A phase IA dose-escalation study of PHI-101, a new checkpoint kinase 2 inhibitor, for platinum-resistant recurrent ovarian cancer

Background PHI-101 is an orally available, selective checkpoint kinase 2 (Chk2) inhibitor. PHI-101 has shown anti-tumour activity in ovarian cancer cell lines and impaired DNA repair pathways in preclinical experiments. Furthermore, the in vivo study suggests the synergistic effect of PHI-101 through combination with PARP inhibitors for ovarian cancer treatment. The primary objective of this study is to evaluate the safety and tolerability of PHI-101 in platinum-resistant recurrent ovarian cancer. Methods Chk2 inhibitor for Recurrent EpitheliAl periToneal, fallopIan, or oVarian cancEr (CREATIVE) trial is a prospective, multi-centre, phase IA dose-escalation study. Six cohorts of dose levels are planned, and six to 36 patients are expected to be enrolled in this trial. Major inclusion criteria include ≥ 19 years with histologically confirmed epithelial ovarian cancer, fallopian tube carcinoma, or primary peritoneal cancer. Also, patients who showed disease progression during platinum-based chemotherapy or disease progression within 24 weeks from completion of platinum-based chemotherapy will be included, and prior chemotherapy lines of more than five will be excluded. The primary endpoint of this study is to determine the dose-limiting toxicity (DLT) and maximum tolerated dose (MTD) of PHI-101. Discussion PHI-101 is the first orally available Chk2 inhibitor, expected to show effectiveness in treating recurrent ovarian cancer. Through this CREATIVE trial, DLT and MTD of this new targeted therapy can be confirmed to find the recommended dose for the phase II clinical trial. This study may contribute to developing a new combination regimen for the treatment of ovarian cancer. Trial registration ClinicalTrials.gov Identifier: NCT04678102.

Natural podophyllotoxin analog 4DPG attenuates EMT and colorectal cancer progression via activation of checkpoint kinase 2

Epithelial–mesenchymal transition (EMT) is critical for the metastatic dissemination of cancer cells and contributes to drug resistance. In this study, we observed that epithelial colorectal cancer (CRC) cells transiently exposed to 5-fluorouracil (5-FU) (a chemotherapeutic drug for CRC) as well as 5-FU-resistant cells (5-FU-R) develop EMT characters as evidenced by activation of Vimentin and augmented invasive properties. On the other hand, 4DPG (4′-demethyl-deoxypodophyllotoxin glucoside), a natural podophyllotoxin analog attenuates EMT and invadopodia formation abilities of HCT-116/5-FU-R and SW-620/5-FU-R cells. Treatment with 4DPG restrains Vimentin phosphorylation (Ser38) in 5-FU-R cells, along with downregulation of mesenchymal markers Twist1 and MMP-2 while augmenting the expression of epithelial markers E-cadherin and TIMP-1. Moreover, 4DPG boosts the tumor-suppressor protein, checkpoint kinase 2 (Chk2) via phosphorylation at Thr68 in a dose-dependent manner in 5-FU-R cells. Mechanistically, SiRNA-mediated silencing of Chk2, as well as treatment with Chk2-specific small-molecule inhibitor (PV1019), divulges that 4DPG represses Vimentin activation in a Chk2-dependent manner. Furthermore, immunoprecipitation analysis unveiled that 4DPG prevents complex formation between Vimentin and p53 resulting in the rescue of p53 and its nuclear localization in aggressive 5-FU-R cells. In addition, 4DPG confers suitable pharmacokinetic properties and strongly abrogates tumor growth, polyps formation, and lung metastasis in an orthotopic rat colorectal carcinoma model. In conclusion, our findings demonstrate 4DPG as a targeted antitumor/anti-metastatic pharmacological lead compound to circumvent EMT-associated drug resistance and suggest its clinical benefits for the treatment of aggressive cancers.

The clinical and molecular characteristics of patients with personal or family history of gastrointestinal malignancies/polyposis and checkpoint kinase 2 (CHEK2) mutations.

44 Background: Checkpoint Kinase 2 (CHEK 2) encodes the protein CHK2, a serine/threonine kinase involved in pathways that conduct DNA repair as well as apoptosis in response to initial DNA damage. Germline mutations in the CHEK2 gene are associated with several malignancies such as colon, breast, stomach, prostate, kidney, thyroid and soft tissue cancers. Here, we describe the clinical and molecular characteristics of patients with personal or family history of gastrointestinal (GI) malignancies/polyposis and CHEK2 gene mutations. Methods: This is an IRB-approved retrospective chart-review study. Between 2016 and 2020, 1011 unique genetic counseling visits were conducted. Germline testing was recommended by a certified genetic counselor if medically necessary. All patients with a germline CHEK2 mutation were identified (N = 16). Patients with a CHEK2 mutation and personal and family history of GI malignancies/polyposis were further explored and their clinical and molecualr characteristics are summarized. Results: The reasons for referral to the Cancer Genetics Counseling Services in patients with pathogenic CHEK2 mutations were personal history of colon cancer (N = 3) and family history of colon cancer (N = 4). One patient with the CHEK2 c.1100delC mutation had a personal history of juvenile polyposis syndrome and a family history of colon cancer. In our cohort, 11 out of 16 (69%) patients had a CHEK2 mutation and personal or family history of GI malignancies/polyposis. The median age was 57 years old (25-80). Six (55%) patients were males. All (100%) patients were Caucasians. Seven (64%) patients had a pathogenic germline CHEK2 mutation and 4 (36%) patients had a variant of unknown significance (VUS). Among patients with pathogenic germline CHEK2 mutations (N = 7), 5 (72%) patients had CHEK2 c.1100delC mutation, 1 (14%) patient had CHEK2 c.190G > A mutation and 1 (14%) patient had CHEK2 c.470T > C mutation. The CHEK2 VUS mutations seen in our cohort were CHEK2 c.539G > A, CHEK2 p.V395L, CHEK2 gain of exons 3-15 and CHEK2 c.1421G > A mutations. Conclusions: All patients in our cohort with CHEK2 mutations were Caucasians. The majority of our patients (69%) had an underlying personal or family history of GI malignancies/polyposis. In patients with personal or family history of GI malignancies/polyposis and CHEK2 mutation, 64% were found to have pathogenic CHEK2 mutations. The most common diagnosed CHEK2 mutation in our cohort was CHEK2 c.1100delC mutation.

A pathway linking translation stress to checkpoint kinase 2 signaling in Neurospora crassa

Checkpoint kinase 2 (CHK-2) is a key component of the DNA damage response (DDR). CHK-2 is activated by the PIP3-kinase-like kinases (PI3KKs) ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related protein (ATR), and in metazoan also by DNA-dependent protein kinase catalytic subunit (DNA-PKcs). These DNA damage-dependent activation pathways are conserved and additional activation pathways of CHK-2 are not known. Here we show that PERIOD-4 (PRD-4), the CHK-2 ortholog of Neurospora crassa, is part of a signaling pathway that is activated when protein translation is compromised. Translation stress induces phosphorylation of PRD-4 by a PI3KK distinct from ATM and ATR. Our data indicate that the activating PI3KK is mechanistic target of rapamycin (mTOR). We provide evidence that translation stress is sensed by unbalancing the expression levels of an unstable protein phosphatase that antagonizes phosphorylation of PRD-4 by mTOR complex 1 (TORC1). Hence, Neurospora mTOR and PRD-4 appear to coordinate metabolic state and cell cycle progression.