Drugging the bad "AKT-TOR" to overcome TKI-resistant lung cancer

Epidermal Growth Factor Receptor Expression and Resistance Patterns to Targeted Therapy in Non-Small Cell Lung Cancer: A Review

Globally, lung cancer is the leading cause of cancer-related death. The majority of non-small cell lung cancer (NSCLC) tumours express epidermal growth factor receptor (EGFR), which allows for precise and targeted therapy in these patients. The dysregulation of EGFR in solid epithelial cancers has two distinct mechanisms: either a kinase-activating mutation in EGFR (EGFR-mutant) and/or an overexpression of wild-type EGFR (wt-EGFR). The underlying mechanism of EGFR dysregulation influences the efficacy of anti-EGFR therapy as well as the nature of resistance patterns and secondary mutations. This review will critically analyse the mechanisms of EGFR expression in NSCLC, its relevance to currently approved targeted treatment options, and the complex nature of secondary mutations and intrinsic and acquired resistance patterns in NSCLC.

Gamma-synuclein binds to AKT and promotes cancer cell survival and proliferation

Hyperactivation of AKT plays a critical role in the survival and proliferation of cancer cells. However, the molecular mechanisms underlying AKT activation remain elusive. Here, we tested the effect of γ-synuclein, a member of the synuclein family of proteins, on the activation of AKT. We show that the expression level of γ-synuclein is increased in non-small cell lung cancer (NSCLC) tissues. γ-Synuclein binds to the protein kinase domain of AKT and promotes its phosphorylation. Overexpression of γ-synuclein in H157 cells enhances cell proliferation and protects the cells from staurosporine-induced cytotoxicity. Knockdown of γ-synuclein attenuates AKT activation and cell proliferation induced by epidermal growth factor. The effect of γ-synuclein is abolished when AKT is depleted. Thus, γ-synuclein promotes cell survival and proliferation via activating AKT and may play a causal role in the pathogenesis of NSCLC.

Antiproliferative effect of a novel mTOR inhibitor temsirolimus contributes to the prolonged survival of orthotopic esophageal cancer-bearing mice

Esophageal squamous cell carcinoma (ESCC) remains one of the most aggressive cancers with poor prognosis regardless of a several reports that indicate a better therapeutic efficacy using some new chemotherapeutic agents. Recent drug development has contributed to an improved specificity to suppress mTOR activity by which many types of malignancies can be explosively progressed. Temsirolimus (CCI-779, TricelTM) is one of recently synthesized analogs of rapamycin and has provided better outcomes for patients with renal cell carcinoma. In this study, we experimentally evaluated an efficacy of targeting mTOR by temsirolimus for ESCC treatment, with an assessment of its survival advantage using an advanced ESCC animal model. First, we confirmed that the expression of phosphorylated mTOR was increased in 46 of 58 clinical ESCC tumor tissues (79.3%) and appeared to get strengthened with tumor progression. All of ESCC cell lines used in this study revealed an increase of mTOR phosphorylation, accompanied with the upregulation of hypoxia inducible factor-I α (HIF-1α), one of the critical effectors regulated by mTOR. Temsirolimus treatment apparently suppressed the activation of mTOR and its downstream effectors, resulting in the reduced ability of ESCC cell proliferation. Finally, the weekly administration of temsirolimus significantly diminished the size of subcutaneous tumors (vehicle, 3261.6 ± 722.0; temsirolimus, 599.2 ± 122.9; p = 0.007) in nude mice and effectively prolonged orthotopic esophageal cancer-bearing mice (median survival periods: control, 31 d; temsirolimus, 43 d; p = 0.0024). These data suggests that targeting mTOR by temsirolimus may become a therapeutic alternative for esophageal cancer, with a contribution to a better outcome.

Efficient blockade of Akt signaling is a determinant factor to overcome resistance to matuzumab

BACKGROUND

Clinical studies have shown antineoplastic effectiveness of monoclonal antibodies (MAbs) against EGFR for different indications. Several MAbs directed to EGFR were developed recently, such as matuzumab, but there is still lack of information on preclinical data on its combination with chemo-radiation. Thus, the present study intended to examine the molecular pathways triggered by matuzumab alone or associated to chemo-radiotherapy in gynecological cell lines and its impact on cell growth and signaling.

RESULTS

Combination of matuzumab with radiation and cisplatin did not enhance its cytostatic effects on A431, Caski and C33A cells (high, intermediate and low EGFR expression, respectively) in clonogenic assays, when compared to controls. The lack of effect was mediated by persistent signaling through EGFR due to its impaired degradation. In spite of the fact that matuzumab inhibited phosphorylation of EGFR, it had no effect upon cell viability. To analyze which downstream molecules would be involved in the EGFR signaling in the presence of matuzumab, we have tested it in combination with either PD98059 (MAPK inhibitor), or LY294002 (PI3K inhibitor). Matuzumab exhibited a synergic effect with LY294002, leading to a reduction of Akt phosphorylation that was followed by a decrease in A431 and Caski cells survival. The combination of PD98059 and matuzumab did not show the same effect suggesting that PI3K is an important effector of EGFR signaling in matuzumab-treated cells. Nonetheless, matuzumab induced ADCC in Caski cells, but not in the C33A cell line, suggesting that its potential therapeutic effects in vitro are indeed dependent on EGFR expression.

CONCLUSIONS

Matuzumab combined with chemoradiation did not induce cytotoxic effects on gynecological cancer cell lines in vitro, most likely due to impaired EGFR degradation. However, a combination of matuzumab and PI3K inhibitor synergistically inhibited pAkt and cell survival, suggesting that the use of PI3K/Akt inhibitors could overcome intrinsic resistance to matuzumab in vitro. Altogether, data presented here can pave the way to a rational design of clinical strategies in patients with resistant profile to anti-EGFR inhibitors based on combination therapy.

In vivo characterization of a polymeric nanoparticle platform with potential oral drug delivery capabilities

Nanotechnology has enabled significant advances in the areas of cancer diagnosis and therapy. The field of drug delivery is a sterling example, with nanoparticles being increasingly used for generating therapeutic formulations of poorly water-soluble, yet potent anticancer drugs. Whereas a number of nanoparticle-drug combinations are at various stages of preclinical or clinical assessment, the overwhelming majorities of such systems are injectable formulations and are incapable of being partaken orally. The development of an oral nano-delivery system would have distinct advantages for cancer chemotherapy. We report the synthesis and physicochemical characterization of orally bioavailable polymeric nanoparticles composed of N-isopropylacrylamide, methylmethacrylate, and acrylic acid in the molar ratios of 60:20:20 (designated NMA622). Amphiphilic NMA622 nanoparticles show a size distribution of <100 nm (mean diameter of 80 +/- 34 nm) with low polydispersity and can readily encapsulate a number of poorly water-soluble drugs such as rapamycin within the hydrophobic core. No apparent systemic toxicities are observed in mice receiving as much as 500 mg/kg of the orally administered void NMA622 for 4 weeks. Using NMA622-encapsulated rapamycin ("nanorapamycin") as a prototype for oral nano-drug delivery, we show favorable in vivo pharmacokinetics and therapeutic efficacy in a xenograft model of human pancreatic cancer. Oral nanorapamycin leads to robust inhibition of the mammalian target of rapamycin pathway in pancreatic cancer xenografts, which is accompanied by significant growth inhibition (P < 0.01) compared with control tumors. These data indicate that NMA622 nanoparticles provide a suitable platform for oral delivery of water-insoluble drugs like rapamycin for cancer therapy.

Anticancer therapeutics: A surge of new developments increasingly target tumor and stroma

The Annual Meeting of the American Association for Cancer Research (AACR) brings together research in fundamental biology, translational science, drug development and clinical testing of emerging anticancer therapies. Among the highlights of the 2007 Annual Meeting were major research themes on drug action, drug resistance and new drug development. Instead of striving for a comprehensive overview, we showcase several trends, concepts and research areas that exemplify the complexity of drug resistance and its reversal as we currently understand it. Many of the studies discussed here deal with the interaction of tumor cells with their stromal microenvironment; structural proteins as well as cellular components, fibroblasts as well as inflammatory cells. Target identification, target validation and dealing with the challenge of resistance are recurring themes. Specific classes of molecules discussed are the taxanes, tyrosine kinase inhibitors, anti-angiogenic, anti-stromal and anti-metastatic agents. In the latter three categories, targets reviewed are delta-like ligand 4 (DLL4), integrins, nodal, galectins, lysyl oxidases and thrombospondins, several of which belong to the p53-tumor suppressor repertoire of secreted proteins. Finally, developments in other inhibitor classes such as PI3K/Akt and Rho GTPase inhibitors and thoughts on possible novel combination therapies are briefly summarized. The report also includes relevant publications to July 2007.