Purpose

Acquired resistance to erlotinib in patients with EGFR-mutant non-small cell lung cancer can result from aberrant activation of alternative receptor tyrosine kinases, such as the HGF-driven c-MET receptor. We sought to determine whether inhibition of AKT signaling could augment erlotinib activity and abrogate HGF-mediated resistance.

Methods

The effects of MK-2206, a selective AKT inhibitor, were evaluated in combination with erlotinib on a large panel of 13 lung cancer cell lines containing different EGFR or KRAS abnormalities. The activity of the combination was assessed using proliferation assays, flow cytometry and immunoblotting. The MEK inhibitor PD0325901 was used to determine the role of the MAP kinase pathway in erlotinib resistance.

Results

The combination of MK-2206 and erlotinib resulted in synergistic growth inhibition independent of EGFR mutation status. In cell lines where HGF blocked the anti-proliferative and cytotoxic effects of erlotinib, MK-2206 could restore cell cycle arrest, but MEK inhibition was required for erlotinib-dependent apoptosis. Both AKT and MEK inhibition contributed to cell death independent of erlotinib in the T790M-containing H1975 and the EGFR-WT cell lines tested.

Conclusions

These findings illustrate the potential advantages and challenges of combined signal transduction inhibition as a generalized strategy to circumvent acquired erlotinib resistance.

Background

Although the epidermal growth factor receptor (EGFR) inhibitor erlotinib is initially effective in non-small-cell lung cancer (NSCLC) patients with tumors harboring activating mutations of EGFR, most subsequently develop acquired resistance. One recognized resistance mechanism occurs through activation of bypass signaling via the hepatocyte growth factor (HGF)-MET pathway. INC-280 is a small molecule kinase inhibitor of MET. We sought to demonstrate the activity of INC-280 on select NSCLC cell lines both as a single agent and in combination with erlotinib using exogenous HGF to simulate MET up-regulation.

Methods

Four NSCLC cell lines (HCC827, PC9, H1666, and H358) were treated with either single-agent INC-280 or in combination with erlotinib with or without HGF. The activity of the drug treatments was measured by cell viability assays. Immunoblotting was used to monitor expression of EGFR/pEGFR, MET/pMET, GAB1/pGAB1, AKT/pAKT, and ERK/pERK as well as markers of apoptosis (PARP and capase-3 cleavage) in H1666, HCC827, and PC9.

Results

As a single agent, INC-280 showed minimal cytotoxicity despite potent inhibition of MET kinase activity at concentrations as low as 10 nM. Addition of HGF prevented erlotinib-induced cell death. The addition of INC280 to HGF-mediated erlotinib-resistant models restored erlotinib sensitivity for all cell lines tested, associated with cleavage of both PARP and caspase-3. In these models, INC-280 treatment was sufficient to restore erlotinib-induced inhibition of MET, GAB1, AKT, and ERK in the presence of HGF.

Conclusion

Although the MET inhibitor INC-280 alone had no discernible effect on cell growth, it was able to restore sensitivity to erlotinib and promote apoptosis in NSCLC models rendered erlotinib resistant by HGF. These data provide a preclinical rationale for an ongoing phase 1 clinical trial of erlotinib plus INC-280 in EGFR-mutated NSCLC.

Despite great progress in understanding lipoprotein physiology, there is still much to be learned about the genetic drivers of lipoprotein abundance, composition, and function. We used ion mobility spectrometry to survey 16 plasma lipoprotein subfractions in 500 Diversity Outbred mice maintained on a Western-style diet. We identified 21 quantitative trait loci (QTL) affecting lipoprotein abundance. To refine the QTL and link them to disease risk in humans, we asked if the human homologs of genes located at each QTL were associated with lipid traits in human genome-wide association studies. Integration of mouse QTL with human genome-wide association studies yielded candidate gene drivers for 18 of the 21 QTL. This approach enabled us to nominate the gene encoding the neutral ceramidase, Asah2, as a novel candidate driver at a QTL on chromosome 19 for large HDL particles (HDL-2b). To experimentally validate Asah2, we surveyed lipoproteins in Asah2-/- mice. Compared to wild-type mice, female Asah2-/- mice showed an increase in several lipoproteins, including HDL. Our results provide insights into the genetic regulation of circulating lipoproteins, as well as mechanisms by which lipoprotein subfractions may affect cardiovascular disease risk in humans.

Glucagon levels increase under homeostatic, fasting conditions, promoting the release of glucose from the liver by accelerating the breakdown of glycogen (also known as glycogenolysis). Glucagon also enhances gluconeogenic flux, including from an increase in the hepatic consumption of amino acids. In type 2 diabetes, dysregulated glucagon signaling contributes to the elevated hepatic glucose output and fasting hyperglycemia that occur in this condition. Yet, the mechanism by which glucagon stimulates gluconeogenesis remains incompletely understood. Contrary to the prevailing belief that glucagon acts primarily on cytoplasmic and nuclear targets, we find glucagon-dependent stimulation of mitochondrial anaplerotic flux from glutamine that increases the contribution of this amino acid to the carbons of glucose generated during gluconeogenesis. This enhanced glucose production is dependent on protein kinase A (PKA) and is associated with glucagon-stimulated calcium release from the endoplasmic reticulum, activation of mitochondrial α-ketoglutarate dehydrogenase, and increased glutaminolysis. Mice with reduced levels of hepatic glutaminase 2 (GLS2), the enzyme that catalyzes the first step in glutamine metabolism, show lower glucagon-stimulated glutamine-to-glucose flux in vivo, and GLS2 knockout results in higher fasting plasma glucagon and glutamine levels with lower fasting blood glucose levels in insulin-resistant conditions. As found in genome-wide association studies (GWAS), human genetic variation in the region of GLS2 is associated with higher fasting plasma glucose; here we show in human cryopreserved primary hepatocytes in vitro that these natural gain-of-function missense mutations in GLS2 result in higher glutaminolysis and glucose production. These data emphasize the importance of gluconeogenesis from glutamine, particularly in pathological states of increased glucagon signaling, while suggesting a possible new therapeutic avenue to treat hyperglycemia.

Purpose

Erlotinib marginally improves survival when administered continuously with gemcitabine to patients with advanced pancreatic cancer; however, preclinical data suggest that there is antagonism between chemotherapy and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors when these are delivered concurrently. We tested a pharmacodynamic separation approach for erlotinib plus gemcitabine and interrogated EGFR signaling intermediates as potential surrogates for the efficacy of this strategy.

Methods

Patients with measurable, previously untreated locally advanced unresectable or metastatic pancreatic cancer were treated with gemcitabine 1000 mg/m(2) as an intravenous infusion over 30-min on days 1, 8, 15 and erlotinib 150 mg/day on days 2-5, 9-12, 16-26 of each 28-day cycle. The primary endpoint was progression-free survival (PFS); secondary endpoints included RECIST objective response rate (ORR) and safety. The study was terminated after thirty patients due to funding considerations.

Results

The median PFS was 2.07 months (95% CI; 1.87-5.50 months) and the ORR was 11%. No unexpected safety signals were seen: the most common grade 3 or higher adverse events were neutropenia (23%), lymphopenia (23%), and fatigue (13%). Patients with mutant plasma Kirsten rat sarcoma virus (KRAS) had significantly lower median PFS (1.8 vs. 4.6 months, p = 0.014) and overall survival (3.0 vs. 10.5 months, p = 0.003) than those without detected plasma KRAS mutations.

Conclusions

Although pharmacodynamically separated erlotinib and gemcitabine were feasible and tolerable in patients with advanced pancreatic cancer, no signal for increased efficacy was seen in this molecularly unselected cohort. Detection of a KRAS mutation in circulating cell-free DNA was a strong predictor of survival.

BACKGROUND: Individuals diagnosed with an obesity-related cancer (ORC survivors) are at an elevated risk of incident diabetes compared with cancer-free individuals, but whether this confers survival disadvantage is unknown. METHODS: We assessed the rate of incident diabetes in ORC survivors and evaluated the association of incident diabetes with all-cause and cancer-specific mortality among females with ORC in the Womens Health Initiative cohort (N = 14,651). Cox proportional hazards regression models stratified by exposure-risk periods (0-1, >1-3, >3-5, >5-7, and >7-10 years) from ORC diagnosis and time-varying exposure (diabetes) analyses were performed. RESULTS: Among the ORC survivors, a total of 1.3% developed diabetes within ≤1 year of follow-up and 2.5%, 2.3%, 2.3%, and 3.6% at 1-3, 3-5, 5-7, and 7-10 years of follow-up, respectively, after an ORC diagnosis. The median survival for those diagnosed with diabetes within 1-year of cancer diagnosis and those with no diabetes diagnosis in that time frame was 8.8 [95% confidence interval (CI), 7.0-14.5) years and 16.6 (95% CI, 16.1-17.0) years, respectively. New-onset compared with no diabetes as a time-varying exposure was associated with higher risk of all-cause (HR, 1.27; 95% CI, 1.16-1.40) and cancer-specific (HR, 1.17; 95% CI, 0.99-1.38) mortality. When stratified by exposure-risk periods, incident diabetes in ≤1 year of follow-up was associated with higher all-cause (HR, 1.76; 95% CI, 1.40-2.20) and cancer-specific (HR0-1, 1.82; 95% CI, 1.28-2.57) mortality, compared with no diabetes diagnosis. CONCLUSIONS: Incident diabetes was associated with worse cancer-specific and all-cause survival, particularly in the year after cancer diagnosis. IMPACT: These findings draw attention to the importance of diabetes prevention efforts among cancer survivors to improve survival outcomes.

Type 2 diabetes mellitus (T2DM) is a common complication of obesity. Here, we have shown that activation of the IgG receptor FcγRIIB in endothelium by hyposialylated IgG plays an important role in obesity-induced insulin resistance. Despite becoming obese on a high-fat diet (HFD), mice lacking FcγRIIB globally or selectively in endothelium were protected from insulin resistance as a result of the preservation of insulin delivery to skeletal muscle and resulting maintenance of muscle glucose disposal. IgG transfer in IgG-deficient mice implicated IgG as the pathogenetic ligand for endothelial FcγRIIB in obesity-induced insulin resistance. Moreover, IgG transferred from patients with T2DM but not from metabolically healthy subjects caused insulin resistance in IgG-deficient mice via FcγRIIB, indicating that similar processes may be operative in T2DM in humans. Mechanistically, the activation of FcγRIIB by IgG from obese mice impaired endothelial cell insulin transcytosis in culture and in vivo. These effects were attributed to hyposialylation of the Fc glycan, and IgG from T2DM patients was also hyposialylated. In HFD-fed mice, supplementation with the sialic acid precursor N-acetyl-D-mannosamine restored IgG sialylation and preserved insulin sensitivity without affecting weight gain. Thus, IgG sialylation and endothelial FcγRIIB may represent promising therapeutic targets to sever the link between obesity and T2DM.

The biophysical environment of membrane phospholipids affects structure, function, and stability of membrane-bound proteins.^1,2 Obesity can disrupt membrane lipids, and in particular, alter the activity of sarco/endoplasmic reticulum (ER/SR) Ca²⁺-ATPase (SERCA) to affect cellular metabolism.^3-5 Recent evidence suggests that transport efficiency (Ca²⁺ uptake / ATP hydrolysis) of skeletal muscle SERCA can be uncoupled to increase energy expenditure and protect mice from diet-induced obesity.^6,7 In isolated SR vesicles, membrane phospholipid composition is known to modulate SERCA efficiency.^8-11 Here we show that skeletal muscle SR phospholipids can be altered to decrease SERCA efficiency and increase whole-body metabolic rate. The absence of skeletal muscle phosphatidylethanolamine (PE) methyltransferase (PEMT) promotes an increase in skeletal muscle and whole-body metabolic rate to protect mice from diet-induced obesity. The elevation in metabolic rate is caused by a decrease in SERCA Ca²⁺-transport efficiency, whereas mitochondrial uncoupling is unaffected. Our findings support the hypothesis that skeletal muscle energy efficiency can be reduced to promote protection from obesity.

Aberrant lipid metabolism promotes the development of skeletal muscle insulin resistance, but the exact identity of lipid-mediated mechanisms relevant to human obesity remains unclear. A comprehensive lipidomic analysis of primary myocytes from individuals who were insulin-sensitive and lean (LN) or insulin-resistant with obesity (OB) revealed several species of lysophospholipids (lyso-PLs) that were differentially abundant. These changes coincided with greater expression of lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme involved in phospholipid transacylation (Lands cycle). Strikingly, mice with skeletal muscle-specific knockout of LPCAT3 (LPCAT3-MKO) exhibited greater muscle lysophosphatidylcholine/phosphatidylcholine, concomitant with improved skeletal muscle insulin sensitivity. Conversely, skeletal muscle-specific overexpression of LPCAT3 (LPCAT3-MKI) promoted glucose intolerance. The absence of LPCAT3 reduced phospholipid packing of cellular membranes and increased plasma membrane lipid clustering, suggesting that LPCAT3 affects insulin receptor phosphorylation by modulating plasma membrane lipid organization. In conclusion, obesity accelerates the skeletal muscle Lands cycle, whose consequence might induce the disruption of plasma membrane organization that suppresses muscle insulin action.