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Pictilisib (GDC-0941) is a well-known dual inhibitor of class I PI3K and mTOR and is presently undergoing phase 2 clinical trials for cancer treatment. The present work investigated the dynamic behaviors and interaction mechanism between GDC-0941 and human serum albumin (HSA). Molecular docking and MD trajectory analyses revealed that GDC-0941 bound to HSA and that the binding site was positioned in subdomain IIA at Sudlow's site I of HSA. The fluorescence intensity of HSA was strongly quenched by GDC-0941, and results showed that the HSA–GDC-0941 interaction was a static process caused by ground-state complex formation. The association constant of the HSA–GDC-0941 complex was approximately 105 M−1, reflecting moderate affinity. Thermodynamic analysis conclusions were identical with MD simulation results, which revealed that van der Waals interactions were the vital forces involved in the binding process. CD, synchronous, and 3D fluorescence spectroscopic results revealed that GDC-0941 induced the structural change in HSA. Moreover, the conformational change of HSA affected its molecular sizes, as evidenced by AFM. This work provides a useful research strategy for exploring the interaction of GDC-0941 with HSA, thus helping in the understanding of the transport and delivery of dual inhibitors in the blood circulation system. [ABSTRACT FROM AUTHOR]

Although advances in diagnostics and therapeutics have prolonged the survival of triple-negative breast cancer (TNBC) patients, metastasis, therapeutic resistance, and lack of targeted therapies remain the foremost hurdle in the effective management of TNBC. Thus, evaluation of new therapeutic agents and their efficacy in combination therapy is urgently needed. The thirdgeneration retinoid adapalene (ADA) has potent antitumor activity, and using ADA in combination with existing therapeutic regimens may improve the effectiveness and minimize the toxicities and drug resistance. The current study aimed to assess the anticancer efficacy of adapalene as a combination regimen with the PI3K inhibitor (GDC-0941) in TNBC in vitro models. The Chou-Talalay's method evaluated the pharmacodynamic interactions (synergism, antagonism, or additivity) of binary drug combinations. Flow cytometry, Western blotting, and in silico studies were used to analyze the mechanism of GDC-ADA synergistic interactions in TNBC cells. The combination of GDC and ADA demonstrated a synergistic effect in inhibiting proliferation, migration, and colony formation of tumor cells. Accumulation of reactive oxygen species upon co-treatment with GDC and ADA promoted apoptosis and enhanced sensitivity to GDC in TNBC cells. The findings indicate that ADA is a promising therapeutic agent in treating advanced BC tumors and enhance sensitivity to GDC in inhibiting tumor growth in TNBC models while reducing therapeutic resistance. [ABSTRACT FROM AUTHOR]

Although advances in diagnostics and therapeutics have prolonged the survival of triple-negative breast cancer (TNBC) patients, metastasis, therapeutic resistance, and lack of targeted therapies remain the foremost hurdle in the effective management of TNBC. Thus, evaluation of new therapeutic agents and their efficacy in combination therapy is urgently needed. The third-generation retinoid adapalene (ADA) has potent antitumor activity, and using ADA in combination with existing therapeutic regimens may improve the effectiveness and minimize the toxicities and drug resistance. The current study aimed to assess the anticancer efficacy of adapalene as a combination regimen with the PI3K inhibitor (GDC-0941) in TNBC in vitro models. The Chou–Talalay’s method evaluated the pharmacodynamic interactions (synergism, antagonism, or additivity) of binary drug combinations. Flow cytometry, Western blotting, and in silico studies were used to analyze the mechanism of GDC–ADA synergistic interactions in TNBC cells. The combination of GDC and ADA demonstrated a synergistic effect in inhibiting proliferation, migration, and colony formation of tumor cells. Accumulation of reactive oxygen species upon co-treatment with GDC and ADA promoted apoptosis and enhanced sensitivity to GDC in TNBC cells. The findings indicate that ADA is a promising therapeutic agent in treating advanced BC tumors and enhance sensitivity to GDC in inhibiting tumor growth in TNBC models while reducing therapeutic resistance.

Pictilisib (GDC-0941) is a well-known dual inhibitor of class I PI3K and mTOR and is presently undergoing phase 2 clinical trials for cancer treatment. The present work investigated the dynamic behaviors and interaction mechanism between GDC-0941 and human serum albumin (HSA). Molecular docking and MD trajectory analyses revealed that GDC-0941 bound to HSA and that the binding site was positioned in subdomain IIA at Sudlow’s site I of HSA. The fluorescence intensity of HSA was strongly quenched by GDC-0941, and results showed that the HSA–GDC-0941 interaction was a static process caused by ground-state complex formation. The association constant of the HSA–GDC-0941 complex was approximately 105 M−1, reflecting moderate affinity. Thermodynamic analysis conclusions were identical with MD simulation results, which revealed that van der Waals interactions were the vital forces involved in the binding process. CD, synchronous, and 3D fluorescence spectroscopic results revealed that GDC-0941 induced the structural change in HSA. Moreover, the conformational change of HSA affected its molecular sizes, as evidenced by AFM. This work provides a useful research strategy for exploring the interaction of GDC-0941 with HSA, thus helping in the understanding of the transport and delivery of dual inhibitors in the blood circulation system.

Abstract Background This phase Ib study (NCT00960960) evaluated pictilisib (GDC-0941; pan-phosphatidylinositol 3-kinase inhibitor) plus paclitaxel, with and without bevacizumab or trastuzumab, or in combination with letrozole, in patients with locally recurrent or metastatic breast cancer. Methods This was a three-part multischedule study. Patients in parts 1 and 2, which comprised 3 + 3 dose escalation and cohort expansion stages, received pictilisib (60–330 mg) plus paclitaxel (90 mg/m2) with and without bevacizumab (10 mg/kg) or trastuzumab (2–4 mg/kg). In part 3, patients received pictilisib (260 mg) plus letrozole (2.5 mg). Primary objectives were evaluation of safety and tolerability, identification of dose-limiting toxicities (DLTs) and the maximum tolerated dose (MTD) of pictilisib, and recommendation of a phase II dosing regimen. Secondary endpoints included pharmacokinetics and preliminary antitumor activity. Results Sixty-nine patients were enrolled; all experienced at least one adverse event (AE). Grade ≥ 3 AEs, serious AEs, and AEs leading to death were reported in 50 (72.5%), 21 (30.4%), and 2 (2.9%) patients, respectively. Six (8.7%) patients reported a DLT, and the MTD and recommended phase II pictilisib doses were established where possible. There was no pictilisib–paclitaxel drug–drug interaction. Two (3.4%) patients experienced complete responses, and 17 (29.3%) patients had partial responses. Conclusions Combining pictilisib with paclitaxel, with and without bevacizumab or trastuzumab, or letrozole, had a manageable safety profile in patients with locally recurrent or metastatic breast cancer. The combination had antitumor activity, and the additive effect of pictilisib supported further investigation in a randomized study. Trial registration ClinicalTrials.gov, NCT00960960. Registered on August 13, 2009.

Aim: Herein is presented the combined effect of PI3K inhibitor (GDC-0941) and CXCR1/2 analogue (G31P) in breast cancer. Materials & methods: Breast cancer cell lines and xenograft model were employed to test the efficacy of the combination therapy. Results: GDC-0941+G31P treatment substantially inhibited multiplication of all the breast cancer cell lines used in this study (BT474, HCC1954 and 4T1). Even though single therapies caused a meaningful S-phase cell cycle arrest, the inhibition effect was more potent with the combined treatment. Similarly, enhanced apoptosis accompanied GDC-0941+G31P treatment. Furthermore, the migration ability of the breast cancer cell lines were significantly curtailed by the combination therapy compared with the single treatments. Conclusion: The findings suggest that combination treatment involving PI3K inhibitor and CXCR1/2 analogue (G31P) could be a potent therapeutic option for breast cancer treatment. [ABSTRACT FROM AUTHOR]

Abstract: Aberrant receptor kinase signalling and tumour neovascularization are hallmarks of medulloblastoma development and are both considered valuable therapeutic targets. In addition to VEGFR1/2, expression of PDGFR α/β in particular has been documented as characteristic of metastatic disease correlating with poor prognosis. Therefore, we have been suggested that the clinically approved multi‐kinase angiogenesis inhibitor Axitinib, which specifically targets these kinases, might constitute a promising option for medulloblastoma treatment. Indeed, our results delineate anti‐neoplastic activity of Axitinib in medulloblastoma cell lines modelling the most aggressive c‐myc‐amplified Non‐WNT/Non‐SHH and SHH‐TP53‐mutated tumours. Exposure of medulloblastoma cell lines to Axitinib results in marked inhibition of proliferation and profound induction of cell death. The differential efficacy of Axitinib is in line with target expression of medulloblastoma cells identifying VEGFR 1/2, PDGFR α/β and c‐kit as potential markers for drug application. The high specificity of Axitinib and the consequential low impact on the haematopoietic and immune system render this drug ideal multi‐modal treatment approaches. In this context, we demonstrate that the clinically available PI3K inhibitor GDC‐0941 enhances the anti‐neoplastic efficacy of Axitinib against c‐myc‐amplified medulloblastoma. Our findings provide a rational to further evaluate Axitinib alone and in combination with other therapeutic agents for the treatment of most aggressive medulloblastoma subtypes. [ABSTRACT FROM AUTHOR]

Hyperactivation of the PI3K pathway has been implicated in resistance to antiestrogen therapies in estrogen receptor a (ER)-positive breast cancer, prompting the development of therapeutic strategies to inhibit this pathway. Autophagy has tumor-promoting and -suppressing roles and has been broadly implicated in resistance to anticancer therapies, including antiestrogens. Chloroquine (CQ) is an antimalarial and amebicidal drug that inhibits autophagy in mammalian cells and human tumors. Herein, we observed that CQ inhibited proliferation and autophagy in ER+ breast cancer cells. PI3K inhibition with GDC-0941 (pictilisib) induced autophagy. Inhibition of autophagy using CQ or RNA interference potentiated PI3K inhibitor-induced apoptosis. Combined inhibition of PI3K and autophagy effectively induced mitochondrial membrane depolarization, which required the BH3-only proapoptotic proteins Bim and PUMA. Treatment with GDC-0941, CQ, or the combination, significantly suppressed the growth of ER+ breast cancer xenografts in mice. In an antiestrogen-resistant xenograft model, GDC-0941 synergized with CQ to provide partial, but durable, tumor regression. These findings warrant clinical evaluation of therapeutic strategies to target ER, PI3K, and autophagy for the treatment of ER+ breast cancer. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) is among the most lethal of all human tumors. It is the most frequently occurring malignant primary brain tumor in adults. The current standard of care (SOC) for GBM is initial surgical resection followed by treatment with a combination of temozolomide (TMZ) and ionizing radiation (IR). However, GBM has a dismal prognosis, and survivors have compromised quality of life owing to the adverse effects of radiation. GBM is characterized by overt activity of the phosphoinositide 3-kinase (PI3K) signaling pathway. GDC-0941 is a highly specific PI3K inhibitor with promising anti-tumor activity in human solid tumors. It is being evaluated in Phase II clinical trials for the treatment of breast and non-squamous cell lung cancer. We hypothesized that GDC-0941 may act as an antitumor agent and potentiate the effects of TMZ and IR. In this study, GDC-0941 alone induced cytotoxicity and pro-apoptotic effects. Moreover, combined with the standard GBM therapy (TMZ and IR), it suppressed cell viability, showed enhanced pro-apoptotic effects, augmented autophagy response, and attenuated migratory/invasive capacity in three glioma cell lines. Protein microarray analyses showed that treatment with TMZ+GDC-0941+IR induced higher levels of p53 and glycogen synthase kinase 3-beta (GSK3-β) expression in SHG44GBM cells than those induced by other treatments. This was verified in all cell lines by western blot analysis. Furthermore, the combination of TMZ and GDC-0941 with or without IR reduced the levels of p-AKT and O 6 -methylguanine DNA methyltransferase (MGMT) in T98G cells. The results of this study suggest that the combination of TMZ, IR, and GDC-0941 is a promising choice for future treatments of GBM. [ABSTRACT FROM AUTHOR]

Breast cancer is characterized by high morbidity and mortality. GDC-0941 is a PI3K inhibitor with oncogenic effects in breast cancer. However, certain breast cancer cells are insensitive to GDC-0941. Hence, the mechanism of GDC-0941 in breast cancer resistance was investigated in this study. Breast cancer cell lines BT-474, MCF7, Hs-578-T, MDA-MB-231, MDA-MB-453, and MDA-MB-468 were cultured in different medium and then treated with 100 or 500 nM GDC-0941, 100 nM OSU-T315, or TNF-α antibody. Moreover, ILK and shILK were transfected into cells. The half maximal inhibitory concentrations (IC50) for GDC-0941 were detected using CCK-8 assay. The levels of ILK, AKT, PDK1, S6, and p70S6K expression were detected using western blotting and qPCR. In addition, the mouse model of breast cancer was constructed to measure the tumor size, volume, and weight. The results showed that GDC-0941 decreased cell survival rate, downregulated the phosphorylation of AKT, S6, and p70S6K, and promoted the expression of ILK, while it had little effect on PDK1 expression. GDC-0941 inhibited the increases in p-AKT, p-S6, and p-p70S6K caused by ILK overexpression and promoted ILK knockdown-induced reduction of p-AKT, p-S6, and p-p70S6K. In addition, the combination of OSU-T315 and GDC-0941 decreased p-AKT, p-S6, and p-p70S6K level, tumor volume, and tumor weight. GDC-0941 promoted ILK expression by upregulating TNF-α level. Taken together, GDC-0941 increased ILK level by upregulating TNF-α, thus affecting AKT expression and the sensitivity of breast cancer cells to GDC-0941.

Aberrant receptor kinase signalling and tumour neovascularization are hallmarks of medulloblastoma development and are both considered valuable therapeutic targets. In addition to VEGFR1/2, expression of PDGFR α/β in particular has been documented as characteristic of metastatic disease correlating with poor prognosis. Therefore, we have been suggested that the clinically approved multi-kinase angiogenesis inhibitor Axitinib, which specifically targets these kinases, might constitute a promising option for medulloblastoma treatment. Indeed, our results delineate anti-neoplastic activity of Axitinib in medulloblastoma cell lines modelling the most aggressive c-myc-amplified Non-WNT/Non-SHH and SHH-TP53-mutated tumours. Exposure of medulloblastoma cell lines to Axitinib results in marked inhibition of proliferation and profound induction of cell death. The differential efficacy of Axitinib is in line with target expression of medulloblastoma cells identifying VEGFR 1/2, PDGFR α/β and c-kit as potential markers for drug application. The high specificity of Axitinib and the consequential low impact on the haematopoietic and immune system render this drug ideal multi-modal treatment approaches. In this context, we demonstrate that the clinically available PI3K inhibitor GDC-0941 enhances the anti-neoplastic efficacy of Axitinib against c-myc-amplified medulloblastoma. Our findings provide a rational to further evaluate Axitinib alone and in combination with other therapeutic agents for the treatment of most aggressive medulloblastoma subtypes., (© 2018 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

Hyperactivation of the PI3K pathway has been implicated in resistance to antiestrogen therapies in estrogen receptor α (ER)-positive breast cancer, prompting the development of therapeutic strategies to inhibit this pathway. Autophagy has tumor-promoting and -suppressing roles and has been broadly implicated in resistance to anticancer therapies, including antiestrogens. Chloroquine (CQ) is an antimalarial and amebicidal drug that inhibits autophagy in mammalian cells and human tumors. Herein, we observed that CQ inhibited proliferation and autophagy in ER + breast cancer cells. PI3K inhibition with GDC-0941 (pictilisib) induced autophagy. Inhibition of autophagy using CQ or RNA interference potentiated PI3K inhibitor-induced apoptosis. Combined inhibition of PI3K and autophagy effectively induced mitochondrial membrane depolarization, which required the BH3-only proapoptotic proteins Bim and PUMA. Treatment with GDC-0941, CQ, or the combination, significantly suppressed the growth of ER + breast cancer xenografts in mice. In an antiestrogen-resistant xenograft model, GDC-0941 synergized with CQ to provide partial, but durable, tumor regression. These findings warrant clinical evaluation of therapeutic strategies to target ER, PI3K, and autophagy for the treatment of ER + breast cancer.-Yang, W., Hosford, S. R., Traphagen, N. A., Shee, K., Demidenko, E., Liu, S., Miller, T. W. Autophagy promotes escape from phosphatidylinositol 3-kinase inhibition in estrogen receptor-positive breast cancer.

Medulloblastoma is comprised of at least four molecular subgroups with distinct clinical outcome (WHO classification 2016). SHH-TP53-mutated as well as MYC-amplified Non-WNT/Non-SHH medulloblastoma show the worst prognosis.Here we present evidence that single application of the multi-kinase inhibitor Vandetanib displays anti-neoplastic efficacy against cell lines derived from high-risk SHH-TP53-mutated and MYC-amplified Non-WNT/Non-SHH medulloblastoma. The narrow target spectrum of Vandetanib along with a favourable toxicity profile renders this drug ideal for multimodal treatment approaches. In this context our investigation documents that Vandetanib in combination with the clinically available PI3K inhibitor GDC-0941 leads to enhanced cytotoxicity against MYC-amplified and SHH-TP53-mutated medulloblastoma. In line with these findings we show for MYC-amplified medulloblastoma a profound reduction in activity of the oncogenes STAT3 and AKT. Furthermore, we document that Vandetanib and the standard chemotherapeutic Etoposide display additive anti-neoplastic efficacy in the investigated medulloblastoma cell lines that could be further enhanced by PI3K inhibition. Of note, the combination of Vandetanib, GDC-0941 and Etoposide results in MYC-amplified and SHH-TP53-mutated cell lines in complete loss of cell viability. Our findings therefore provide a rational to further evaluate Vandetanib in combination with PI3K inhibitors as well as standard chemotherapeutics in vivo for the treatment of most aggressive medulloblastoma variants.

Trastuzumab, an anti-ErbB2 humanized antibody, brings benefit to patients with ErbB2-amplified metastatic breast cancers. However, the resistance to trastuzumab is common. Our previously reported H2-18, an anti-ErbB2 antibody, potently induced programmed cell death in trastuzumab-resistant breast cancer cells. Here, we aim to investigate the antitumor efficacy of H2-18 in combination with the pan-PI3K inhibitor GDC-0941 in trastuzumab-resistant breast cancer cell lines. The results showed that H2-18 and GDC-0941 synergistically inhibited the in vitro proliferation of BT-474, SKBR-3, HCC-1954 and HCC-1419 breast cancer cells. H2-18 plus GDC-0941 showed significantly enhanced programmed cell death-inducing activity compared with each drug used alone. The combination of H2-18 and GDC-0941 did not increase the effect of single agent on ROS production, cell cycle and ErbB2 signaling. Importantly, the in vivo antitumor efficacy of H2-18 plus GDC-0941 was superior to that of single agent. Thus, the enhanced in vivo antitumor efficacy of H2-18 plus GDC-0941 may mainly be attributable to its increased programmed cell death-inducing activity. Collectively, H2-18 plus GDC-0941 could effectively inhibit tumor growth, suggesting the potential to be translated into clinic as an efficient strategy for ErbB2-overexpressing breast cancers., Competing Interests: CONFLICTS OF INTEREST The authors declare no conflicts of interest.

The phosphatidylinositol-3 kinase (PI3K)/Akt/mTOR signaling pathway is activated in many human cancers. Previously, we reported that patients with early stage cervical cancer whose tumours harbour PIK3CA exon 9 or 20 mutations have worse overall survival in response to treatment with radiation and cisplatin than patients with wild-type PIK3CA. The purpose of this study was to determine whether PIK3CA-E545K mutation renders cervical cancer cells more resistant to cisplatin and/or radiation, and whether PI3K inhibition reverses the phenotype. We found that CaSki cells that are heterozygous for the PIK3CA-E545K mutation are more resistant to cisplatin or cisplatin plus radiation than either HeLa or SiHa cells that express only wild-type PIK3CA. Similarly, HeLa cells engineered to stably express PIK3CA-E545K were more resistant to cisplatin or cisplatin plus radiation than cells expressing only wild-type PIK3CA or with PIK3CA depleted. Cells expressing the PIK3CA-E545K mutation also had constitutive PI3K pathway activation and increased cellular migration and each of these phenotypes was reversed by treatment with the PI3K inhibitor GDC-0941/Pictilisib. Our results suggests that cervical cancer patients whose tumours are positive for the PIK3CA-E545K mutation may benefit from PI3K inhibitor therapy in concert with standard cisplatin and radiation therapy.

Targeted radioiodine therapy for thyroid cancer is based on selective stimulation of Na+/I- Symporter (NIS)-mediated radioactive iodide uptake (RAIU) in thyroid cells by thyrotropin. Patients with advanced thyroid cancer do not benefit from radioiodine therapy due to reduced or absent NIS expression. To identify inhibitors that can be readily translated into clinical care, we examined oncological pipeline inhibitors targeting Akt, MEK, PI3K, Hsp90 or BRAF in their ability to increase RAIU in thyroid cells expressing BRAFV600E or RET/PTC3 oncogene. Our data showed that (1) PI3K inhibitor GDC-0941 outperformed other inhibitors in RAIU increase mainly by decreasing iodide efflux rate to a great extent; (2) RAIU increase by all inhibitors was extensively reduced by TGF-β, a cytokine secreted in the invasive fronts of thyroid cancers; (3) RAIU reduction by TGF-β was mainly mediated by NIS reduction and could be reversed by Apigenin, a plant-derived flavonoid; and (4) In the presence of TGF-β, GDC-0941 with Apigenin co-treatment had the highest RAIU level in both BRAFV600E expressing cells and RET/PTC3 expressing cells. Taken together, Apigenin may serve as a dietary supplement along with small molecule inhibitors to improve radioiodine therapeutic efficacy on invasive tumor margins thereby minimizing future metastatic events.