or type II tumors, and these two categories have implications regarding disease pathogenesis and prognosis. Molecular analyses, primarily based on next-generation sequencing, otherwise known as high-throughput sequencing, are allowing for further refinement of ovarian cancer classification, facilitating the elucidation of the site(s) of precursor lesions of high-grade serous ovarian cancer, and providing insight into the processes of clonal selection and evolution that may be associated with development of chemoresistance. Potential therapeutic targets have been identified from recent molecular profiling studies of these tumors, and the effectiveness and safety of a number of specific targeted therapies have been evaluated or are currently being studied for the treatment of women with this disease.

The 'Pushmi-Pullyu' of DNA REPAIR: Clinical Synthetic Lethality

Maintenance of genomic integrity is critical for adaptive survival in the face of endogenous and exogenous environmental stress. The loss of stability and fidelity in the genome caused by cancer and cancer treatment provides therapeutic opportunities to leverage the critical balance between DNA injury and repair. Blocking repair and pushing damaged DNA through the cell cycle using therapeutic inhibitors exemplify the 'pushmi-pullyu' effect of disrupted DNA repair. DNA repair inhibitors (DNARi) can be separated into five biofunctional categories: sensors, mediators, transducers, effectors, and collaborators that recognize DNA damage, propagate injury DNA messages, regulate cell cycle checkpoints, and alter the microenvironment. The result is cancer therapeutics that takes advantage of clinical synthetic lethality, resulting in selective tumor cell kill. Here, we review recent considerations related to DNA repair and new DNARi agents and organize those findings to address future directions and clinical opportunities.

Identification of clinically achievable combination therapies in childhood rhabdomyosarcoma

Purpose

Systemic therapy has improved rhabdomyosarcoma event-free and overall survival; however, approximately 40 % of patients will have progressive or recurrent disease which is difficult to cure and remains a considerable challenge. Minimal progress has been made in improving outcomes for metastatic or relapsed RMS due to a lack of effective therapeutic agents. Targeted therapies are likely to be incorporated into regimens which rely on conventional cytotoxic chemotherapy. A system to evaluate novel combinations of interest is needed.

Methods

In this study, we explored 8 agents, 5 that are routinely used or similar to agents used in the clinical management of RMS and 3 biologically targeted agents with novel mechanisms of action, the Wee1 inhibitor AZD1775, the tyrosine kinase inhibitor cabozantinib, and the proteasome inhibitor bortezomib. All were tested individually at clinically achievable concentrations for activity in 4 RMS cell lines and then for potential synergy in two-drug combinations.

Results

We found single-agent activity in five of the agents (or their active metabolites) that constitute the standard of care in RMS and for AZD1775 with mean IC50 values of 207 ng/ml, well below clinically achievable levels. In addition, the combination of individual cytotoxic chemotherapeutics currently used for RMS demonstrated largely synergistic activity with higher, but clinically achievable concentrations of AZD1775 in our assays.

Conclusions

Prioritization of chemotherapeutics in RMS is possible using an in vitro system that can define novel drug combinations worthy of future investigation. AZD1775 exhibits single-agent activity, as well as synergy with conventional cytotoxic chemotherapy, and is a novel targeted agent that warrants further study in RMS.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-016-3077-8) contains supplementary material, which is available to authorized users.

Expression and clinical significance of Wee1 in colorectal cancer

Wee1 is a nuclear kinase regulating cell cycle progression, and has emerged as a promising therapeutic target in cancer. Expression of Wee1 has been associated with poor outcome in certain tumor types, but the prognostic impact and clinical significance in colorectal cancer is unknown. The expression of Wee1 was examined by immunohistochemistry in primary colorectal carcinomas from a prospectively collected patient cohort, and associations with clinicopathological parameters and outcome were investigated. Cell culture experiments were performed using the cell lines RKO and SW620, and the relationship with the metastasis-promoting protein S100A4 was investigated. Nuclear expression was detected in 229 of the 258 tumors analyzed (89 %). Wee1 staining was associated with low pT stage, but no other significant associations with demographic or histopathological variables were found. Moderate Wee1 staining intensity was a predictor of favorable metastasis-free and overall survival compared to strong intensity and no or weak staining. The fraction of positive cells was not a prognostic factor in the present cohort. Inhibition of Wee1 expression using siRNA or treatment with the Wee1 inhibitor MK-1775 reduced expression of the metastasis-promoting protein S100A4, but no relationship between Wee1 and S100A4 was found in the patient samples. In conclusion, Wee1 is highly expressed in primary colorectal carcinomas, but few relevant associations with clinicopathological parameters or outcome were found. The lack of clinical significance of Wee1 expression could indicate that other tumor types might be better suited for further development of Wee1 inhibitors.

An overview of tyrosine kinase inhibitors for the treatment of epithelial ovarian cancer

INTRODUCTION

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy and the fifth most common cause of cancer-related deaths in women. Initial treatment with surgery and chemotherapy has improved survival significantly. However, the disease progresses or recurs in most patients. Thus, there is an urgent need to develop more effective treatment strategies.

AREAS COVERED

This article provides an overview of tyrosine kinase inhibitors (TKIs) for the treatment of EOC, which is based on English peer-reviewed articles on MEDLINE and related abstracts presented at major conferences. The authors highlight the data from the published clinical trials in EOC patients who were treated with TKIs or TKI-based regimens.

EXPERT OPINION

EOC is responsive to most chemotherapeutic drugs and/or biological agents and represents an ideal disease model for investigating novel anti-cancer agents. Numerous small-molecule TKIs targeting the VEGFR, PARP, PI3K-AKT-mTOR, MAPK, Src, PKC, Wee1 and HER1/2 signaling pathways are currently being tested in clinical trials. Research is needed for devising regimens combining TKIs with other agents in an optimal timing schedule and for identifying potential biomarkers predictive of response and survival.