Potent Cyclin-dependent Kinase Inhibitor Research Articles

Robust expression of p27Kip1 induced by viral infection is critical for antiviral innate immunity.

Influenza A virus (IAV) infection regulates the expression of numerous host genes. However, the precise mechanism underlying implication of these genes in IAV pathogenesis remains largely unknown. Here, we employed isobaric tags for relative and absolute quantification (iTRAQ) to identify host proteins regulated by IAV infection. iTRAQ analysis of mouse lungs infected or uninfected with IAV showed a total of 167 differentially upregulated proteins in response to the viral infection. Interestingly, we observed that p27Kip1, a potent cyclin-dependent kinase inhibitor, was markedly induced by IAV both at mRNA and protein levels through in vitro and in vivo studies. Furthermore, it was shown that innate immune signalling positively regulated p27Kip1 expression in response to IAV infection. Ectopic expression of p27Kip1 in A549 cells dramatically inhibited IAV replication, whereas, p27Kip1 knockdown significantly enhanced the virus replication. in vivo experiments demonstrated that p27Kip1 knockout (KO) mice were more susceptible to IAV than wild-type (WT) mice: exhibiting higher viral load in lung tissue, faster body-weight loss, reduced survival rate and more severe organ damage. Moreover, we found that p27Kip1 overexpression facilitated the degradation of viral NS1 protein, caused a dramatic STAT1 activation and promoted the expression of IFN-β and several critical antiviral interferon-stimulated genes (ISGs). Increased p27Kip1 expression also restricted infections of several other viruses. Conversely, IAV-infected p27Kip1 KO mice exhibited a sharp increase in NS1 protein accumulation, reduced level of STAT1 activation and decreased expression of IFN-β and the ISGs in the lung compared to WT animals. These findings reveal a key role of p27Kip1 in enhancing antiviral innate immunity.

First-in-human phase I study of SY-5609, an oral, potent, and selective noncovalent CDK7 inhibitor, in adult patients with select advanced solid tumors.

TPS3662 Background: SY-5609 is an oral, noncovalent, highly selective and potent inhibitor of cyclin-dependent kinase 7 (CDK7), a key regulator of 2 biological processes that play critical roles in driving tumor development: transcription and cell cycle control. Evaluation of SY-5609 as a single agent in PDX models from a range of solid tumors, including breast, ovarian, lung and colorectal tumors, revealed robust antitumor activity including complete regressions, and activity in models known to be resistant to standard of care therapy. Models with genetic alterations in RB pathway genes demonstrated deep ( > 90% TGI) and sustained SY-5609-induced tumor regressions following treatment discontinuation, in contrast to models without genetic alteration in RB pathway genes, suggesting that tumor cells with aberrant cell-cycle control may be particularly sensitive to SY-5609 treatment. The study is designed to evaluate the safety, tolerability, and maximum tolerated dose (MTD) of SY-5609, to characterize the pharmacokinetic (PK), pharmacodynamic (PD), and preliminary antitumor activity of SY-5609, and to explore candidate biomarkers predictive of response to SY-5609. Methods: This is a multi-center, open-label Phase 1 trial expected to enroll approximately 60 adult patients with select advanced solid tumors for which standard treatment is no longer effective. The dose escalation phase of the trial is open to adult patients with ovarian, breast, colorectal, or lung cancer, and patients with any solid tumor histology with molecular evidence of deregulated RB cell cycle control. SY-5609 is being administered orally once daily, for each 4-week cycle. Initially, patients will be enrolled into single-patient accelerated titration cohorts; subsequent cohorts will transition to a 3 + 3 design. Following completion of DLT evaluation at a given dose level, additional patients may be enrolled at that dose to further characterize safety, PK, PD, and early clinical activity. Data from this trial will support dose selection for planned evaluations of antitumor activity of SY-5609 as a single agent and in combination. Clinical trial information: NCT04247126 .

Extracellular Vesicle Delivery of TRAIL Eradicates Resistant Tumor Growth in Combination with CDK Inhibition by Dinaciclib.

Tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) is a promising anti-cancer agent that rapidly induces apoptosis in cancer cells. Unfortunately, the clinical application of recombinant TRAIL (rTRAIL) has been hampered by its common cancer resistance. Naturally TRAIL is delivered as a membrane-bound form by extracellular vesicles (EV-T) and is highly efficient for apoptosis induction. SCH727965 (dinaciclib), a potent cyclin-dependent kinase (CDK) inhibitor, was shown to synergize with other drugs to get better efficacy. However, it has never been investigated if dinaciclib coordinates with EV-T to enhance therapeutic results. This study explores the potential of combination therapy with EV-T and dinaciclib for cancer treatment. EV-T was successfully derived from human TRAIL transduced cells and shown to partially overcome resistance of A549 cells. Dinaciclib was shown to drastically enhance EV-T killing effects on cancer lines that express good levels of death receptor (DR) 5, which are associated with suppression of CDK1, CDK9 and anti-apoptotic proteins. Combination therapy with low doses of EV-T and dinaciclib induced strikingly enhanced apoptosis and led to complete regression in A549 tumors without any adverse side effects observed in a subcutaneous xenograft model. Tumor infiltration of mass NK cells and macrophages was also observed. These observations thus indicate that the combination of EV-T with dinaciclib is a potential novel therapy for highly effective and safe cancer treatment.

Inhibition of cyclin-dependent kinases by AT7519 enhances nasopharyngeal carcinoma cell response to chemotherapy.

The poor outcomes in nasopharyngeal carcinoma (NPC) necessitate new treatments. AT7519 is a potent inhibitor of several cyclin-dependent kinases (CDKs) and is currently in the early phase of clinical development for cancer treatment. The potent anti-cancer activities of AT7519 have been reported in various cancers, but not in NPC. The effects of AT7519 in NPC were systematically analyzed using cell culture assays and xenograft mouse models. The effects of AT7519 on molecules involved in mRNA transcription were examined. AT7519, at a nanomolar concentration, significantly inhibits growth via arresting cells at G2/M phase, and induces apoptosis in NPC cells regardless of Epstein-Barr virus (EBV) infection and cellular origin. It also inhibits growth of a subpopulation of cells with highly proliferative and invasive features. Importantly, AT7519 acts synergistically with cisplatin and is effective against chemo-resistant NPC cells. Mechanistically, AT7519 inhibits phosphorylation of Rb, suggesting the inhibition of CDK2 in NPC. It also decreases N-myc level and RNA polymerase II phosphorylation, and inhibits transcription. Consistent with the in vitro findings, we demonstrate that AT7519 is effective asa single agent in two independent NPC xenograft mouse models. The combination of ATP7519 and cisplatin results in greater efficacy than cisplatinalone in inhibiting NPC tumor growth. Our work is the first to report anti-NPC activities of AT7519. Our preclinical evidence suggests that AT7519 is a useful addition to overcome NPC chemo-resistance.

Mechanisms of crude protein from medicinal mushroom Ophiocordyceps sobolifera against human breast MCF-7 cancer cells

The mycelial extract of the entomopathogenic fungus Ophiocordyceps sobolifera has recently been reported to have anti-bacterial, anti-fungal and anti-cancer effects; however, there have been no reports on the medicinal value of the crude protein against the Michigan Cancer Foundation-7 (MCF-7) human breast cancer cell line. Therefore, in this study, crude proteins from 11 isolates of O. sobolifera were subjected to screening and evaluation for potential anticancer activity against a breast cancer cell line. The cytotoxic and antiproliferative effects of the crude proteins on human breast cancer MCF-7 cell line was investigated using the sulforhodamine B (SRB) assay and colony formation. The gene expression and cell cycle-associated protein levels were assayed by reverse transcription-quantitative polymerase chain reaction and western blotting analysis. The results showed that the crude proteins of all isolates had anti-cancer activity in a time- and dose-dependent manner. Among them, isolates Cod-KK1524, Cod-KK1630, Cod-KK1643 and Cod-KS1601 had greater inhibitory effects against cancer cells; therefore, these were chosen for further evaluation of anti-cancer mechanisms. These crude proteins exhibited a potent anticancer effect on the MCF-7 cells by inhibiting colony formation in a dose-dependent manner. Furthermore, the crude proteins significantly decreased the cyclin-dependent kinase 6 (cdk6) and cyclin D1 expression. Additionally, crude proteins significantly enhanced the potent cyclin-dependent kinase inhibitor (p21) levels, and reduced the expression level of the cell cycle protein, cyclin D1. These findings indicate that the crude protein of the entomopathogenic fungus O. sobolifera may be useful for developing an anti-cancer drug candidate for breast cancer therapeutic treatment.

Rapid maturation of the hepatic cell line Huh7 via CDK inhibition for PXR dependent CYP450 metabolism and induction

CYP3A4, a cytochrome P450 enzyme regulated by the nuclear receptor PXR, is involved in most of the drug metabolizing pathways. Studying the regulation/induction of CYP3A4 and PXR is critical in toxicology and drug-drug interaction (DDI) studies. Primary human hepatocytes constitute the preferred in vitro platform for drug development efforts. However, they are expensive, scarce and heterogeneous. Hepatic cell lines, such as Huh7, could provide a cost-effective alternative, however, they express negligible amounts of CYP450s and PXR. In this study, we show that dinaciclib, a potent cyclin dependent kinase inhibitor, significantly increases the basal CYP3A4 and PXR levels in 24 hours. We also demonstrated that matured Huh7s can be used for drug induction studies, where CYP3A4, CYP1A2, CYP2C9, and CYP2C19 inductions were achieved following rifampicin treatment. More importantly, through a direct demonstration using amiodarone and rifampicin as model drugs, we showed that matured Huh7s present a suitable platform for DDI studies.

Analysis of the selection of CDK4/6 inhibitors based on experience using palbociclib

Palbociclib is a first-in-class potent oral inhibitor of cyclin-dependent kinase (CDK)4/6 that was approved in the USA in 2015 and in Japan in 2017. Next-generation abemaciclib was approved in the USA and Japan in 2018. The use of palbociclib results in a high frequency of bone marrow suppression, whereas abemaciclib induces a low frequency of bone marrow suppression, but a high incidence of diarrhea. However, the most appropriate uses for these CDK4/6 inhibitors remain unclear. In this study, we analyzed the efficacy and side-effects associated with the use of palbociclib at our hospital and examined the suitability of palbociclib or abemaciclib. Among 35 patients who used palbociclib at our hospital from December, 2017 to December, 2018, the mean age was 39-83 years. The patients receiving treatment with palbociclib with a combination of drugs included 20 patients (57%) receiving fulvestrant, 8 patients (23%) receiving letrozole, and 7 patients (20%) receiving fulvestrant + LH-RH (leuprorelin). Fourteen patients (40%) had a history of receiving chemotherapy, and 21 patients (60%) had no history of receiving chemotherapy. The number of prior treatment regimens was 0-11 (mean, 2.9). The initial dose of palbociclib was 125 mg for 29 patients (83%) and 100 mg for 6 patients (17%). Partial response, stable disease and progressive disease were achieved in 6 (17%), 19 cases (54%) and 10 cases (29%), respectively. Leukocytopenia was observed in 24 cases, neutropenia was observed in 26 cases, anemia was observed in 13 cases, thrombocytopenia was observed in 15 cases, fatigue was observed in 3 cases and itchy skin was observed in 1 case. When the number of neutrophils prior to palbociclib introduction was <3,000, neutropenia of grade 3 or higher was observed in all cases following palbociclib introduction. Thus, in order to avoid grade 3 or higher neutropenia and to maintain relative dose intensity, abemaciclib treatment may be considered for cases with neutrophils of <3,000 prior to the introduction of a CDK4/6 inhibitor.

Targeting CDK12-mediated transcription regulation in anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is the most aggressive type of thyroid cancer, with no effective treatment available. Identification of new anti-ATC drugs represents an urgent need. In this study, we find that ATC cells are highly sensitive to THZ531, a potent inhibitor of the transcriptional cyclin-dependent kinase (CDK), CDK12. Cell-based assays demonstrate that CDK12 inhibition significantly impedes cell cycle progression, induces apoptotic cell death, and impairs colony formation in ATC cells. THZ531 causes a loss of elongating RNA polymerase II and suppresses gene expression in ATC cells. An integrative analysis of gene expression profiles and super-enhancer landscape, combining with functional assays, leads to the discovery of two new ATC cancer genes, ZC3H4 and NEMP1. Furthermore, CDK12 inhibition enhances the sensitivity of ATC cells to doxorubicin-mediated chemotherapy. Thus, these findings indicate that CDK12 is a potential therapeutic target for ATC treatment and its inhibition may help to overcome the chemoresistance in patients with ATC.

Abstract 3642: Combination nanotherapy using the PARP inhibitor talazoparib and cyclin dependent kinase inhibitor dinaciclib

Abstract Introduction: PARP inhibitors exploit defects in DNA repair pathways to selectively target cancerous cells. As such, Talazoparib (TLZ), a potent PARP inhibitor, offers a way to target the biology of a number of cancers with DNA repair defects until these tumors develop resistance. PARP inhibitors must be used in combination with other inhibitors or chemotherapeutics to reverse resistance and sensitize non-responsive tumors. Dinaciclib, a potent cyclin dependent kinase (CDK) inhibitor, has been shown to sensitize both BRCA wild-type tumors and PARP inhibitor resistant tumors to PARP inhibition through disruption of homologous recombination. In clinical trials, Talazoparib and Dinaciclib have both demonstrated hematologic toxicities, suggesting a combination of these drugs would result in compounded toxicity, leading to dose reduction and an ineffective combination. Nanoparticle delivery systems offer a means to modify the toxicity profiles of these drugs and enhance the therapeutic window, therefore allowing for effective combination treatment. Methods: Separate nanoformulations of Talazoparib (NanoTLZ) and Dinaciclib (NanoDCB) were optimized, and pharmacokinetics and pharmacodynamics assessed. Nanoformulations were tested alone and in combination in vitro to ensure NanoDCB could sensitize a model with no known DNA repair defects to NanoTLZ. The combination of the two nanoformulations was then assessed for efficacy and toxicity in orthotopic MDA-MB-231 xenografts. Results: Robust formulations of NanoTLZ and NanoDCB were developed. Each nanoformulation extended the half-life of the drug it encapsulates. A constant low dose of Dinaciclib sensitized MDA-MB-231 cells to Talazoparib, significantly lowering the IC50 value. As a single agent NanoDCB was more effective in vitro than free Dinaciclib. In vivo, the combination of the two nanoformulations was more effective than either single nanoformulation or the combination of the two free drugs. Assessments of hematologic toxicities are underway, but thus far, there were no signs of gross toxicity in the combination therapy group. Conclusions: The combination of NanoDCB and NanoTLZ has provided an effective method for sensitizing tumors to PARP inhibition that are otherwise nonresponsive to this therapy. The development of two separate nanoformulations has allowed for tailored dosing. These long-circulating nanoformulations have proven more effective than the free drugs in stabilizing tumor growth and were well tolerated. This work was supported by ARMY/W81XWH-16-1-0731. Citation Format: Paige Baldwin, Adrienne Orriols, Srinivas Sridhar. Combination nanotherapy using the PARP inhibitor talazoparib and cyclin dependent kinase inhibitor dinaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3642.

Efficacy of the novel CDK7 inhibitor QS1189 in mantle cell lymphoma

Mantle cell lymphoma (MCL) is typically an aggressive and rare form of non-Hodgkin lymphoma (NHL) with a poor prognosis despite recent advances in immunochemotherapy and targeted therapeutics against NHL. New therapeutic agents are needed for MCL. In this study, we generated a potent inhibitor of cyclin-dependent kinase 7 (CDK7), designated QS1189, and confirmed its anti-cancer effects towards MCL and other lymphomas. QS1189 was highly selective for CDK7 and showed potent anticancer effects in MCL compared to other targeted therapeutic agents, such as ibrutinib and venetoclax. Consistent with a conventional CDK7 inhibitor, QS1189 treatment significantly decreased phosphorylation of the carboxyl-terminal domain of RNA polymerase II and transcription-associated genes. QS1189 induced cell cycle arrest at the G2/M phase and apoptosis. Interestingly, QS1189 overcame the acquired resistance to venetoclax, which is mediated by Bcl-xL. Similarly, QS1189 showed potent tumour cell growth inhibition of various lymphomas. Thus, CDK7 might be a suitable therapeutic target for inhibiting lymphoma, and QS1189 is a promising therapeutic option for various lymphomas and cells with acquired resistance to targeted therapy.

Comparing effects of CDK inhibition and E2F1/2 ablation on neuronal cell death pathways in vitro and after traumatic brain injury

Traumatic brain injury (TBI) activates multiple neuronal cell death mechanisms, leading to post-traumatic neuronal loss and neurological deficits. TBI-induced cell cycle activation (CCA) in post-mitotic neurons causes regulated cell death involving cyclin-dependent kinase (CDK) activation and initiation of an E2F transcription factor-mediated pro-apoptotic program. Here we examine the mechanisms of CCA-dependent neuronal apoptosis in primary neurons in vitro and in mice exposed to controlled cortical impact (CCI). In contrast to our prior work demonstrating robust neuroprotective effects by CDK inhibitors after TBI, examination of neuronal apoptotic mechanisms in E2F1−/−/E2F2−/− or E2F2−/− transgenic mice following CCI suggests that E2F1 and/or E2F2 likely play only a modest role in neuronal cell loss after brain trauma. To elucidate more critical CCA molecular pathways involved in post-traumatic neuronal cell death, we investigated the neuroprotective effects and mechanisms of the potent CDK inhibitor CR8 in a DNA damage model of cell death in primary cortical neurons. CR8 treatment significantly reduced caspase activation and cleavage of caspase substrates, attenuating neuronal cell death. CR8 neuroprotective effects appeared to reflect inhibition of multiple pathways converging on the mitochondrion, including injury-induced elevation of pro-apoptotic Bcl-2 homology region 3 (BH3)-only proteins Puma and Noxa, thereby attenuating mitochondrial permeabilization and release of cytochrome c and AIF, with reduction of both caspase-dependent and -independent apoptosis. CR8 administration also limited injury-induced deficits in mitochondrial respiration. These neuroprotective effects may be explained by CR8-mediated inhibition of key upstream injury responses, including attenuation of c-Jun phosphorylation/activation as well as inhibition of p53 transactivation of BH3-only targets.

Synergistic combination of flavopiridol and carfilzomib targets commonly dysregulated pathways in adrenocortical carcinoma and has biomarkers of response.

Drug repurposing is an effective approach to identify active drugs with known toxicity profiles for rare cancers such as ACC. The objective of this study was to determine the anticancer activity of combination treatment for ACC from previously identified candidate agents using quantitative high-throughput screening (qHTS). In this study, we evaluated the anticancer activity of flavopiridol and carfilzomib in three ACC cell lines in vitro and in vivo. Human ACC samples were analyzed for drug-target analysis, and cancer-related pathway arrays were used to identify biomarkers of treatment response. Because flavopiridol is a potent cyclin-dependent kinase (CDK) inhibitor, we found significantly higher CDK1 and CDK2 mRNA expression in three independent cohorts human ACC (p<0.01) and CDK1 protein by immunohistochemistry (p<0.01) in human ACC samples. In vitro treatment with flavopiridol and carfilzomib in all three ACC cell lines resulted in a dose-dependent, anti-proliferative effect, and the combination had synergistic activity as well as in three-dimensional tumor spheroids. We observed increased G2M cell-cycle arrest and apoptosis with combination treatment compared to other groups in vitro. The combination treatment decreased XIAP protein expression in ACC cell lines. Mice with human ACC xenografts treated with flavopiridol and carfilzomib had significantly lower tumor burden, compared to other groups (p<0.05). We observed increased cleaved-caspase expression and decreased XIAP in tumor xenografts of mice treated with combined agents. Our preclinical data supports the evaluation of combination therapy with flavopiridol and carfilzomib in patients with advanced ACC.

Phase 1 safety, pharmacokinetic and pharmacodynamic study of the cyclin-dependent kinase inhibitor dinaciclib administered every three weeks in patients with advanced malignancies

Background:Dinaciclib is a potent inhibitor of cell cycle and transcriptional cyclin-dependent kinases. This Phase 1 study evaluated the safety, tolerability and pharmacokinetics of various dosing schedules of dinaciclib in advanced solid tumour patients and assessed pharmacodynamic and preliminary anti-tumour activity.Methods:In part 1, patients were enrolled in escalating cohorts of 2-h infusions administered once every 3 weeks, utilising an accelerated titration design until a recommended phase 2 dose (RP2D) was defined. In part 2, 8- and 24-h infusions were evaluated. Pharmacokinetic parameters were determined for all schedules. Pharmacodynamic effects were assessed with an ex vivo stimulated lymphocyte proliferation assay performed in whole blood.Effects of dinaciclib on retinoblastoma (Rb) phosphorylation and other CDK targets were evaluated in skin and tumour biopsies. In addition to tumour size, metabolic response was evaluated by 18F-fluorodeoxyglucose-positron emission tomography.Results:Sixty-one patients were enrolled to parts 1 and 2. The RP2Ds were 50, 7.4 and 10.4 mg m−2 as 2- 8- and 24-hour infusions, respectively. Dose-limiting toxicities included pancytopenia, neutropenic fever, elevated transaminases, hyperuricemia and hypotension. Pharmacokinetics demonstrated rapid distribution and a short plasma half-life. Dinaciclib suppressed proliferation of stimulated lymphocytes. In skin and tumour biopsies, dinaciclib reduced Rb phosphorylation at CDK2 phospho-sites and modulated expression of cyclin D1 and p53, suggestive of CDK9 inhibition. Although there were no RECIST responses, eight patients had prolonged stable disease and received between 6 and 30 cycles. Early metabolic responses occurred.Conclusions:Dinaciclib is tolerable at doses demonstrating target engagement in surrogate and tumour tissue.

Abstract 1078: Dinaciclib overcomes resistance to BKM120 in triple negative breast cancer patient-derived xenograft models

Abstract Purpose: Triple negative breast cancer (TNBC) is one of the most lethal subtypes of breast cancer with limited therapeutic options. Development of molecularly targeted agents for TNBC is an unmet clinical need. The phosphoinositide 3-kinase (PI3K) pathway, which is a major cell growth and survival pathway, is frequently activated in TNBC as a result of genetic aberrations such as loss of the negative regulator PTEN or gain of function mutations in PIK3CA, therefore an attractive therapeutic target. However, single agent PI3K inhibitors have shown limited anti-tumor activity in both preclinical models and in clinical trials. One of the most important mechanisms of resistance to PI3K inhibitor is amplification of Myc. Dinaciclib, a potent inhibitor of cyclin-dependent kinases (CDKs)1, 2, 5 and 9, has shown to be particularly effective in Myc dependent tumors in preclinical studies and in TNBC. We therefore hypothesized that dinaciclib could overcome tumor cell resistance to PI3K inhibitors and improve the therapeutic efficacy in TNBC. In this study, we evaluated the anti-tumor and molecular effect of dinaciclib and BKM120 (Pan-PI3K inhibitor), either alone or in combination, in a panel of patient derived xenograft (PDX) models of TNBC. Methods: Four TNBC PDXs models were selected for the study for in-vivo and ex-vivo response to vehicle, BKM120, dinaciclib, or the combination of BKM120 and dinaciclib. Tumor volume changes over time in each group were documented to calculate the percentage of tumor growth inhibition by either agent alone or in combination. Tumor tissues harvested post treatment were examined by immunohistochemistry for cleaved PARP to determine the extent of apoptosis and phospho-Histone H3 for G2 to M phase cell cycle progression. Western blot analysis and reverse protein phase array (RPPA) were also performed to determine treatment effect on PI3K downstream targets and cell cycle molecules. Results: The combination of BKM120 and dinaciclib induced significantly greater growth inhibitory effect on tumor growth than either single agent alone in TNBC PDX models. This is accompanied by an enhanced apoptotic induction and reduced cell cycle progression. In addition, the combination of dinaciclib and BKM120 significantly reduced the level of cyclin B and the key anti-apoptotic protein survivin as well as significant downregulation of pAKT, and pS6. Conclusions: These data suggest that dinaciclib and BKM120 combination is an effective approach in treating TNBC. Additional mechanistic investigation for the efficacy of this combination is underway. Citation Format: Sandeep Rajput, Fang Guo, Li Shun, Cynthia Ma. Dinaciclib overcomes resistance to BKM120 in triple negative breast cancer patient-derived xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1078. doi:10.1158/1538-7445.AM2017-1078

Cell Surface Expression of 70 KDa Heat Shock Proteins and P21 in Normal Oral Mucosa , Oral Epithelial Dysplasia and Squamous Cell Carcinoma : An Immunohistochemical Study

Background: Oral SCC is a complex malignancy where environmental factors, viral infections and genetic alterations most likely interact, and thus give rise to the malignant condition. The HSP70 play a direct role in apoptosis inhibition by aligning the improved integrity of a cell’s proteins with the improved chances of that particular cell’s survival.P21 gene produces p21 protein which is a potent cyclin-dependent kinase inhibitor that plays a significant role in carcinogenesis. The aims of the study were to evaluate and compare the immun-histochemical expression of the HSP70 and cell cycle protein p21in NOM, OED, and OSCC. Correlate both marker expressions with each other. Materials and methods: Forty six formalin-fixed, paraffin embedded tissue blocks(10 cases of normal oral mucosa,16 cases of oral epithelial dysplasia, and 20 cases of oral squamous cell carcinoma) were included in this study, an immunohistochemical staining was performed using antiHSP70monoclonalantibody, and anti p21 monoclonal antibody. Results: Positive IHC expression ofHSP70 was found in 2 cases (20%) of NOM, 13 cases (81.3%) of OED and in 16 cases (85%) of OSCC. Positive IHC expression of P21 was detected In NOM in 2 cases (20%), while it was found in 9 cases (56.2%) of OED, and in 14 cases (70%) of OSCC .The difference between the expressions of both markers was statistically significant in NOM, highly significant in OED, and OSCC. Conclusions: This study signify the important role of HSP70 and p21in oral carcinogenesis and in the evolution of the mucosa from normal to dysplastic to invasive carcinoma

Abstract 1167: Cytoplasmic p21WAF1/CIP1 increases metastatic melanoma survival upon chemotherapy

Abstract Initially described as a potent cyclin-dependent kinase inhibitor and thus a negative regulator of cell cycle, p21waf1/cip1 is a protein whose expression is often altered in cancer. Paradoxically, its upregulation has been correlated with aggressiveness and poor prognosis. p21waf1/cip1 fits the definition of antagonistic duality, since its cytoplasmic functions differ from its nuclear tasks. Our group had previously developed a murine melanoma progression model, which culminated in the establishment of cell lines representing different stages in melanoma genesis. Surprisingly, we detected overexpression of p21waf1/cip1 protein in a metastatic melanoma cell line (4C11+), which exhibits highly aggressive behavior. Despite its aberrant overexpression has already been described in melanoma, including metastases, little is known about the impact of its ectopic overexpression in melanoma aggressiveness. We performed viral-mediated overexpression and downregulation of p21waf1/cip1 in the non-metastatic melanoma lineage (4C11-) which does not express this protein and in the metastatic melanoma cell line (4C11+), respectively, and assessed for its impact on melanoma survival upon Dacarbazine treatment. Flow cytometry analyses were conducted to investigate p21waf1/cip1 cell cycle control in these lineages. Through Western blot analysis, we also evaluated the expression of phospho-Akt and phospho-p21 as well as p21waf1/cip1 subcellular localization, in an attempt to investigate the mechanisms underlying ectopic location of p21waf1/cip1 and thus its oncogenic activities. Our research shows that upregulated cytoplasmic p21waf1/cip1 increases metastatic melanoma survival upon Dacarbazine treatment, which can be reverted by p21waf1/cip1 silencing. We also detected high levels of phospho-Akt(Ser473) and phospho-p21(Thr145), which are determinant in promoting p21waf1/cip1 cytoplasmic retention. Using Wortmannin, a PI3K inhibitor that prevents Akt activation, cytoplasmic p21waf1/cip1 level was substantially diminished. Importantly, we identified high levels of p21waf1/cip1 and phospho-p21waf1/cip1 in patients-derived metastatic melanoma cells. We provided new insights about molecular pathways involved in Dacarbazine-associated resistance in melanomas, pointing p21waf1/cip1 and PI3K/Akt as key contributors in this process. Altogether, our findings contribute to not only design new therapeutic approaches against metastatic melanoma, but also help to elucidate the contradictory and complex role exerted by p21waf1/cip1 in cancer. Supported by FAPESP and CNPq Citation Format: Gabriela Nana Colaneri, Adriana Taveira Cruz, Débora CP Silva, Roberta Sessa Stilhano, Sang Won Han, Miriam G. Jasiulionis. Cytoplasmic p21WAF1/CIP1 increases metastatic melanoma survival upon chemotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1167.

Abstract CT153: Pharmacokinetic drug interactions between abemaciclib and CYP3A inducers and inhibitors

Abstract Abemaciclib is a selective and potent small-molecule inhibitor of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6) being investigated for treatment of refractory hormone-receptor positive (HR+) advanced or metastatic breast cancer. In vitro, CYP3A is responsible for &amp;gt;99% of the CYP-mediated microsomal metabolism of abemaciclib and its active metabolites. Three clinical studies evaluated the disposition and metabolism and drug interaction potential of abemaciclib in the presence of a strong CYP3A-inducer, rifampin, or a strong CYP3A-inhibitor, clarithromycin. Abemaciclib disposition and metabolism were determined following a single oral 150 mg dose of [14C]-abemaciclib in healthy subjects (N = 6). In the rifampin interaction study, abemaciclib was administered as a single oral 200 mg dose in healthy subjects (N = 24) on 2 occasions: alone on Day 1 of Period 1 and in combination with 600 mg rifampin on Day 7 of Period 2, after 6 days of rifampin once daily (QD) dosing; rifampin continued QD for 7 days after abemaciclib. In the clarithromycin interaction study, abemaciclib was administered as a single oral 50 mg dose in patients with advanced cancer (N = 26) on 2 occasions: alone in Period 1 and on Day 5 of clarithromycin dosing (500 mg BID) in Period 2 followed by an additional 7 days of clarithromycin. Abemaciclib was extensively metabolized, with less than 10% of parent drug recovered unchanged in feces. Parent drug and 3 active metabolites; (LSN2839567 [M2], LSN3106729 [M18], and LSN3106726 [M20]) were detected in plasma. The mean t1/2 in healthy subjects was 29.0, 104.0, 55.9, and 43.1 hours for abemaciclib, M2, M18, and M20, respectively. Coadministration with rifampin compared to abemaciclib alone decreased abemaciclib AUC(0-?) and Cmax by 95% and 92%, respectively, and decreased AUC(0-?) and Cmax of total active species (abemaciclib + M2 + M18+ M20) by 77% and 45%, respectively. Coadministration with clarithromycin compared to abemaciclib alone increased abemaciclib AUC(0-?) and Cmax by 237% and 30%, respectively; and increased the total active species AUC(0-?) by 119% and decreased Cmax by 7%. The mean abemaciclib t1/2 was prolonged from 28.8 to 63.6 hours. No clinically significant safety concerns were observed following single doses of abemaciclib in healthy subjects or in patients with advanced cancer based on vital signs, clinical laboratory evaluations, and electrocardiogram data. The human absorption, distribution, metabolism and excretion study indicated that abemaciclib was cleared primarily by hepatic metabolism, and the clinical drug-drug interaction studies with strong CYP3A inducer and inhibitor substantiated the major role of CYP3A in the metabolism of abemaciclib. Due to significant changes in abemaciclib and active-metabolite exposure in the presence of strong CYP3A inducers and inhibitors, concomitant use with abemaciclib should be avoided, or abemaciclib dose may require adjustment. Citation Format: Palaniappan Kulanthaivel, Daruka Mahadevan, P. Kellie Turner, Jane Royalty, Wee Teck Ng, Ping Yi, Jessica Rehmel, Kenneth Cassidy, Jill Chappell. Pharmacokinetic drug interactions between abemaciclib and CYP3A inducers and inhibitors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT153.

Abstract CT152: Food effect on the pharmacokinetics of 200-mg abemaciclib in healthy subject

Abstract Abemaciclib is an oral, selective, and potent small-molecule inhibitor of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6) being investigated for the treatment of patients with refractory hormone-receptor positive (HR+) advanced or metastatic breast cancer. The absolute bioavailability and effect of food on pharmacokinetics (PK) following a single 200-mg oral dose of abemaciclib in healthy subjects were evaluated in three studies (Table 1). Abemaciclib plasma concentrations were measured serially pre-dose through 192 hours post-dose. Non-compartmental analysis was used to calculate PK parameters, and a mixed-effects model was used for statistical inference. In Study 1 the absolute bioavailability of a 200-mg dose of abemaciclib was 45% (90% CI: 40%, 51%). In Study 2 the ratios of AUC0-? after a high-fat or standard meal compared to fasting showed no effect (90% CIs within 0.80, 1.25). However, Cmax increased by 24% and 25% following high-fat and standard meals, respectively, compared to fasting (upper 90% CIs &amp;gt;1.25). No differences were found in the AUC0-? and Cmax of abemaciclib following a high-fat meal compared to a standard meal (90% CI within 0.80, 1.25). The median tmax was delayed by 2 hours following a high-fat meal compared to fasting (p = 0006). However, there was no difference in median tmax between the standard meal and fasting (p = .7197). Abemaciclib terminal half-life was similar across fed and fasted conditions. The late-breaking Study-3 results will be presented. In conclusion, abemaciclib oral bioavailability is sufficient to achieve therapeutic exposure. Food with abemaciclib does not reduce or increase the inter-individual PK variability and does not have a clinically-relevant impact on the PK of abemaciclib. Therefore, abemaciclib may be administered without regard to food. Table 1Designs for three open-label clinical studies of abemaciclib as a single 200-mg oral dose administered to healthy subjectsStudy ParametersNCT02327143a (Study 1)I3Y-MC-JPBSNCT02059148a (Study 2)I3Y-MC-JPBGNCT02482935a (Study 3)I3Y-MC-JPBUCompleted subjects (N)82329Overall designs and formulationsAbsolute bioavailability, 4 x 50-mg (25% w/w) capsules and tracer IVbPilot food effect, randomized crossover 3 period, 6 sequence 4 x 50-mg (50% w/w) capsulesPivotal food effect, randomized crossover 2 period, 2 sequence 2 x 100-mg (25% w/w) capsulesMeal conditionFastedFastedStandard mealHigh-fat, high-calorie mealFastedHigh-fat, high-calorie meal Citation Format: Kellie Turner, Jill Chappell, Palaniappan Kulanthaivel, Wee Teck Ng, Jane Royalty. Food effect on the pharmacokinetics of 200-mg abemaciclib in healthy subject. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT152.

Binding mechanism of CDK5 with roscovitine derivatives based on molecular dynamics simulations and MM/PBSA methods

Roscovitine derivatives are potent inhibitors of cyclin-dependent kinase 5 (CDK5), but they exhibit different activities, which has not been understood clearly up to now. On the other hand, the task of drug design is difficult because of the fuzzy binding mechanism. In this context, the methods of molecular docking, molecular dynamics (MD) simulation, and binding free energy analysis are applied to investigate and reveal the detailed binding mechanism of four roscovitine derivatives with CDK5. The electrostatic and van der Waals interactions of the four inhibitors with CDK5 are analyzed and discussed. The calculated binding free energies in terms of MM-PBSA method are consistent with experimental ranking of inhibitor effectiveness for the four inhibitors. The hydrogen bonds of the inhibitors with Cys83 and Lys33 can stabilize the inhibitors in binding sites. The van der Waals interactions, especially the pivotal contacts with Ile10 and Leu133 have larger contributions to the binding free energy and play critical roles in distinguishing the variant bioactivity of four inhibitors. In terms of binding mechanism of the four inhibitors with CDK5 and energy contribution of fragments of each inhibitor, two new CDK5 inhibitors are designed and have stronger inhibitory potency.

5-Substituted 3-isopropyl-7-[4-(2-pyridyl)benzyl]amino-1(2)H-pyrazolo[4,3-d]pyrimidines with anti-proliferative activity as potent and selective inhibitors of cyclin-dependent kinases

A series of 5-substituted 3-isopropyl-7-[4-(2-pyridyl)benzyl]amino-1(2)H-pyrazolo[4,3-d]pyrimidine derivatives was synthesized and evaluated for their cyclin-dependent kinase (CDK) inhibition activity. The most potent compounds contained various hydroxyalkylamines at the 5 position and possessed low nanomolar IC50 values for CDK2 and CDK5. Preliminary profiling of one of the most active compounds on a panel of 50 protein kinases revealed its high selectivity for CDKs. The compounds arrested cells in S and G2/M phases, and induced apoptosis in various cancer cell lines. Significant dephosphorylation of the C-terminus of RNA polymerase II and focal adhesion kinase (FAK), well-established substrates of CDKs, has been found in treated cells. Cleavage of PARP-1, down-regulation of Mcl-1 and activation of caspases correlated well with CDK inhibition and confirmed apoptosis as the primary type of cell death induced in cancer cells treated with the compounds in vitro. A comparison of known purine-based CDK inhibitor CR8 with its pyrazolo[4,3-d]pyrimidine bioisosteres confirmed that the novel compounds are more potent in cellular assays than purines. Therefore, pyrazolo[4,3-d]pyrimidine may emerge as a novel scaffold in medicinal chemistry and as a source of potent CDK inhibitors.