William S. Holland

EGFR Mutations Detected in Plasma Are Associated with Patient Outcomes in Erlotinib Plus Docetaxel-Treated Non-small Cell Lung Cancer

Purpose: Activating mutations in the epidermal growth factor receptor (EGFR) are associated with enhanced response to EGFR tyrosine kinase inhibitors in non-small cell lung cancer (NSCLC), whereas KRAS mutations translate into poor patient outcomes. We hypothesized that analysis of plasma for EGFR and KRAS mutations from shed tumor DNA would have clinical utility. Methods: An allele-specific polymerase chain reaction assay using Scorpion-amplification refractory mutation system (DxS, Ltd) was used to detect mutations in plasma DNA from patients with advanced stage NSCLC treated as second- or third-line therapy on a phase I/II trial of docetaxel plus intercalated erlotinib. Results: EGFR mutations were detected in 10 of 49 patients (20%). Six (12%) had single activating mutations in EGFR, associated with improved progression-free survival (median, 18.3 months), compared with all other patients (median, 3.9 months; p = 0.008), or those with wild-type EGFR (median, 4.0 months; p = 0.012). Four of 49 patients harbored a de novo T790M resistance mutation (median progression-free survival, 3.9 months). EGFR mutational status was associated with clinical response (45 assessable, p = 0.0001); in the six patients with activating mutations, all achieved complete (33%) or partial (67%) response. All CR patients had E19del detectable in both tumor and plasma. KRAS mutations were detected in two of 49 (4%) patients, both of whom had rapid progressive disease. Conclusions: Activating EGFR mutations detected in shed DNA in plasma are significantly associated with favorable outcomes in patients with advanced NSCLC receiving docetaxel plus intercalated erlotinib. The addition of docetaxel in this schedule did not diminish the efficacy of erlotinib against patients with EGFR activating mutations.

Multidrug-resistant protein-3 gene regulation by the transcription factor Nrf2 in human bronchial epithelial and non-small-cell lung carcinoma

Multidrug-resistant proteins (MRPs) are members of the ATP-binding cassette superfamily that facilitate detoxification by transporting toxic compounds, including chemotherapeutic drugs, out of cells. Chemotherapy, radiation, and other xenobiotic stresses have been shown to increase levels of select MRPs, although the underlying mechanism remains largely unknown. Additionally, MRP3 is suspected of playing a role in the drug resistance of non-small-cell lung carcinoma (NSCLC). Analysis of the MRP3 promoter revealed the presence of multiple putative electrophile-responsive elements (EpREs), sequences that suggest possible regulation of this gene by Nrf2, the key transcription factor that binds to EpRE. The goal of this investigation was to determine whether MRP3 induction was dependent upon the transcription factor Nrf2. Keap1, a key regulator of Nrf2, sequesters Nrf2 in the cytoplasm, preventing entry into the nucleus. The electrophilic lipid peroxidation product 4-hydroxy-2-nonenal (HNE) has been shown to modify Keap1, allowing Nrf2 to enter the nucleus. We found that HNE up-regulated MRP3 mRNA and protein levels in cell lines with wild-type Keap1 (the human bronchial epithelial cell line HBE1 and the NSCLC cell line H358), but not in the Keap1-mutant NSCLC cell lines (A549 and H460). Cell lines with mutant Keap1 had constitutively higher MRP3 that was not increased by HNE treatment. In HBE1 cells, silencing of Nrf2 with siRNA inhibited induction of MRP3 by HNE. Finally, we found that silencing Nrf2 also increased the toxicity of cisplatin in H358 cells. The combined results therefore support the hypothesis that MRP3 induction by HNE involves Nrf2 activation.

Genistein combined polysaccharide enhances activity of docetaxel, bicalutamide and Src kinase inhibition in androgen-dependent and independent prostate cancer cell lines.

To determine the benefit of genistein combined polysaccharide (GCP) in combination with the androgen receptor antagonist bicalutamide, the antimicrotubule taxane docetaxel, and the Src kinase inhibitor pp2 as part of a treatment regimen for advanced prostate cancer (CaP).

Anti‐tumor activity of the HSP90 inhibitor SNX‐2112 in pediatric cancer cell lines

HSP90 plays a central role in stabilizing client proteins involved in malignant processes. SNX‐2112 is an orally administered potent HSP90 inhibitor that has demonstrated pre‐clinical anti‐tumor activity in adult malignancies. As many childhood tumors depend upon HSP90 client proteins, we sought to test the pre‐clinical efficacy of SNX‐2112 in a panel of pediatric cancer cell lines both as a single‐agent and in combination with cisplatin (CP).

Aberrant Regulation of the MRP3 Gene in Non-small Cell Lung Carcinoma

Introduction: Multidrug-resistant protein-3 (MRP3), a membrane-bound transporter, facilitates efflux of toxic compounds, including certain chemotherapies, out of cells. Aberrant MRP3 expression has been linked to drug resistance in non-small cell lung carcinoma (NSCLC). We sought to determine if tumor MRP3 expression patterns correlate with the mutational status of upstream regulators, including nuclear factor erythroid-2-related factor 2 (Nrf2) and its functional repressor Keap1 in NSCLC cell lines and patient samples. Methods: To identify putative Nrf2-binding sites in the MRP3 promoter and to evaluate Keap1, Nrf2, and p53 mutation status in four cell lines and 33 NSCLC surgically resected tumor specimens with regard to their impact on MRP3 levels. Results: Chromatin immunoprecipitation analysis of the MRP3 promoter revealed an almost threefold increase in Nrf2 binding to the third putative Nrf2-binding sequence distal to the start site, demonstrating direct regulation of MRP3 by Nrf2. In NSCLC cell lines, elevated Nrf2 protein was observed in cell lines with increased MRP3 RNA expression. In patient tumor specimens, the presence of mutations in Keap1/Nrf2 correlated with MRP3 RNA levels (p < 0.05). p53 mutations were observed in 33% of cases, and all Keap1 mutant-positive tumors possessed a p53 mutation (n = 5; p = 0.0019). Conclusions: We demonstrate direct involvement between the transcription factor Nrf2 and the MRP3 promoter, which leads to the up-regulation of the MRP3 gene. In addition, we found a statistically significant correlation between the presence of Keap1/Nrf2 mutations and increased MRP3 messenger RNA levels in our NSCLC patient samples.

Anticancer activity of the Aurora A kinase inhibitor MK-5108 in non-small-cell lung cancer (NSCLC) in vitro as monotherapy and in combination with chemotherapies

AbstractPurpose Aurora kinases are key regulators of mitotic events. Dysfunction of these kinases can cause polyploidy and chromosomal instability, a contributor to tumorigenesis. MK-5108 is a potent inhibitor of Aurora A kinase that has shown preclinical potent activity in malignancies of breast, cervical, colon, ovarian, and pancreatic origin. We sought to assess the preclinical efficacy of MK-5108 in a panel of non-small-cell lung cancer cell lines as a single agent and in combination with cisplatin and docetaxel.MethodsEleven lung cancer cell lines were studied. Growth inhibition by MK-5108 was assessed with short- and long-term MTT assays. Cell cycling was measured by flow cytometry. Immunoblotting was used to determine targeted activity of MK-5108 on Aurora A and downstream effects (TACC3 and Plk1). Efficacy of combination studies performed with cisplatin and docetaxel was evaluated by median effect analysis.ResultsAll cell lines demonstrated sustained growth inhibition following MK-5108 at varying nanomolar concentrations. MK-5108 induced G2/M accumulation, polyploidy, and apoptosis (increased sub-G1/PARP cleavage). Levels of Aurora A, TACC3, and Plk1 diminished. Concurrent treatment of MK-5108 with cisplatin or docetaxel synergistically inhibited cell growth with the docetaxel combination performing better. When administered sequentially, treatment with docetaxel first followed by MK-5108 exhibited greater growth inhibition than the inverse; yet concurrent treatment remained superior.ConclusionsMK-5108 has potent anti-proliferative activity in lung cancer cell lines alone and in combination with chemotherapies. Determining how best to integrate Aurora inhibitors into current lung cancer treatment regimens would be beneficial.

Effects of AKT inhibition on HGF-mediated erlotinib resistance in non-small cell lung cancer cell lines

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

Preclinical Evaluation of MET Inhibitor INC-280 With or Without the Epidermal Growth Factor Receptor Inhibitor Erlotinib in Non-Small-Cell Lung Cancer.

Micro‐Abstract The MET inhibitor INC‐280 restored sensitivity to erlotinib and promoted apoptosis in non–small‐cell lung cancer models rendered resistant to erlotinib by hepatocyte growth factor. 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.