Identification of fibrocyte cluster in tumors reveals the role in antitumor immunity by PD-L1 blockade.

Recent clinical trials revealed that immune checkpoint inhibitors and antiangiogenic reagent combination therapy improved the prognosis of various cancers. We investigated the roles of fibrocytes, collagen-producing monocyte-derived cells, in combination immunotherapy. Anti-VEGF (vascular endothelial growth factor) antibody increases tumor-infiltrating fibrocytes and enhances the antitumor effects of anti-PD-L1 (programmed death ligand 1) antibody in vivo. Single-cell RNA sequencing of tumor-infiltrating CD45+ cells identifies a distinct "fibrocyte cluster" from "macrophage clusters" in vivo and in lung adenocarcinoma patients. A sub-clustering analysis reveals a fibrocyte sub-cluster that highly expresses co-stimulatory molecules. CD8+ T cell-costimulatory activity of tumor-infiltrating CD45+CD34+ fibrocytes is enhanced by anti-PD-L1 antibody. Peritumoral implantation of fibrocytes enhances the antitumor effect of PD-L1 blockade in vivo; CD86-/- fibrocytes do not. Tumor-infiltrating fibrocytes acquire myofibroblast-like phenotypes through transforming growth factor ß (TGF-ß)/small mothers against decapentaplegic (SMAD) signaling. Thus, TGF-ßR/SMAD inhibitor enhances the antitumor effects of dual VEGF and PD-L1 blockade by regulating fibrocyte differentiation. Fibrocytes are highlighted as regulators of the response to programmed death 1 (PD-1)/PD-L1 blockade.

Effect of Bevacizumab on a Human Breast Cancer Model that Exhibited Palbociclib-resistance by RB Knockout.

BACKGROUND/AIM: Although CDK4/6 inhibitors have been increasingly used in combination with hormonal agents to treat hormone-receptor positive and human epithelial growth factor receptor 2-negative breast cancer, the mechanism of CDK4/6 inhibitor resistance and its impact on established therapy for post-resistance, especially bevacizumab combined with chemotherapy, are unclear. MATERIALS AND METHODS: Sensitivity of RB knockout MCF7 clones to CDK4/6 inhibitors was evaluated in vitro. One RB knockout clone was subcutaneously implanted in nude mice and the effects of bevacizumab on volume and microvessel density (MVD) of tumors were investigated. RESULTS: Palbociclib did not exhibit antitumor efficacy against the RB knockout tumor, in contrast to the parental MCF7 xenograft model. Bevacizumab significantly exhibited antitumor efficacy and suppressed the MVD both in RB knockout and parental MCF7 xenograft models. CONCLUSION: Bevacizumab inhibited tumor growth by suppressing MVD in the CDK4/6 inhibitor-resistant tumor acquired due to RB loss, suggesting its efficacy also in patients after treatment with CDK4/6 inhibitors.

Coadministration with bendamustine restores the antitumor activity of obinutuzumab in obinutuzumab-resistant tumors.

BACKGROUND: The glycoengineered, humanized anti-CD20 antibody obinutuzumab is indicated for previously untreated or relapsed/refractory CD20-positive follicular lymphoma (FL). However, the effectiveness of obinutuzumab retreatment in relapsed/refractory FL after prior obinutuzumab-containing therapy is unclear. To address this issue, we investigated the antitumor activity of obinutuzumab plus bendamustine in obinutuzumab-resistant tumors established from a human non-Hodgkin lymphoma xenograft model. MATERIALS AND METHODS: Obinutuzumab-resistant tumors (SU-DHL-4-OR-18-8) were established from an SU-DHL-4 xenograft model by repeated administration of obinutuzumab. Antitumor activity was evaluated based on tumor volume after treatment with obinutuzumab on Day 1, 8, and 15 and/or bendamustine on Day 1 and 2. Intratumoral natural killer (NK) cells/macrophages were evaluated by immunohistochemistry and flow cytometry. RESULTS: In SU-DHL-4-OR-18-8 xenografted tumors, intratumoral NK cells/macrophages after obinutuzumab treatment were significantly decreased compared with parent tumors on Day 4. The endoplasmic reticulum stress sensor phospho-IRE1 was also decreased. In SU-DHL-4-OR-18-8 tumors, bendamustine treatment increased phospho-IRE1 on Day 4 and intratumor NK cells/macrophages on Day 10. Obinutuzumab combined with bendamustine significantly increased antitumor activity compared with each single agent on Day 29, with an increase in chemoattractant CCL6 expression on Day 10. CONCLUSIONS: Coadministration of bendamustine in obinutuzumab retreatment may be effective against obinutuzumab-resistant tumors.

Resistance to obinutuzumab-induced antibody-dependent cellular cytotoxicity caused by abnormal Fas signaling is overcome by combination therapies.

BACKGROUND: Obinutuzumab, a Type II anti-CD20 antibody, is used to treat follicular lymphoma. A major mode of action of obinutuzumab is antibody-dependent cellular cytotoxicity (ADCC). Knowledge of the mechanisms of resistance to obinutuzumab is important for the development of next-line strategies to follow obinutuzumab-containing therapy, including obinutuzumab retreatment. Unfortunately, the mechanisms by which tumor cells acquire resistance to ADCC are still poorly understood. To address this, we examined the mechanisms of resistance to obinutuzumab-induced ADCC and the combination efficacy of obinutuzumab and clinically available agents in the established resistant cells. METHODS AND RESULTS: We established cells resistant to obinutuzumab-induced ADCC using the non-Hodgkin lymphoma cell line RL and examined their mechanisms of resistance and the combination efficacy of obinutuzumab and clinically available agents. Comprehensive analysis by RNA sequencing of resistance mechanisms revealed that abnormal Fas signaling decreased sensitivity to ADCC in resistant clones. Combination treatment with prednisolone, a component of CHOP and CVP, was found to enhance ADCC sensitivity of RL cells and resistant clones and to significantly suppress tumor growth in xenograft models. Treatment with prednisolone upregulated expression of CD20 and an apoptosis-inducing protein BIM, which might augment perforin/granzyme B-mediated cell death. Furthermore, pretreatment of the effector cells with bendamustine enhanced ADCC activity, and treatment with obinutuzumab plus bendamustine showed significant antitumor efficacy in xenograft models. It was speculated that bendamustine upregulates ADCC activity by potentiating granules-mediated cell killing. CONCLUSIONS: Our study revealed a novel mechanism underlying obinutuzumab-induced ADCC resistance and indicated that ADCC resistance could be overcome by combining obinutuzumab with prednisolone or bendamustine. This study provides a scientific rationale for obinutuzumab-retreatment in combination with clinically available chemotherapeutic agents for obinutuzumab resistant follicular lymphoma.

Anti­VEGF antibody triggers the effect of anti­PD­L1 antibody in PD­L1low and immune desert­like mouse tumors.

The efficacy of programmed cell death­ligand 1 (PD­L1)/programmed cell death protein 1 (PD­1) blockade therapy has been demonstrated but is limited in patients with PD­L1low or immune desert tumors. This limitation can be overcome by combination therapies that include anti­vascular endothelial growth factor (VEGF) therapy. Such combinations have been investigated in clinical trials for a number of cancer types; however, evidence on the mechanisms underlying their effects in these types of patients is still not sufficient. Therefore, the present study investigated the efficacy and effects on CD8+ T cell and C­X­C motif chemokine receptor 3 (CXCR3) ligand expression in tumors by combining anti­PD­L1 and anti­VEGF antibodies using an OV2944­HM­1 mouse model with PD­L1low and immune desert­like phenotypes. Although the model exhibited anti­PD­L1 insensitivity, anti­PD­L1 antibody treatment combined with anti­VEGF antibody inhibited tumor growth compared with anti­VEGF monotherapy, which itself inhibited tumor growth compared with the control treatment on Day 25. In combination­treated mice, a higher percentage of CD8+ T cells and higher levels of CXCR3 ligands were observed in tumor tissues compared with those in the anti­VEGF antibody treatment group, which was not significantly different from control treatment on Day 8. The increase in the intratumoral percentage of CD8+ T cells following the combination treatment was reversed by CXCR3 blocking to the same level as the control. In an anti­PD­L1 insensitive model with PD­L1low and immune desert­like phenotypes, although anti­PD­L1 antibody alone was not effective, anti­PD­L1 antibody in combination with anti­VEGF antibody exhibited antitumor combination efficacy with an increase of CD8+ T cell infiltration, which was suggested to be dependent on the increase of intratumoral CXCR3 ligands. This mechanism could explain the efficacy of anti­PD­L1 antibody and anti­VEGF antibody combination therapy in the clinical setting.

PD-L1 blockade exhibits anti-tumor effect on brain metastasis by activating CD8+ T cells in hematogenous metastasis model with lymphocyte infusion.

Brain metastases are common complication in cancer patients. Immune checkpoint inhibitors show therapeutic benefits also in patients with central nervous system (CNS) metastases. However, their antitumor effects on metastatic tumors and their underlying mechanisms are still poorly understood. In this study we investigated the antitumor effect of anti-programmed death-ligand 1 (PD-L1) antibody on metastatic brain tumors and evaluated immune responses during treatment. We employed a hematogenous brain metastasis xenograft model using immunodeficient mice with murine lymphocyte infusions. A human non-small-cell lung cancer (NSCLC) cell line stably expressing NanoLuc® reporter (Nluc-H1915) was inoculated from the internal carotid artery of SCID mice. After metastases were established (24 days after inoculation), splenocytes prepared from H1915-immunized BALB/c mice were injected intravenously and mouse IgG or anti-PD-L1 antibody treatment was started (day 1). Evaluated by Nluc activity, tumor volume in the brain on day 14 was significantly lower in anti-PD-L1-treated mice than in mouse IgG-treated mice. Furthermore CD8+ cells were primarily infiltrated intratumorally and peritumorally and anti-PD-L1 treatment induced a significantly higher proportion of Granzyme B (GzmB)+ cells among CD8+ T cells. The antitumor effect of anti-PD-L1 antibody on brain metastasis is thought to be achieved by the enhanced activation of infiltrated CD8+ T cells into metastatic brain tumor. These results suggest that anti-PD-L1 antibody-containing regimens may be promising treatment options for cancer patients with brain metastases.

B7-1 and programmed cell death-ligand 1 in primary and lymph node metastasis lesions of non-small cell lung carcinoma.

BACKGROUND: Programmed cell death ligand 1 (PD-L1) status has been reported to be different between metastatic and primary lesions in some cases. Therefore, the interaction between carcinoma and immune cells could influence their expression in the tumor microenvironment. PD-L1 is known to bind not only to Programmed cell death 1 (PD-1) but also to B7-1 (CD80). In this study, we examined the interaction between lung carcinoma cell lines and peripheral blood mononuclear cells (PBMCs) in vitro. We then examined the significance of B7-1 expression non-small cell lung cancer (NSCLC) microenvironment. METHODS: The interaction of lung carcinoma cell lines and PBMC through the soluble factors was analyzed using a co-culture system. The changes in expression of immune checkpoint-related factors in PBMC were examined by PD-1/PD-L1 Checkpoint Pathway qPCR Array Kit. B7-1 expression in NSCLC tissues was examined by immunohistochemistry. RESULTS: B7-1 was upregulated following the co-culture with the lung carcinoma cell lines. B7-1 expression in NSCLC tissues was significantly higher in smokers and squamous cell carcinomas and was significantly positively correlated with PD-L1 status in primary cancer. However, B7-1 and PD-1 were not correlated between primary and metastatic diseases in the same patients. CONCLUSION: PD-1 inhibitors inhibited PD-1/PD-L1 binding but not PD-L1/B7-1 binding. These results demonstrated that the intratumoral ratio of B7-1 positive T cells in NSCLC tissue could be involved in the therapeutic efficacy of PD-L1 inhibitors. This study focused on lymph node metastasis but other sites of distant metastases should be explored by further analysis.

Anti-VEGF Antibody Protects against Alveolar Exudate Leakage Caused by Vascular Hyperpermeability, Resulting in Mitigation of Pneumonitis Induced by Immunotherapy.

Immune-related pneumonitis is an important toxicity associated with checkpoint inhibitor therapy with anti-PD-1 or anti-PD-L1 antibodies, often necessitating discontinuation of treatment. Development of methods to mitigate checkpoint inhibitor-related pneumonitis is required.The contributions of PD-L1, PD-L2, and VEGF to the pathogenesis of pneumonitis were examined in an IL2- plus IL18-induced mouse pneumonitis model (IL pneumonitis model). Furthermore, the incidences of pneumonitis were retrospectively examined in patients with non-small cell lung cancer treated with the anti-PD-L1 mAb atezolizumab plus chemotherapy, with or without the anti-VEGF mAb bevacizumab, in the phase III IMpower150 trial. PD-1 signal blockade by anti-PD-L1 and anti-PD-L2 antibodies aggravated pneumonitis in the IL pneumonitis model. An anti-VEGF antibody prevented PD-1 signal blockade from aggravating pneumonitis in this model. PD-1 signal blockade induced interstitial T-cell infiltration in the lungs, but VEGF blockade did not affect this T-cell infiltration. The anti-VEGF antibody protected against vascular-to-alveolar leakage of protein and fluid due to PD-1 signal blockade in a murine model. In the IMpower150 trial, incidence rates of pneumonitis of any grade were 4.3% in the group without bevacizumab and 2.8% in the group with bevacizumab. In patients with pneumonitis, outcomes of "Not recovered/Not resolved" were reported for 29.4% in the group without bevacizumab compared with 9.1% in the group with bevacizumab. Our findings suggest that anti-VEGF antibodies in combination with checkpoint inhibitors may be a treatment method that can control checkpoint inhibitor-related pneumonitis.

Both T cell priming in lymph node and CXCR3-dependent migration are the key events for predicting the response of atezolizumab.

Anti-PD-L1 antibodies benefit many cancer patients, even those with "non-inflamed tumor". Determining which patients will benefit remains an important clinical goal. In a non-inflamed tumor mouse model, we found that PD-L1 was highly expressed on antigen-presenting cells (APCs) especially on CD103+ CD11c+ dendritic cells in tumor-draining lymph nodes (dLNs), suppressing T-cell priming by APCs. In this model, anti-PD-L1 antibodies enhanced T-cell priming and increased CXCR3+ activated T-cells in dLNs, which was followed by the trafficking of T-cells to tumors in response to CXCR3 ligands. As predictive biomarker, each APCs-related gene expression (AP score) alone or T-cells trafficking-related chemokine gene expression (T score) alone were still less than perfect among the 17 mouse models examined. However a combining score of AP score and T score (AP/T score) precisely identified anti-PD-L1-sensitive tumors. In the phase 3 trial of atezolizumab vs docetaxel in advanced NSCLC patients (OAK), the AP/T score could identify atezolizumab-treated NSCLC patients who achieved significant improvement in overall survival. This biomarker concept would be a clinically valuable for prediction of anti-PD-L1 antibody efficacy.

Blockade of PD-1/PD-L1 Pathway Enhances the Antigen-Presenting Capacity of Fibrocytes.

Fibrocytes, a distinct population of collagen-producing, monocyte-derived cells, are involved in wound healing as well as fibrotic diseases. Recently, fibrocytes have been revealed to play a role in the tumor microenvironment, particularly under antiangiogenic therapy. In addition, combination cancer immunotherapy with immune checkpoint inhibitor and antiangiogenic agents have been developed for various cancers in the clinical setting, although the immunological background is not clear. In the current study, we aimed to determine the function of fibrocytes in tumor immunity induced by immune checkpoint inhibitor therapy. Human and murine fibrocytes were generated from PBMCs and lungs, respectively. The expression of costimulatory and inhibitory molecules on fibrocytes was examined by flow cytometry. The stimulation of CD8+ T cells by fibrocytes was examined in MLRs with a 3H-thymidine incorporation assay. Fibrocytes expressed CD80low and CD86high as a costimulatory molecule, and expressed PD-L1high, but not PD-L2, as a coinhibitory molecule. Without any stimulation, fibrocytes strongly enhanced the proliferation of CD8+ T cells in mice and humans. Treatment with anti-CD86 and -CD54 Abs inhibited the growth of CD8+ T cells induced by fibrocytes. Anti-PD-L1 Ab further enhanced the proliferation of CD8+ T cells, even in the OVA-specific MLR with OT-1Rag-/- mice. Importantly, fibrocytes derived from PBMCs of patients with lung adenocarcinoma or murine MC38 tumors augmented the proliferation of CD8+ T cells with PD-L1 blockade. These results suggest that fibrocytes infiltrating tumor sites may play a role in the antitumor immunity mediated by CD8+ T cells when the activity is further enhanced by PD-L1/PD-1 blockade.

Bevacizumab suppresses the growth of established non-small-cell lung cancer brain metastases in a hematogenous brain metastasis model.

Brain metastases are common in patients with non-small-cell lung cancer (NSCLC). The efficacy of bevacizumab, an anti-vascular endothelial growth factor (VEGF) humanized antibody, has been demonstrated in patients with nonsquamous NSCLC. We established a transplantable NSCLC cell line (Nluc-H1915) that stably expresses NanoLuc® reporter and confirmed the correlation between total Nluc activity in tumor and tumor volume in vivo. SCID mice inoculated with these cells through the internal carotid artery formed reproducible brain metastases, in which human VEGF was detected. Next, after metastases were established in the model mice (15-17 days), they were intraperitoneally administered weekly doses of human immunoglobulin G (HuIgG) or bevacizumab. Nluc activity in the brain was significantly lower in bevacizumab-treated mice than in HuIgG-treated mice. Additionally, bevacizumab concentration in the brain was higher in mice with brain metastasis than in normal mice, and bevacizumab was primarily observed in brain metastasis lesions. The microvessel density in brain metastasis was lower in bevacizumab-treated mice than in HuIgG-treated mice. We believe bevacizumab's anti-proliferative effect on brain metastasis is due to anti-angiogenic activity achieved by its penetration into brain metastases; this suggests that a bevacizumab-containing regimen may be a promising treatment option for patients with NSCLC brain metastasis.

Alectinib shows potent antitumor activity against RET-rearranged non-small cell lung cancer.

Alectinib/CH5424802 is a known inhibitor of anaplastic lymphoma kinase (ALK) and is being evaluated in clinical trials for the treatment of ALK fusion-positive non-small cell lung cancer (NSCLC). Recently, some RET and ROS1 fusion genes have been implicated as driver oncogenes in NSCLC and have become molecular targets for antitumor agents. This study aims to explore additional target indications of alectinib by testing its ability to inhibit the activity of kinases other than ALK. We newly verified that alectinib inhibited RET kinase activity and the growth of RET fusion-positive cells by suppressing RET phosphorylation. In contrast, alectinib hardly inhibited ROS1 kinase activity unlike other ALK/ROS1 inhibitors such as crizotinib and LDK378. It also showed antitumor activity in mouse models of tumors driven by the RET fusion. In addition, alectinib showed kinase inhibitory activity against RET gatekeeper mutations (RET V804L and V804M) and blocked cell growth driven by the KIF5B-RET V804L and V804M. Our results suggest that alectinib is effective against RET fusion-positive tumors. Thus, alectinib might be a therapeutic option for patients with RET fusion-positive NSCLC.

Antitumor activity of the selective ALK inhibitor alectinib in models of intracranial metastases.

PURPOSE: The clinical efficacy of the anaplastic lymphoma kinase (ALK) inhibitor crizotinib has been demonstrated in ALK fusion-positive non-small cell lung cancer (NSCLC); however, brain metastases are frequent sites of initial failure in patients due to poor penetration of the central nervous system by crizotinib. Here, we examined the efficacy of a selective ALK inhibitor alectinib/CH5424802 in preclinical models of intracranial tumors. METHODS: We established intracranial tumor implantation mouse models of EML4-ALK-positive NSCLC NCI-H2228 and examined the antitumor activity of alectinib in this model. Plasma distribution and brain distribution of alectinib were examined by quantitative whole-body autoradiography administrating a single oral dose of (14)C-labeled alectinib to rats. The drug permeability of alectinib was evaluated in Caco-2 cell. RESULTS: Alectinib resulted in regression of NCI-H2228 tumor in mouse brain and provided a survival benefit. In a pharmacokinetic study using rats, alectinib showed a high brain-to-plasma ratio, and in an in vitro drug permeability study using Caco-2 cells, alectinib was not transported by P-glycoprotein efflux transporter that is a key factor in blood-brain barrier penetration. CONCLUSIONS: We established intracranial tumor implantation models of EML4-ALK-positive NSCLC. Alectinib showed potent efficacy against intracranial EML4-ALK-positive tumor. These results demonstrated that alectinib might provide therapeutic opportunities for crizotinib-treated patients with brain metastases.

Selective ALK inhibitor alectinib with potent antitumor activity in models of crizotinib resistance.

The clinical efficacy of the ALK inhibitor crizotinib has been demonstrated in ALK fusion-positive NSCLC; however, resistance to crizotinib certainly occurs through ALK secondary mutations in clinical use. Here we examined the efficacy of a selective ALK inhibitor alectinib/CH5424802 in models of crizotinib resistance. Alectinib led to tumor size reduction in EML4-ALK-positive xenograft tumors that failed to regress fully during the treatment with crizotinib. In addition, alectinib inhibited the growth of some EML4-ALK mutant-driven tumors, including the G1269A model. These results demonstrated that alectinib might provide therapeutic opportunities for crizotinib-treated patients with ALK secondary mutations.

Enhanced antitumor activity of erlotinib in combination with the Hsp90 inhibitor CH5164840 against non-small-cell lung cancer.

Inhibition of heat shock protein 90 (Hsp90) can lead to degradation of multiple client proteins, which are involved in tumor progression. Epidermal growth factor receptor (EGFR) is one of the most potent oncogenic client proteins of Hsp90. Targeted inhibition of EGFR has shown clinical efficacy in the treatment of patients with non-small-cell lung cancer (NSCLC). However, primary and acquired resistance to the existing EGFR inhibitors is a major clinical problem. In the present study, we investigated the effect of the novel Hsp90 inhibitor CH5164840 on the antitumor activity of erlotinib. The NSCLC cell lines and xenograft models were treated with CH5164840 and erlotinib to examine their mechanisms of action and cell growth inhibition. We found that CH5164840 showed remarkable antitumor activity against NSCLC cell lines and xenograft models. The addition of CH5164840 enhanced the antitumor activity of erlotinib against NCI-H292 EGFR-overexpressing xenograft models. Phosphorylation of Stat3 increased with erlotinib treatment in NCI-H292 cells, which was abrogated by Hsp90 inhibition. Furthermore, in a NCI-H1975 T790M mutation erlotinib-resistant model, CH5164840 enhanced the antitumor activity of erlotinib despite the low efficacy of erlotinib treatment alone. In addition, ERK signaling was effectively suppressed by combination treatment with erlotinib and CH5164840 in a NCI-H1975 erlotinib-resistant model. Taken together, these data indicate that CH5164840 has potent antitumor activity and is highly effective in combination with erlotinib against NSCLC tumors with EGFR overexpression and mutations. Our results support the therapeutic potential of CH5164840 as a Hsp90 inhibitor for combination therapy with EGFR-targeting agents against EGFR-addicted NSCLC.

Preclinical antitumor activity of the novel heat shock protein 90 inhibitor CH5164840 against human epidermal growth factor receptor 2 (HER2)-overexpressing cancers.

Heat shock protein 90 (Hsp90), a molecular chaperone that plays a significant role in the stability and maturation of client proteins, including oncogenic targets for cell transformation, proliferation, and survival, is an attractive target for cancer therapy. We identified the novel Hsp90 inhibitor, CH5164840, and investigated its induction of oncogenic client protein degradation, antiproliferative activity, and apoptosis against an NCI-N87 gastric cancer cell line and a BT-474 breast cancer cell line. Interestingly, CH5164840 demonstrated tumor selectivity both in vitro and in vivo, binding to tumor Hsp90 (which forms active multiple chaperone complexes) in vitro, and being distributed effectively to tumors in a mouse model, which, taken together, supports the decreased levels of phosphorylated Akt by CH5164840 that we observed in tumor tissues, but not in normal tissues. As well as being well tolerated, the oral administration of CH5164840 exhibited potent antitumor efficacy with regression in NCI-N87 and BT-474 tumor xenograft models. In addition, CH5164840 significantly enhanced antitumor efficacy against gastric and breast cancer models when combined with the human epidermal growth factor receptor 2 (HER2)-targeted agents, trastuzumab and lapatinib. These data demonstrate the potent antitumor efficacy of CH5164840 when administered alone, and its significant combination efficacy when combined with trastuzumab or lapatinib, supporting the clinical development of CH5164840 as an Hsp90 inhibitor for combination therapy with HER2-targeted agents against HER2-overexpressing tumors.

The selective class I PI3K inhibitor CH5132799 targets human cancers harboring oncogenic PIK3CA mutations.

PURPOSE: The phosphatidylinositol 3-kinase (PI3K) pathway plays a central role in cell proliferation and survival in human cancer. PIK3CA mutations, which are found in many cancer patients, activate the PI3K pathway, resulting in cancer development and progression. We previously identified CH5132799 as a novel PI3K inhibitor. Thus, this study aimed to clarify the biochemical and antitumor activity of CH5132799 and elucidate the correlation between CH5132799 response and genetic alterations in the PI3K pathway. EXPERIMENTAL DESIGN: Kinase inhibitory activity was profiled in cell-free assays. A large panel of human breast, ovarian, prostate, and endometrial cancer cell lines, as well as xenograft models, were used to evaluate the antitumor activity of CH5132799, followed by analysis for genetic alterations. Effects on Akt phosphorylation induced by mTORC1 inhibition were tested with CH5132799 and compared with mTORC1 and PI3K/mTOR inhibitors. RESULTS: CH5132799 selectively inhibited class I PI3Ks and PI3Kα mutants in in vitro kinase assays. Tumors harboring PIK3CA mutations were significantly sensitive to CH5132799 in vitro and were remarkably regressed by CH5132799 in in vivo mouse xenograft models. In combination with trastuzumab, tumors disappeared in the trastuzumab-insensitive breast cancer model with the PIK3CA mutation. Moreover, CH5132799 did not reverse a negative feedback loop of PI3K/Akt/mTOR signaling and induced regression against tumors regrown after long-term mTORC1 inhibitor treatment. CONCLUSIONS: CH5132799 is a selective class I PI3K inhibitor with potent antitumor activity against tumors harboring the PIK3CA mutations. Prediction of CH5132799 response on the basis of PIK3CA mutations could enable patient stratification in clinical settings.

Discovery and biological activity of a novel class I PI3K inhibitor, CH5132799.

Phosphatidylinositol 3-kinase (PI3K) is a lipid kinase and a promising therapeutic target for cancer. Using structure-based drug design (SBDD), we have identified novel PI3K inhibitors with a dihydropyrrolopyrimidine skeleton. Metabolic stability of the first lead series was drastically improved by replacing phenol with aminopyrimidine moiety. CH5132799, a novel class I PI3K inhibitor, exhibited a strong inhibitory activity especially against PI3Kα (IC(50)=0.014 µM). In human tumor cell lines with PI3K pathway activation, CH5132799 showed potent antiproliferative activity. CH5132799 is orally available and showed significant antitumor activity in PI3K pathway-activated human cancer xenograft models in mice.

Phosphoproteomic analysis of distinct tumor cell lines in response to nocodazole treatment.

Here, we report for the first time a comparative phosphoproteomic analysis of distinct tumor cell lines in the presence or absence of the microtubule-interfering agent nocodazole. In total, 1525 phosphorylation sites assigned to 726 phosphoproteins were identified using LC-MS-based technology following phosphopeptide enrichment. Analysis of the amino acid composition surrounding the identified in vivo phosphorylation sites revealed that they could be classified into two motif groups: pSer-Pro and pSer-Asp/Glu. Phosphoproteomic change resulting from nocodazole treatment varied among cell lines in terms of the numbers of total phosphopeptides identified, motif groups, and functional annotation groups; however, the cell lines were equally sensitive to nocodazole. The identified phosphoproteome subset contained major signaling proteins and proteins known to be involved in mitosis, but did not always exhibit the same changes in the tumor cells from nocodazole treatment. In spite of the complex changes observed in the phosphorylation of many of the proteins, possible common features induced by nocodazole were found, including phosphorylation of nucleophosmin (NPM) S254 and coatomer protein complex, subunit alpha (COPA) S173, suggesting that the events are not cell-type specific but events generally occurring in mitosis or induced by a microtubule-interfering agent. Further, temporal analysis of phosphoproteome change revealed that phosphorylation of NPM S254 and COPA S173 was observed from the early (6 h) and late (24 h) time point after nocodazole treatment, respectively, suggesting that NPM S254 may be involved in the induction of M-phase arrest by nocodazole, whereas COPA S173 may be caused as a result of M-phase arrest.

Synthesis and structure-activity relationships of novel benzofuran farnesyltransferase inhibitors.

A series of benzofuran-based farnesyltransferase inhibitors have been designed and synthesized as antitumor agents. Among them, 11f showed the most potent enzyme inhibitory activity (IC(50)=1.1nM) and antitumor activity in human cancer xenografts in mice.