Phase I study of temsirolimus in combination with cetuximab in patients with advanced solid tumours

Prospects of targeting PI3K/AKT/mTOR pathway in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has one of the worst prognoses among all malignancies. PI3K/AKT/mTOR signaling pathway, a main downstream effector of KRAS is involved in the regulation of key hallmarks of cancer. We here report that whole-genome analyses demonstrate the frequent involvement of aberrant activations of PI3K/AKT/mTOR pathway components in PDAC patients and critically evaluate preclinical and clinical evidence on the application of PI3K/AKT/mTOR pathway targeting agents. Combinations of these agents with chemotherapeutics or other targeted therapies, including the modulators of cyclin-dependent kinases, receptor tyrosine kinases and RAF/MEK/ERK pathway are also examined. Although human genetic studies and preclinical pharmacological investigations have provided strong evidence on the role of PI3K/AKT/mTOR pathway in PDAC, clinical studies in general have not been as promising. Patient stratification seems to be the key missing point and with the advent of biomarker-guided clinical trials, targeting PI3K/AKT/mTOR pathway could provide valuable assets for treatment of pancreatic cancer patients.

Integrated Transcriptome Profiling Identifies Prognostic Hub Genes as Therapeutic Targets of Glioblastoma: Evidenced by Bioinformatics Analysis

Glioblastoma (GBM) is the most devastating and frequent type of primary brain tumor with high morbidity and mortality. Despite the use of surgical resection followed by radio- and chemotherapy as standard therapy, the progression of GBM remains dismal with a median overall survival of <15 months. GBM embodies a populace of cancer stem cells (GSCs) that is associated with tumor initiation, invasion, therapeutic resistance, and post-treatment reoccurrence. However, understanding the potential mechanisms of stemness and their candidate biomarkers remains limited. Hence in this investigation, we aimed to illuminate potential candidate hub genes and key pathways associated with the pathogenesis of GSC in the development of GBM. The integrated analysis discovered differentially expressed genes (DEGs) between the brain cancer tissues (GBM and GSC) and normal brain tissues. Multiple approaches, including gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, were employed to functionally annotate the DEGs and visualize them through the R program. The significant hub genes were identified through the protein-protein interaction network, Venn diagram analysis, and survival analysis. We observed that the upregulated DEGs were prominently involved in the ECM-receptor interaction pathway. The downregulated genes were mainly associated with the axon guidance pathway. Five significant hub genes (CTNNB1, ITGB1, TNC, EGFR, and SHOX2) were screened out through multiple analyses. GO and KEGG analyses of hub genes uncovered that these genes were primarily enriched in disease-associated pathways such as the inhibition of apoptosis and the DNA damage repair mechanism, activation of the cell cycle, EMT (epithelial-mesenchymal transition), hormone AR (androgen receptor), hormone ER (estrogen receptor), PI3K/AKT (phosphatidylinositol 3-kinase and AKT), RTK (receptor tyrosine kinase), and TSC/mTOR (tuberous sclerosis complex and mammalian target of rapamycin). Consequently, the epigenetic regulatory network disclosed that hub genes played a vital role in the progression of GBM. Finally, candidate drugs were predicted that can be used as possible drugs to treat GBM patients. Overall, our investigation offered five hub genes (CTNNB1, ITGB1, TNC, EGFR, and SHOX2) that could be used as precise diagnostic and prognostic candidate biomarkers of GBM and might be used as personalized therapeutic targets to obstruct gliomagenesis.

Recent insights in the PI3K/Akt pathway as a promising therapeutic target in combination with EGFR-targeting agents to treat head and neck squamous cell carcinoma

Resistance to therapies targeting the epidermal growth factor receptor (EGFR), such as cetuximab, remains a major roadblock in the search for effective therapeutic strategies in head and neck squamous cell carcinoma (HNSCC). Due to its close interaction with the EGFR pathway, redundant or compensatory activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway has been proposed as a major driver of resistance to EGFR inhibitors. Understanding the role of each of the main proteins involved in this pathway is utterly important to develop rational combination strategies able to circumvent resistance. Therefore, the current work reviewed the role of PI3K/Akt pathway proteins, including Ras, PI3K, tumor suppressor phosphatase and tensing homolog, Akt and mammalian target of rapamycin in resistance to anti-EGFR treatment in HNSCC. In addition, we summarize PI3K/Akt pathway inhibitors that are currently under (pre)clinical investigation with focus on overcoming resistance to EGFR inhibitors. In conclusion, genomic alterations in and/or overexpression of one or more of these proteins are common in both human papillomavirus (HPV)-positive and HPV-negative HNSCC tumors. Therefore, downstream effectors of the PI3K/Akt pathway serve as promising drug targets in the search for novel therapeutic strategies that are able to overcome resistance to anti-EGFR treatment. Co-targeting EGFR and the PI3K/Akt pathway can lead to synergistic drug interactions, possibly restoring sensitivity to EGFR inhibitors and hereby improving clinical efficacy. Better understanding of the predictive value of PI3K/Akt pathway alterations is needed to allow the identification of patient populations that might benefit most from these combination strategies.

A phase I trial of temsirolimus and erlotinib in patients with refractory solid tumors

PURPOSE

Resistance to treatment with inhibitors of mammalian target of rapamycin (mTOR) is partially mediated by activation of epidermal growth factor receptor (EGFR). We conducted a phase I study to determine the recommended phase II dose (RP2D) and dose-limiting toxicities (DLT) of temsirolimus (mTOR inhibitor) combined with erlotinib (EGFR inhibitor) in patients with refractory solid tumors.

METHODS

Standard "3 + 3" design was used for dose escalation. An expansion cohort at RP2D included only patients with squamous histology or mutations relevant to PI3K or EGFR pathway activation. Patients started daily erlotinib 7 days prior to starting temsirolimus on cycle 1. Intravenous temsirolimus was then administered weekly. Starting dose levels were 15 mg for temsirolimus and 100 mg for erlotinib.

RESULTS

Forty-four patients received treatment on this study (28 in dose escalation and 16 in the expansion cohort). The RP2D was temsirolimus 25 mg IV weekly and erlotinib 100 mg orally daily. Two patients experienced DLTs (G3 dehydration and G4 renal failure). The most common drug-related adverse events (all grades) were rash, mucositis/stomatitis, diarrhea, nausea and fatigue. No complete or partial responses were observed. The median duration on this study was 69 days (range 3-770) for escalation and 88 days (range 25-243) for expansion cohorts. Among 11 response-evaluable patients in the expansion cohort, 9 (82%) had stable disease and 2 (18%) had progressive disease.

CONCLUSION

The combination of temsirolimus and erlotinib at the RP2D was well tolerated, and the regimen resulted in prolonged disease stabilization in selected patients (NCT00770263).

Targeting mTOR and Metabolism in Cancer: Lessons and Innovations

Cancer cells support their growth and proliferation by reprogramming their metabolism in order to gain access to nutrients. Despite the heterogeneity in genetic mutations that lead to tumorigenesis, a common alteration in tumors occurs in pathways that upregulate nutrient acquisition. A central signaling pathway that controls metabolic processes is the mTOR pathway. The elucidation of the regulation and functions of mTOR can be traced to the discovery of the natural compound, rapamycin. Studies using rapamycin have unraveled the role of mTOR in the control of cell growth and metabolism. By sensing the intracellular nutrient status, mTOR orchestrates metabolic reprogramming by controlling nutrient uptake and flux through various metabolic pathways. The central role of mTOR in metabolic rewiring makes it a promising target for cancer therapy. Numerous clinical trials are ongoing to evaluate the efficacy of mTOR inhibition for cancer treatment. Rapamycin analogs have been approved to treat specific types of cancer. Since rapamycin does not fully inhibit mTOR activity, new compounds have been engineered to inhibit the catalytic activity of mTOR to more potently block its functions. Despite highly promising pre-clinical studies, early clinical trial results of these second generation mTOR inhibitors revealed increased toxicity and modest antitumor activity. The plasticity of metabolic processes and seemingly enormous capacity of malignant cells to salvage nutrients through various mechanisms make cancer therapy extremely challenging. Therefore, identifying metabolic vulnerabilities in different types of tumors would present opportunities for rational therapeutic strategies. Understanding how the different sources of nutrients are metabolized not just by the growing tumor but also by other cells from the microenvironment, in particular, immune cells, will also facilitate the design of more sophisticated and effective therapeutic regimen. In this review, we discuss the functions of mTOR in cancer metabolism that have been illuminated from pre-clinical studies. We then review key findings from clinical trials that target mTOR and the lessons we have learned from both pre-clinical and clinical studies that could provide insights on innovative therapeutic strategies, including immunotherapy to target mTOR signaling and the metabolic network in cancer.

Phase I study of vinblastine and temsirolimus in pediatric patients with recurrent or refractory solid tumors: Canadian Cancer Trials Group Study IND.218

Combining mammalian target of rapamycin (mTOR) inhibitors and vinca alkaloids has shown therapeutic synergy in xenograft models of pediatric cancers. This phase I study assessed safety and toxicity of temsirolimus in combination with vinblastine in children.

PROCEDURE

Patients ≥ 1 and ≤ 18 years with recurrent/refractory solid or CNS tumors were eligible. Vinblastine (4 mg/m² ) and temsirolimus (15 mg/m² ) were administered i.v. weekly, with planned dose escalation of vinblastine using a rolling six phase I design. Pharmacokinetic and pharmacodynamic data were collected.

RESULTS

Seven patients with median age 12 years (range, 8-18 years) were enrolled; all were evaluable for toxicity and six for response. At dose level 1, four of six patients developed grade 3 mucositis, of which one met duration criteria for dose-limiting toxicity (DLT). Four patients required dose omissions for grade 3 or 4 hematologic toxicity, including one prolonged neutropenia DLT. A subsequent patient was enrolled on dose level -2 (temsirolimus 10 mg/m² , vinblastine 4 mg/m² ) with no protocol-related toxicity > grade 1, except grade 2 neutropenia. Two serious adverse events (SAE) occurred-an allergic reaction to temsirolimus (grade 2) and an intracranial hemorrhage in a CNS tumor patient (grade 3)-unlikely related to study therapy. Soluble VEGFR2 was reduced at cycle 1, day 36 in keeping with inhibition of angiogenesis. Four patients achieved prolonged stable disease for a median of 5.0 months (range, 3.1-8.3 months).

CONCLUSION

The combination of weekly temsirolimus (15 mg/m² ) and vinblastine (4 mg/m² ) exceeds the maximum tolerated dose in children, with frequent oral mucositis and hematologic toxicity.

Functional variant of MTOR rs2536 and survival of Chinese gastric cancer patients

We previously reported that some single nucleotide polymorphisms (SNPs) of candidate genes involved in the MTOR complex1 (MTORC1) were associated with risk of gastric cancer (GCa). In the present study, we further evaluated associations of eight potentially functional SNPs of MTOR, MLST8 and RPTOR with survival of 1002 GCa patients and also investigated molecular mechanisms underlying such associations. Specifically, we found that the MTOR rs2536 C allele at the microRNA binding site was independently associated with a 26% reduction of death risk (HR = 0.74, 95% CI = 0.57-0.96, p = 0.022). The results remained noteworthy with a prior false positive probability of 0.1. Genotype-phenotype correlation analysis in 144 patients' adjacent normal gastric tissue samples revealed that the MTOR expression levels were lower in rs2536 TC/CC carriers than that in wild-type TT carriers (p = 0.043). Dual luciferase assays revealed that the rs2536 C allele had a higher binding affinity to microRNA-150, leading to a decreased transcriptional activity of MTOR, compared to the rs2536 T allele. Further functional analysis revealed that MTOR knockdown by small interference RNA impaired proliferation, migration, and invasion ability in GCa cell lines. In conclusion, The MTOR rs2536 T > C change may be a biomarker for survival of Chinese GCa patients, likely by modulating microRNA-induced gene expression silencing. Additional studies are needed to validate our findings.

Combination of melatonin and rapamycin for head and neck cancer therapy: Suppression of AKT/mTOR pathway activation, and activation of mitophagy and apoptosis via mitochondrial function regulation

Head and neck squamous cell carcinoma (HNSCC) clearly involves activation of the Akt mammalian target of rapamycin (mTOR) signalling pathway. However, the effectiveness of treatment with the mTOR inhibitor rapamycin is often limited by chemoresistance. Melatonin suppresses neoplastic growth via different mechanisms in a variety of tumours. In this study, we aimed to elucidate the effects of melatonin on rapamycin-induced HNSCC cell death and to identify potential cross-talk pathways. We analysed the dose-dependent effects of melatonin in rapamycin-treated HNSCC cell lines (Cal-27 and SCC-9). These cells were treated with 0.1, 0.5 or 1 mmol/L melatonin combined with 20 nM rapamycin. We further examined the potential synergistic effects of melatonin with rapamycin in Cal-27 xenograft mice. Relationships between inhibition of the mTOR pathway, reactive oxygen species (ROS), and apoptosis and mitophagy reportedly increased the cytotoxic effects of rapamycin in HNSCC. Our results demonstrated that combined treatment with rapamycin and melatonin blocked the negative feedback loop from the specific downstream effector of mTOR activation S6K1 to Akt signalling, which decreased cell viability, proliferation and clonogenic capacity. Interestingly, combined treatment with rapamycin and melatonin-induced changes in mitochondrial function, which were associated with increased ROS production, increasing apoptosis and mitophagy. This led to increase cell death and cellular differentiation. Our data further indicated that melatonin administration reduced rapamycin-associated toxicity to healthy cells. Overall, our findings suggested that melatonin could be used as an adjuvant agent with rapamycin, improving effectiveness while minimizing its side effects.

Application of molecular targeted therapies in the treatment of head and neck squamous cell carcinoma

Despite the development of standard therapies, including surgery, radiotherapy and chemotherapy, survival rates for head and neck squamous cell carcinoma (HNSCC) have not changed significantly over the past three decades. Complete recovery is achieved in <50% of patients. The treatment of advanced HNSCC frequently requires multimodality therapy and involves significant toxicity. The promising, novel treatment option for patients with HNSCC is molecular-targeted therapies. The best known targeted therapies include: Epidermal growth factor receptor (EGFR) monoclonal antibodies (cetuximab, panitumumab, zalutumumab and nimotuzumab), EGFR tyrosine kinase inhibitors (gefitinib, erlotinib, lapatinib, afatinib and dacomitinib), vascular endothelial growth factor (VEGF) inhibitor (bevacizumab) or vascular endothelial growth factor receptor (VEGFR) inhibitors (sorafenib, sunitinib and vandetanib) and inhibitors of phosphatidylinositol 3-kinase/serine/threonine-specific protein kinase/mammalian target of rapamycin. There are also various inhibitors of other pathways and targets, which are promising and require evaluation in further studies.