A phase II study of enzastaurin in combination with erlotinib in patients with previously treated advanced non-small cell lung cancer

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Tumor-associated macrophages mediate resistance of EGFR-TKIs in non-small cell lung cancer: mechanisms and prospects

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the first-line standard treatment for advanced non-small cell lung cancer (NSCLC) with EGFR mutation. However, resistance to EGFR-TKIs is inevitable. Currently, most studies on the mechanism of EGFR-TKIs resistance mainly focus on the spontaneous resistance phenotype of NSCLC cells. Studies have shown that the tumor microenvironment (TME) also mediates EGFR-TKIs resistance in NSCLC. Tumor-associated macrophages (TAMs), one of the central immune cells in the TME of NSCLC, play an essential role in mediating EGFR-TKIs resistance. This study aims to comprehensively review the current mechanisms underlying TAM-mediated resistance to EGFR-TKIs and discuss the potential efficacy of combining EGFR-TKIs with targeted TAMs therapy. Combining EGFR-TKIs with TAMs targeting may improve the prognosis of NSCLC with EGFR mutation to some extent.

Protein Kinase C at the Crossroad of Mutations, Cancer, Targeted Therapy and Immune Response

The frequent PKC dysregulations observed in many tumors have made these enzymes natural targets for anticancer applications. Nevertheless, this considerable interest in the development of PKC modulators has not led to the expected therapeutic benefits, likely due to the complex biological activities regulated by PKC isoenzymes, often playing ambiguous and protective functions, further driven by the occurrence of mutations. The structure, regulation and functions of PKCs have been extensively covered in other publications. Herein, we focused on PKC alterations mostly associated with complete functional loss. We also addressed the modest yet encouraging results obtained targeting PKC in selected malignancies and the more frequent negative clinical outcomes. The reported observations advocate the need for more selective molecules and a better understanding of the involved pathways. Furthermore, we underlined the most relevant immune mechanisms controlled by PKC isoforms potentially impacting the immune checkpoint inhibitor blockade-mediated immune recovery. We believe that a comprehensive examination of the molecular features of the tumor microenvironment might improve clinical outcomes by tailoring PKC modulation. This approach can be further supported by the identification of potential response biomarkers, which may indicate patients who may benefit from the manipulation of distinctive PKC isoforms.

Activators and Inhibitors of Protein Kinase C (PKC): Their Applications in Clinical Trials

Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinase, is classed into three subfamilies based on their structural and activation characteristics: conventional or classic PKC isozymes (cPKCs; α, βI, βII, and γ), novel or non-classic PKC isozymes (nPKCs; δ, ε, η, and θ), and atypical PKC isozymes (aPKCs; ζ, ι, and λ). PKC inhibitors and activators are used to understand PKC-mediated intracellular signaling pathways and for the diagnosis and treatment of various PKC-associated diseases, such as cancers, neurological diseases, cardiovascular diseases, and infections. Many clinical trials of PKC inhibitors in cancers showed no significant clinical benefits, meaning that there is a limitation to design a cancer therapeutic strategy targeting PKC alone. This review will focus on the activators and inhibitors of PKC and their applications in clinical trials.

Erlotinib-based targeted dual agent versus erlotinib alone in previously treated advanced non-small-cell lung cancer: a meta-analysis of 13 randomized controlled trials

OBJECTIVES

To compare the effects of an erlotinib-based targeted dual agent with erlotinib alone in previously treated patients with advanced non-small lung cancer (NSCLC).

PATIENTS AND METHODS

The PubMed and Embase databases and the Cochrane Central Register of Controlled Trials were searched for publications between January 2005 and March 2016. Hazard ratios (HRs) with their 95% confidence intervals (CIs), or data for calculating HRs with 95% CIs were derived. Overall survival (OS), progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), and toxicity were assessed.

RESULTS

Thirteen trials with a total of 4509 patients were included in this meta-analysis. Compared with erlotinib alone, combination therapy showed no improvement in OS (HR = 0.95; 95% CI, 0.89-1.02; P = .132) though significantly prolonged PFS (HR = 0.82; 95% CI, 0.75-0.90; P < .001). Combination therapy significantly increased ORR (RR = 1.32; 95% CI, 1.09-1.60; P = .005) and DCR (RR = 1.26; 95% CI, 1.17-1.36, P < .001). Sub-analysis assessment failed to identify any sub-groups which could benefit from combination therapy in terms of OS. Combination therapy was associated with more grade 3 or higher toxic effects (RR = 1.54; 95% CI, 1.22-1.95; P < .001). Patients treated with combination therapy had more grade 3 or greater fatigue (RR = 1.49; 95% CI, 1.16-1.91; P = .002), but did not develop more diarrhea (RR = 2.02; 95% CI, 0.86-4.77; P = .107) or rash (RR = 1.29, 95% CI, 0.90-1.85; P = .172). This study had limitations about heterogeneities among the included trials, and the analysis was not based on individual patient data.

CONCLUSIONS

Compared with erlotinib alone, the erlotinib-based targeted dual agent showed a minimal magnitude of improvement in PFS but did not improve OS. The role of erlotinib-based combinations in previously treated patients with NSCLC seemed insignificant.

Zinc finger MYND-type containing 8 promotes tumour angiogenesis via induction of vascular endothelial growth factor-A expression

Zinc finger, MYND-type containing 8 (ZMYND8) encodes a receptor for activated C-kinase protein. Here, we report that ZMYND8 promotes angiogenesis in prostate cancer xenografts in zebrafish, as well as tube formation in human umbilical vascular endothelial cell (HUVEC) cultures. Using transcriptome analyses, we found upregulation of ZMYND8 expression in both zebrafish prostate cancer xenografts and prostate cancer samples from patients. In vitro and in vivo ZMYND8 knockdown suppressed angiogenesis, whereas ZMYND8 overexpression enhanced angiogenesis. Notably, ZMYND8 induced vegfa mRNA expression selectively in prostate cancer xenografts. Integrated analysis of human and zebrafish transcriptomes, which identified ZMYND8, might be a powerful strategy to determine also other molecular targets for inhibiting prostate cancer progression.

Non-Small Cell Lung Cancer beyond Biomarkers: The Evolving Landscape of Clinical Trial Design

The approval of EGFR and ALK directed tyrosine kinase inhibitors materialized the concept of tailoring therapy on the basis of specific biomarkers for treating patients with NSCLC. Research for other biologics, although demonstrating clinical benefit, has been less successful so far for producing biomarkers that predict response. Blocking angiogenesis is the prototype for the agents that belong in the latter group that target specific molecules, yet they are currently approved for relatively unselected groups of patients. In order to meet the goal of personalizing care in the various settings of NSCLC, a wealth of biologics and compounds are currently being tested in clinical trials in different phases of clinical development. In a subset of the relevant studies, a biomarker perspective is appreciated. This review summarizes the clinical rationale of the major ongoing phase II and III NSCLC studies that employ targeting specific molecules with novel agents, as well as innovative strategies, and includes a comparative discussion of the different designs.

Combined PKC and MEK inhibition in uveal melanoma with GNAQ and GNA11 mutations

Uveal melanoma (UM) is a genetically and biologically distinct type of melanoma, and once metastatic there is no effective treatment currently available. Eighty percent of UMs harbor mutations in the Gαq family members GNAQ and GNA11. Understanding the effector pathways downstream of these oncoproteins is important to identify opportunities for targeted therapy. We report consistent activation of the protein kinase C (PKC) and MAPK pathways as a consequence of GNAQ or GNA11 mutation. PKC inhibition with AEB071 or AHT956 suppressed PKC and MAPK signalling and induced G1 arrest selectively in melanoma cell lines carrying GNAQ or GNA11 mutations. In contrast, treatment with two different MEK inhibitors, PD0325901 and MEK162, inhibited the proliferation of melanoma cell lines irrespective of their mutation status, indicating that in the context of GNAQ or GNA11 mutation MAPK activation can be attributed to activated PKC. AEB071 significantly slowed the growth of tumors in an allograft model of GNAQ(Q209L)-transduced melanocytes, but did not induce tumor shrinkage. In vivo and in vitro studies showed that PKC inhibitors alone were unable to induce sustained suppression of MAP-kinase signaling. However, combinations of PKC and MEK inhibition, using either PD0325901or MEK162, led to sustained MAP-kinase pathway inhibition and showed a strong synergistic effect in halting proliferation and in inducing apoptosis in vitro. Furthermore, combining PKC and MEK inhibition was efficacious in vivo, causing marked tumor regression in a UM xenograft model. Our data identify PKC as a rational therapeutic target for melanoma patients with GNAQ or GNA11 mutations and demonstrate that combined MEK and PKC inhibition is synergistic, with superior efficacy compared to treatment with either approach alone.

Novel small molecule EGFR inhibitors as candidate drugs in non-small cell lung cancer

In the last decade, better understanding of the role of epidermal growth factor receptor in the pathogenesis and progression of non-small cell lung cancer has led to a revolution in the work-up of these neoplasms. Tyrosine kinase inhibitors, such as erlotinib and gefitinib, have been approved for the treatment of non-small cell lung cancer, demonstrating an improvement in progression-free and overall survival, particularly in patients harboring activating EGFR mutations. Nevertheless, despite initial responses and long-lasting remissions, resistance to tyrosine kinase inhibitors invariably develops, most commonly due to the emergence of secondary T790M mutations or to the amplification of mesenchymal-epithelial transition factor (c-Met), which inevitably leads to treatment failure. Several clinical studies are ongoing (http://www.clinicaltrials.gov), aimed to evaluate the efficacy and toxicity of combined approaches and to develop novel irreversible or multitargeted tyrosine kinase inhibitors and mutant-selective inhibitors to overcome such resistance. This review is an overview of ongoing Phase I, II, and III trials of novel small molecule epidermal growth factor receptor inhibitors and combinations in non-small cell lung cancer patients.

Erlotinib resistance in lung cancer: current progress and future perspectives

Lung cancer is the most common cancer in the world. Despite modern advancements in surgeries, chemotherapies, and radiotherapies over the past few years, lung cancer still remains a very difficult disease to treat. This has left the death rate from lung cancer victims largely unchanged throughout the past few decades. A key cause for the high mortality rate is the drug resistance that builds up for patients being currently treated with the chemotherapeutic agents. Although certain chemotherapeutic agents may initially effectively treat lung cancer patients, there is a high probability that there will be a reoccurrence of the cancer after the patient develops resistance to the drug. Erlotinib, the epidermal growth factor receptor (EGFR)-targeting tyrosine kinase inhibitor, has been approved for localized as well as metastatic non-small cell lung cancer where it seems to be more effective in patients with EGFR mutations. Resistance to erlotinib is a common observation in clinics and this review details our current knowledge on the subject. We discuss the causes of such resistance as well as innovative research to overcome it. Evidently, new chemotherapy strategies are desperately needed in order to better treat lung cancer patients. Current research is investigating alternative treatment plans to enhance the chemotherapy that is already offered. Better insight into the molecular mechanisms behind combination therapy pathways and even single molecular pathways may help improve the efficacy of the current treatment options.