Lung cancer management: monitoring and treating resistance development in third-generation EGFR TKIs

INTRODUCTION

Patients treated with third-generation EGFR TKIs will develop resistance to treatment at a certain point. Early detection of resistance occurrence could allow more options for treatment.

AREAS COVERED

We discuss the development of third-generation EGFR TKIs, focusing on osimertinib and discuss the most common resistance mechanisms under evaluation. We also debate how this resistance can be detected; particularly we review the possible application of liquid biopsy in this scenario. Lastly we discuss available treatment options when resistance occurs, with an eye on ongoing trials and possible future developments.

EXPERT OPINION

As resistance will ultimately develop, a strict instrumental follow-up as per international guidelines is required with the aim of detecting this resistance in an early phase. Detecting an oligoprogression could allow the integration of local ablative therapies while further delaying the need for a systemic therapy change. By exploiting the increasing potentiality of liquid biopsy, in the near future, physicians could be able to understand why a patient develops resistance and therefore can choose the best possible individualized treatment option.

The use of radiation therapy for oligoprogressive/oligopersistent oncogene-driven non small cell lung cancer: State of the art

Oncogene-driven non small cell lung cancer (NSCLC) is a distinct entity in thoracic oncology. The availability of effective target therapies, like EGFR inhibitors or ALK inhibitors, have revolutionized the prognosis of these patients. However, despite an initial response in the majority of patients, drug resistance ultimately occurs. In some cases, this resistance develops in few clonal cells (oligoprogression), so that a local ablation of these resistant deposits could allow to maintain the same systemic therapy and possibly to prolong patients' survival. For these purposes, stereotactic body radiation therapy (SBRT) is an ideal local ablative treatment, because it is effective, non invasive and with limited side effects. In this review, we aim to analyze available clinical data to verify whether SBRT can allow these patients to continue with existing target therapy longer, delay the switch to other systemic therapies and improve their outcome modifying the natural history of the disease.

Preclinical Efficacy of the Novel Monocarboxylate Transporter 1 Inhibitor BAY-8002 and Associated Markers of Resistance

The lactate transporter SLC16A1/monocarboxylate transporter 1 (MCT1) plays a central role in tumor cell energy homeostasis. In a cell-based screen, we identified a novel class of MCT1 inhibitors, including BAY-8002, which potently suppress bidirectional lactate transport. We investigated the antiproliferative activity of BAY-8002 in a panel of 246 cancer cell lines and show that hematopoietic tumor cells, in particular diffuse large B-cell lymphoma cell lines, and subsets of solid tumor models are particularly sensitive to MCT1 inhibition. Associated markers of sensitivity were, among others, lack of MCT4 expression, low pleckstrin homology like domain family A member 2, and high pellino E3 ubiquitin protein ligase 1 expression. The antitumor effect of MCT1 inhibition was less pronounced on tumor xenografts, with tumor stasis being the maximal response. BAY-8002 significantly increased intratumor lactate levels and transiently modulated pyruvate levels. In order to address potential acquired resistance mechanisms to MCT1 inhibition, we generated MCT1 inhibitor-resistant cell lines and show that resistance can occur by upregulation of MCT4 even in the presence of sufficient oxygen, as well as by shifting energy generation toward oxidative phosphorylation. These findings provide insight into novel aspects of tumor response to MCT1 modulation and offer further rationale for patient selection in the clinical development of MCT1 inhibitors. Mol Cancer Ther; 17(11); 2285-96. ©2018 AACR.

Surrogate Predictive Biomarkers for Response to Anti-EGFR Agents: State of the Art and Challenges

The epidermal growth factor receptor (EGFR) plays a key role in cancer development and progression in several human malignancies including non-small cell lung cancer (NSCLC). Several strategies aimed at inhibiting the EGFR have been investigated in the last years, including the use of small tyrosine kinase inhibitors (TKIs) directed against the intracellular domain of the receptor and monoclonal antibodies targeting its extracellular portion. Subgroups of patients who are more likely to respond to TKIs have been identified based on both clincal and biological features. Never-smoking history has emerged as the most relevant clinical characteristic predictive of response to TKIs in NSCLC, while presence of drug-sensitive EGFR mutations and EGFR gene gain represent critical biological variables associated with an improved outcome for patients exposed to these agents. Recent studies have highlighted the existence of biological factors involved in intrinsic and acquired resistance to TKIs, including k-ras, HER-2 and EGFR exon 20 mutations. Increasing knowledge of EGFR biology and drug-receptor interactions will allow to identify individuals who are likely to derive a clinical benefit from the proposed targeted therapy, sparing refractory patients expensive and potentially toxic treatment.

Pan-mutant IDH1 inhibitor BAY 1436032 for effective treatment of IDH1 mutant astrocytoma in vivo

Mutations in codon 132 of isocitrate dehydrogenase (IDH) 1 are frequent in diffuse glioma, acute myeloid leukemia, chondrosarcoma and intrahepatic cholangiocarcinoma. These mutations result in a neomorphic enzyme specificity which leads to a dramatic increase of intracellular D-2-hydroxyglutarate (2-HG) in tumor cells. Therefore, mutant IDH1 protein is a highly attractive target for inhibitory drugs. Here, we describe the development and properties of BAY 1436032, a pan-inhibitor of IDH1 protein with different codon 132 mutations. BAY 1436032 strongly reduces 2-HG levels in cells carrying IDH1-R132H, -R132C, -R132G, -R132S and -R132L mutations. Cells not carrying IDH mutations were unaffected. BAY 1436032 did not exhibit toxicity in vitro or in vivo. The pharmacokinetic properties of BAY 1436032 allow for oral administration. In two independent experiments, BAY 1436032 has been shown to significantly prolong survival of mice intracerebrally transplanted with human astrocytoma carrying the IDH1R132H mutation. In conclusion, we developed a pan-inhibitor targeting tumors with different IDH1R132 mutations.

Effect of oncogene activating mutations and kinase inhibitors on amino acid metabolism of human isogenic breast cancer cells

We investigated the changes in amino acid (AA) metabolism induced in MCF10A, a human mammary epithelial cell line, by the sequential knock-in of K-Ras and PI3K mutant oncogenes. Differentially regulated genes associated to AA pathways were identified on comparing gene expression patterns in the isogenic cell lines. Additionally, we monitored the changes in the levels of AAs and transcripts in the cell lines treated with kinase inhibitors (REGO: a multi-kinase inhibitor, PI3K-i: a PI3K inhibitor, and MEK-i: a MEK inhibitor). In total, 19 AAs and 58 AA-associated transcripts were found to be differentially regulated by oncogene knock-in and by drug treatment. In particular, the multi-kinase and MEK inhibitor affected pathways in K-Ras mutant cells, whereas the PI3K inhibitor showed a major impact in the K-Ras/PI3K double mutant cells. These findings may indicate the dependency of AA metabolism on the oncogene mutation pattern in human cancer. Thus, future therapy might include combinations of kinase inhibitors and drug targeting enzymes of AA pathways.

Abstract 3790: Targeting the one-carbon metabolism protein MTHFD2 for cancer therapy: Exploiting the unique redox status of cancer cells

Two well-established hallmarks of cancer are the need for nucleotides to support continuous cell proliferation and the requirement for cancer cell redox balance. In that respect cancer cells are characterized by an increased rate of reactive oxygen species (ROS) production which can be toxic to cancer cells. In this sense, cancer cells often display an increased ROS scavenging capacity, through antioxidants and NADPH that prevents ROS levels from reaching cytotoxic levels. Mitochondrial methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is a critical component of one-carbon metabolism and promotes the reaction of 5, 10-methylene tetrahydrofolate to 10-formyl tetrahydrofolate which is coupled to purine synthesis and the production of NAD(P)H. In its role, MTHFD2 is required for maintaining nucleotide biosynthesis and cancer cell redox balance. Recent studies have shown that MTHFD2 expression is elevated in many cancers compared to normal tissue and expression is correlated with poor survival in breast cancer. In order to validate MTHFD2 as a potential cancer target we show that genetic knockdown of MTHFD2 led to impaired cancer cell survival and proliferation. In breast cancer cells MTHFD2 inhibition caused a decrease in NADPH, an increase in the levels of oxidized glutathione and also promoted the expression of DNA damage and death markers specifically in cancer cells with high MTHFD2 protein expression. Interestingly, ROS-scavenging antioxidants reversed these phenotypes in the presence of MTHFD2 knockdown. Normal cells and low MTHFD2 expressing breast cancer cells had a higher tolerance for the inhibition of the protein. Based on our data, MTHFD2 inhibition leads to the impairment of cancer cells’ antioxidant capacity and ROS-mediated cell death. Therefore, MTHFD2 inhibition may have clinical potential for the treatment of patients with breast cancer, and potentially various other cancers.

Citation Format: Andrea Glasauer, Michael Steckel, Andrea Haegebarth, Marcus Bauser, Luisella Toschi. Targeting the one-carbon metabolism protein MTHFD2 for cancer therapy: Exploiting the unique redox status of cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3790.

Abstract 4746: Pharmacological characterization of BAY-876, a novel highly selective inhibitor of glucose transporter (GLUT)-1 in vitro and in vivo

One hallmark of cancer is the accelerated metabolism, high energy requirements, and increased glucose uptake by the tumor cells, the latter being the first and rate-limiting step for glucose metabolism. Glucose transport into the tumor cell is mediated by facilitative high-affinity glucose transporter (GLUT) proteins. Among the 14 GLUT proteins, expression of GLUT1 in normal organs is nearly exclusively restricted to the blood brain barrier, while other GLUTs are also expressed in a wide variety of vital organs such as liver and heart. Interestingly, GLUT1 expression is highly regulated by hypoxia-inducible factor (HIF)-1α, a key driver of tumor progression. In line with this finding, GLUT1 over-expression was found to be associated with tumor progression and poor overall survival in various tumor indications. Consequently, GLUT1 represents a potential target for cancer treatment. Therefore, we have developed a highly-selective GLUT1 inhibitor, namely BAY-876, with selectivity over GLUT2, 3, and 4 of 4700-, 800-, and 135-fold, respectively. We here show for the first time the pharmacological characterization of BAY-876, comprising inhibition of glucose-uptake, anti-proliferative activity in vitro, and anti-tumor efficacy in vivo in models of different tumor indications in monotherapy as well as first results on the combinability of BAY-876. Furthermore, at the therapeutic dose, BAY-876 treatment did not show any relevant finding on the behavior of treated mice in the Irwin test, assuming no or only minor effects on brain function. In conclusion, BAY-876 is the first GLUT1-selective inhibitor which reduces glucose uptake and growth of tumor cells with sufficient tolerability at the efficacious dose in preclinical models.

Citation Format: Charlotte Kopitz, Luisella Toschi, Carolyn Algire, Mélanie Héroult, Anna-Lena Frisk, Kirstin Meyer, Arndt Schmitz, Eleni Lagkadinou, Heike Petrul, Iring Heisler, Roland Neuhaus, Bernd Buchmann, Herbert Himmel, Marcus Bauser, Andrea Haegebarth, Karl Ziegelbauer. Pharmacological characterization of BAY-876, a novel highly selective inhibitor of glucose transporter (GLUT)-1 in vitro and in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4746.

Predictive biomarker discovery through the parallel integration of clinical trial and functional genomics datasets

The European Union multi-disciplinary Personalised RNA interference to Enhance the Delivery of Individualised Cytotoxic and Targeted therapeutics (PREDICT) consortium has recently initiated a framework to accelerate the development of predictive biomarkers of individual patient response to anti-cancer agents. The consortium focuses on the identification of reliable predictive biomarkers to approved agents with anti-angiogenic activity for which no reliable predictive biomarkers exist: sunitinib, a multi-targeted tyrosine kinase inhibitor and everolimus, a mammalian target of rapamycin (mTOR) pathway inhibitor. Through the analysis of tumor tissue derived from pre-operative renal cell carcinoma (RCC) clinical trials, the PREDICT consortium will use established and novel methods to integrate comprehensive tumor-derived genomic data with personalized tumor-derived small hairpin RNA and high-throughput small interfering RNA screens to identify and validate functionally important genomic or transcriptomic predictive biomarkers of individual drug response in patients. PREDICT's approach to predictive biomarker discovery differs from conventional associative learning approaches, which can be susceptible to the detection of chance associations that lead to overestimation of true clinical accuracy. These methods will identify molecular pathways important for survival and growth of RCC cells and particular targets suitable for therapeutic development. Importantly, our results may enable individualized treatment of RCC, reducing ineffective therapy in drug-resistant disease, leading to improved quality of life and higher cost efficiency, which in turn should broaden patient access to beneficial therapeutics, thereby enhancing clinical outcome and cancer survival. The consortium will also establish and consolidate a European network providing the technological and clinical platform for large-scale functional genomic biomarker discovery. Here we review our current understanding of molecular mechanisms driving resistance to anti-angiogenesis agents, the current limitations of laboratory and clinical trial strategies and how the PREDICT consortium will endeavor to identify a new generation of predictive biomarkers.

Insulin-like growth factor receptor 1 (IGF1R) expression and survival in surgically resected non-small-cell lung cancer (NSCLC) patients

BACKGROUND

The purpose of this study is to investigate the prognostic role of insulin-like growth factor receptor 1 (IGF1R) expression in surgically resected non-small-cell lung cancer (NSCLC). Patient characteristics and methods: This retrospective study was conducted in 369 stage I-II-IIIA, surgically resected, NSCLC patients. Patients exposed to anti-epidermal growth factor receptor (EGFR) agents were excluded. IGF1R expression was evaluated by immunohistochemistry in tissue microarray sections.

RESULTS

A positive IGF1R expression (score > or = 100) was observed in 282 cases (76.4%) and was significantly associated with squamous cell histology (P = 0.04) and with grade III differentiation (P = 0.02). No difference in survival was observed between the positive and negative group when score 100 was used as cut-off for discriminating a positive versus a negative IGF1R result (52 versus 48 months, P = 0.99) or when median value of IGF1R expression was used (45 versus 55 months, P = 0.36). No difference in survival was observed between IGF1R-positive and -negative patients in a subgroup of stage I-II adenocarcinoma (n = 137) with known EGFR mutation and copy number status.

CONCLUSIONS

IGF1R expression does not represent a prognostic factor in resected NSCLC patients. Patients with squamous cell carcinoma overexpress IGF1R more frequently than patients with nonsquamous histology, justifying the different sensitivity to anti-IGF1R agents observed in clinical trials.

MET increased gene copy number and primary resistance to gefitinib therapy in non-small-cell lung cancer patients

BACKGROUND

MET amplification has been detected in approximately 20% of non-small-cell lung cancer patients (NSCLC) with epidermal growth factor receptor (EGFR) mutations progressing after an initial response to tyrosine kinase inhibitor (TKI) therapy.

PATIENTS AND METHODS

We analyzed MET gene copy number using FISH in two related NSCLC cell lines, one sensitive (HCC827) and one resistant (HCC827 GR6) to gefitinib therapy and in two different NSCLC patient populations: 24 never smokers or EGFR FISH-positive patients treated with gefitinib (ONCOBELL cohort) and 182 surgically resected NSCLC not exposed to anti-EGFR agents.

RESULTS

HCC827 GR6-resistant cell line displayed MET amplification, with a mean MET copy number >12, while sensitive HCC827 cell line had a mean MET copy number of 4. In the ONCOBELL cohort, no patient had gene amplification and MET gene copy number was not associated with outcome to gefitinib therapy. Among the surgically resected patients, MET was amplified in 12 cases (7.3%) and only four (2.4%) had a higher MET copy number than the resistant HCC827 GR6 cell line.

CONCLUSIONS

MET gene amplification is a rare event in patients with advanced NSCLC. The development of anti-MET therapeutic strategies should be focused on patients with acquired EGFR-TKI resistance.

Primary resistance to cetuximab therapy in EGFR FISH-positive colorectal cancer patients

The impact of KRAS mutations on cetuximab sensitivity in epidermal growth factor receptor fluorescence in situ hybridisation-positive (EGFR FISH+) metastatic colorectal cancer patients (mCRC) has not been previously investigated. In the present study, we analysed KRAS, BRAF, PI3KCA, MET, and IGF1R in 85 mCRC treated with cetuximab-based therapy in whom EGFR status was known. KRAS mutations (52.5%) negatively affected response only in EGFR FISH+ patients. EGFR FISH+/KRAS mutated had a significantly lower response rate (P=0.04) than EGFR FISH+/KRAS wild type patients. Four EGFR FISH+ patients with KRAS mutations responded to cetuximab therapy. BRAF was mutated in 5.0% of patients and none responded to the therapy. PI3KCA mutations (17.7%) were not associated to cetuximab sensitivity. Patients overexpressing IGF1R (74.3%) had significantly longer survival than patients with low IGF1R expression (P=0.006), with no difference in response rate. IGF1R gene amplification was not detected, and only two (2.6%) patients, both responders, had MET gene amplification. In conclusion, KRAS mutations are associated with cetuximab failure in EGFR FISH+ mCRC, even if it does not preclude response. The rarity of MET and IGF1R gene amplification suggests a marginal role in primary resistance. The potential prognostic implication of IGF1R expression merits further evaluation.

Surrogate predictive biomarkers for response to anti-EGFR agents: state of the art and challenges

The epidermal growth factor receptor (EGFR) plays a key role in cancer development and progression in several human malignancies including non-small cell lung cancer (NSCLC). Several strategies aimed at inhibiting the EGFR have been investigated in the last years, including the use of small tyrosine kinase inhibitors (TKIs) directed against the intracellular domain of the receptor and monoclonal antibodies targeting its extracellular portion. Subgroups of patients who are more likely to respond to TKIs have been identified based on both clinical and biological features. Never-smoking history has emerged as the most relevant clinical characteristic predictive of response to TKIs in NSCLC, while presence of drug-sensitive EGFR mutations and EGFR gene gain represent critical biological variables associated with an improved outcome for patients exposed to these agents. Recent studies have highlighted the existence of biological factors involved in intrinsic and acquired resistance to TKIs, including k-ras, HER-2 and EGFR exon 20 mutations. Increasing knowledge of EGFR biology and drug-receptor interactions will allow to identify individuals who are likely to derive a clinical benefit from the proposed targeted therapy, sparing refractory patients expensive and potentially toxic treatment.

Protein-Structure-Based Prediction of Animal Model Suitability for Pharmacodynamic Studies of Subtype-Selective Estrogens

Subtype-selective estrogens are of increasing importance as tools used to unravel physiological roles of the estrogen receptors, ERalpha and ERbeta, in various species. Although human ERalpha and ERbeta differ by only two amino acids within the binding pockets, we and others recently succeeded in generating subtype-selective agonists. We have proposed that the selectivity of the steroidal compounds 16alpha-lactone-estradiol (16alpha-LE(2), hERalpha selective) and 8beta-vinyl-estradiol (8beta-VE(2), hERbeta selective) is based on the interaction of certain substituents of these compounds with essentially one amino acid in the respective ER binding pockets. For in vitro and ex vivo pharmacological experiments with these compounds we intended to use bovine tissues available from slaughterhouses in larger quantities. Using homology modeling techniques we determined that the amino acid conferring high hERbeta-selectivity to 8beta-VE(2) is not exchanged between human and bovine ERalpha and bovine ERbeta. Thus, we predicted our steroidal hERbeta-selective compound to exhibit only weak agonistic activity at bERbeta and that bovine tissue is therefore not suited for investigation of ERbeta functions. The situation is presumably identical for pig, sheep, and the common marmoset, whereas rats, mice, and rhesus macaques are appropriate animal models to study pharmacological effects of 8beta-VE(2) in vivo. This prediction was confirmed in transactivation studies assessing estradiol (E(2)) and the two subtype-selective ligands on bovine ERbeta and on a series of hERalpha and hERbeta with mutations in their respective ligand-binding pockets. We have shown that the detailed understanding of the interactions of a compound with its target protein enables the identification of relevant species for pharmacological studies.

EGFR, HER2, and phospho-Akt are not predictive factors for response to first-line chemotherapy in patients with advanced non-small cell lung cancer (NSCLC)

7111

Background: Response to Epidermal Growth Factor Receptor tyrosine kinase inhibitor (EGFR-TKI) therapy is significantly associated with increased EGFR gene copy number, increased EGFR expression or presence of activating EGFR gene mutations. In presence of EGFR, increased HER2 gene copy number, as well as activation of the anti-apoptotic protein Akt demonstrated to increase EGFR-TKI sensitivity in both clinical and preclinical models. Aim of the present study was to assess whether these biomarkers also associate with response to first-line chemotherapy. Methods: Patients with advanced NSCLC with full clinical data and with tumor tissue available were selected for this analysis. Specimens were evaluated for EGFR and HER2 gene copy number by FISH, EGFR and p-AKT protein expression by immunohistochemistry. RECIST criteria were used to assess response to chemotherapy. Results: A total of 144 NSCLC were included in this analysis. Patient characteristics included: male/female: 95/49; PS 0/1/2: 112/29/3; stage III/IV: 44/100; adenocarcinomas plus bronchioloalveolar/squamous/other: 86/35/23; never/former/current smokers: 26/69/49. The majority of patients were treated with first-line platinum-based chemotherapy (115/79.9%). Response to chemotherapy was not associated with any clinical characteristic. A trend towards better response was observed in non-adenocarcinoma histologies (p = 0.08) and in smokers (p = 0.20). Response and time to disease progression (TTP) were not influenced by EGFR/HER2 FISH status, nor P-Akt/EGFR expression. In EGFR FISH positive response rate was 36.4% and TTP was 6.4 months, versus 28.7% and 7.3 months in EGFR FISH negative (p = 0.4 for both). Conclusions: Biomarkers useful for selection of patients candidate for TKI therapy are not predictive for response to first-line chemotherapy in NSCLC.

No significant financial relationships to disclose.

Clinical and biological effects of gefitinib in EGFR FISH positive/phospho-akt positive or never smoker non-small cell lung cancer (NSCLC): Preliminary results of the ONCOBELL trial

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Background: Effectiveness of gefitinib, a tyrosine kinase inhibitor of the epidermal growth factor receptor (EGFR), in never smokers and/or EGFR FISH positive NSCLC patients has been evaluated only in retrospective studies and few data exist on the biological effects of gefitinib therapy in tumor samples. Methods: The ONCOBELL trial is a multicenter prospective phase II study designed to include 39 patients EGFR FISH positive/phospho-Akt (p-AKT) positive and/or never smokers with advanced or metastatic NSCLC. Gefitinib is given at the daily dose of 250 mg. When feasible, primary tumor biopsy was repeated immediately before therapy, during therapy and at progression. Specimens were evaluated for EGFR and HER2 gene copy number by FISH, EGFR gene mutation by DNA sequencing, and EGFR and p-AKT protein expression by immunohistochemistry. Results: Data from the first 28 enrolled patients are available: median age was 60 years (range, 43–80); male/female: 7/21; stage IIIB/IV: 2/26; ECOG PS 0/1/2: 18/6/4; 25 patients had a diagnosis of adenocarcinoma and/or bronchioloalveolar carcinoma; 13 patients had brain metastases, and in 10 cases gefitinib was offered as first-line therapy. Twenty-four patients were never smokers and 19 were EGFR FISH positive. Overall response rate was 54%, including 1 complete and 14 partial responses. Median time to progression was 6.45 months, and median survival was not reached. Response to therapy was not influenced by previous therapies or presence of brain metastases. Toxicity was mild, and consisted in grade 1–2 skin rash (68%) and diarrhea (57%). One patient developed grade 3 diarrhea and another patient was hospitalized for acute interstitial lung disease. In patients exposed to previous chemotherapy, no difference in EGFR or HER2 FISH results were observed in specimens collected at the time of original diagnosis compared to specimens collected immediately before gefitinib therapy. In 14 cases primary tumor biopsy was repeated during gefitinib therapy. Conclusions: These preliminary data indicate that gefitinib is highly effective in patients with trial characteristics. Clinical and biological data for the entire cohort will be available in June 2006.

No significant financial relationships to disclose.

Role of gemcitabine in cancer therapy

Gemcitabine, a pyrimidine nucleoside antimetabolite, is one of the most promising new cytotoxic agents. The drug has shown activity in a variety of solid tumors, and has been approved for the treatment of non-small cell lung cancer, pancreatic, bladder, and breast cancer. Recent data showed that gemcitabine is also active against ovarian cancer. Gemcitabine has a good toxicity profile, with myelosuppression being the most common side effect, while non-hematological events are relatively uncommon. The low toxicity profile makes the drug a valid option for unfit and elderly patients. Due to the synergistic activity with other chemotherapeutic compounds, mainly cisplatinum, several trials have been conducted to evaluate the efficacy and tolerability of gemcitabine in combination with other cytotoxic agents. Current clinical trials are evaluating the role of gemcitabine in combination with new targeted therapies.

Development of gemcitabine in non-small cell lung cancer: the Italian contribution

Gemcitabine, a pyrimidine nucleoside antimetabolite, is one of the most promising new cytotoxic agents. The drug has shown activity in a variety of solid tumors, but appears to be most active in the treatment of non-small cell lung cancer. In this disease, several Italian investigators have evaluated gemcitabine in phase II and III clinical trials. Due to preclinical synergism with cisplatin, the Italian Lung Cancer Project played an important role to assess the efficacy and activity of the gemcitabine-cisplatin combination along with the best doses and schedule to adopt, thus leading to gemcitabine approval for first line treatment of advanced non-small cell lung cancer. Several Italian studies have also investigated gemcitabine non-platinum based combinations, gemcitabine in third generation platinum-based triplets and gemcitabine as second line therapy, but all these studies led to conflicting and inconclusive results. The low toxicity profile makes the drug a valid option for unfit and elderly patients. The Multicenter Italian Lung Cancer in the Elderly Study was a phase III randomized trial conducted in elderly patients with advanced non-small cell lung cancer that showed that single agent gemcitabine is at least as effective as either single agent vinorelbine or the combination of gemcitabine and vinorelbine. In the neoadjuvant treatment of stage III disease, a number of phase II studies with third generation platinum-based doublets or triplets have been conducted by Italian investigators with encouraging results. Current clinical trials are addressing the role of gemcitabine in combination with new targeted therapies. Future studies should be designed in order to identify subgroups of patients who are more likely to benefit from gemcitabine chemotherapy.

Insulin-like growth factor receptor 1 (IGFR-1) is significantly associated with longer survival in non-small-cell lung cancer patients treated with gefitinib

BACKGROUND

The aim of the study was to assess whether loss of PTEN and expression of insulin-like growth factor receptor 1 (IGFR-1) could be responsible for intrinsic resistance to the tyrosine kinase inhibitor (TKI) gefitinib.

PATIENTS AND METHODS

One hundred and twenty-four gefitinib-treated patients with advanced non-small-cell lung cancer (NSCLC) were analyzed for PTEN and IGFR-1 expression by immunohistochemistry.

RESULTS

IGFR-1 was evaluated in 77 patients and resulted positive in 30 (39.0%). IGFR-1 expression was not significantly associated with clinical or biological characteristics. No difference in response to gefitinib treatment (16.7% versus 12.8%, P = 0.74) and time to progression (2.6 versus 3.06 months, P = 0.83) was observed between IGFR-1+ and IGFR-1-. Median survival was significantly longer in IGFR-1+ patients (17.8 versus 7.3 months, P = 0.013). PTEN expression was successfully evaluated in 93 cases. Loss of PTEN was detected in 19 tumors (20.4%) and was not associated with any clinical or biological characteristic. No difference in terms of response, time to progression and survival was observed between PTEN+ and PTEN- patients. In multivariable analysis IGFR-1 negative status was significantly associated with higher risk of death (hazard ratio 2.21, P = 0.012).

CONCLUSIONS

IGFR-1 expression and loss of PTEN are not associated with intrinsic resistance to gefitinib. Clinical relevance of these two biomarkers as determinant for acquired resistance, and the prognostic role of IGFR-1 expression in patients not exposed to TKIs should be evaluated further.

HER3 genomic gain and sensitivity to gefitinib in advanced non-small-cell lung cancer patients

In non-small-cell lung cancer (NSCLC), sensitivity to tyrosine kinase inhibitors (TKIs) is associated with activating mutations and genomic gain of the epidermal growth factor receptor (EGFR). Preclinical data suggested that HER3 overexpression increases sensitivity to TKIs. A total of 82 NSCLC patients treated with gefitinib (250 mg), and previously evaluated for EGFR and HER2 status by fluorescence in situ hybridisation (FISH) and DNA sequencing, and for Phospho-Akt status by immunohistochemistry, were investigated for HER3 genomic gain by FISH. Patients with high polysomy and gene amplification were considered as HER3 FISH positive (+). HER3 FISH+ pattern was significantly associated with female gender (P=0.02) and never smoking history (P=0.02). Patients with HER3+ tumours (26.8%) had a significantly longer time to progression (3.7 vs 2.7, P=0.04) than patients with HER3− tumours, but not a significantly better response rate or survival. Patients with EGFR+/HER3+ tumours had higher objective response rate (36.4 vs 9.9%, P=0.03) and time to progression (7.7 vs 2.7 months, P=0.03) than patients with EGFR− and/or HER3− tumours, but no significantly longer survival. No difference in response was observed according to HER3 status in patients with EGFR+ tumours. Patients with HER2+/HER3+ tumours had similar outcome as patients with HER2− and/or HER3− tumours. Significantly different clinical end points were not observed between patients with HER3+/P-Akt+ and HER3− and/or P-Akt− tumours. Genomic gain for HER3 is not a marker for response or resistance to TKI therapy in advanced NSCLC patients.

LRRK1 protein kinase activity is stimulated upon binding of GTP to its Roc domain

Human leucine-rich repeat kinase 1 (LRRK1) is a multi-domain protein of unknown function belonging to the ROCO family of complex proteins. Here, we report the molecular characterization of human LRRK1 and show, for the first time, that LRRK1 is both a functional protein kinase and a GDP/GTP-binding protein. Binding of GTP to LRRK1 is specific, requires the GTPase-like Roc domain, and leads to a stimulation of LRRK1 kinase activity. LRRK1 is the first example of a GTP-regulated protein kinase harboring both the kinase effector domain and the GTP-binding regulatory domain. Hence, we propose a model in which LRRK1 cycles between a GTP-bound active and a GDP-bound inactive state. Moreover, we mutated LRRK1 to mimic mutations previously identified in LRRK2/dardarin, the only human paralogue of LRRK1, that have been linked to autosomal-dominant parkinsonism. We demonstrate that three of four mutations analyzed significantly downregulate LRRK1 kinase activity. Ultimately, the results presented for LRRK1 may contribute to the elucidation of LRRK2's role in the pathogenesis of Parkinson's disease.

Efficacy and tolerability of gefitinib in pretreated elderly patients with advanced non-small-cell lung cancer (NSCLC)

The activity and toxicity profile of gefitinib in non-small cell lung cancer (NSCLC) patients aged 70 years or older has been only partially evaluated. The aim of this study was to evaluate the response rate and safety of gefitinib in elderly NSCLC patients. Elderly NSCLC patients pretreated with chemotherapy and with at least one measurable lesion received gefitinib at the daily dose of 250 mg until disease progression, unacceptable toxicity or refusal. From August 2001 to May 2003, 40 consecutive elderly patients have been enrolled onto the study in three Italian institutions. We observed one complete (2.5%) and one partial response (2.5%), 18 disease stabilisations (NC: 45%) lasting at least 2 months, including six patients (15%) who had disease stabilisation of 6 months or longer, for an overall disease control rate of 50% (95% CI: 34.5-65.5%). The median duration of response was 4.4 months (range 1.7-9.2). The side effects were generally mild and consisted of diarrhoea and skin toxicity. Grade 1-2 diarrhoea occurred in 23.6%, and one patient experienced grade 4 diarrhoea, requiring hospitalisation. Grade 1-2 skin toxicity, including rash, pruritus, dry skin, and acne, occurred in 20 patients (52.6%). Gefitinib is safe and well tolerated in elderly pretreated NSCLC patients. The disease-control rate achieved suggests that this drug could represent a valid option in the management of this unfavourable subgroup of patients.

A novel, soluble homologue of the human IL-10 receptor with preferential expression in placenta

The cytokine receptor family type 2 (CRF2) comprises receptors for important immunomediators like interferons and interleukin-10 (IL-10). We identified a novel member of this family which represents the first exclusively soluble receptor in this group and was therefore designated as CRF2-soluble 1 (CRF2-s1). The CRF2-s1 gene covers about 28 kb and is located on chromosome 6 in close proximity to the CRF2 members interferon (IFN)-gamma receptor 1 and IL-20 receptor 1. It comprises seven exons and generates two different mRNA splice variants, CRF2-s1-long and CRF2-s1-short. CRF2-s1-long and CRF2-s1-short encode proteins of 263 and 231 amino acids, respectively. A comparison of predicted protein structures led to the postulation that each receptor variants binds a different ligand. Quantitative analysis of human mRNA expression revealed a very restricted pattern for both splice forms. CRF2-s1 turned out to be the first member of this receptor family which was expressed neither in resting nor in stimulated leucocyte populations. CRF2-s1-long was only expressed in placenta, whereas CRF2-s1-short was additionally expressed in human mammary gland and, at a lower level, in skin, spleen, thymus and stomach. The preferential expression of CRF2-s1 in placenta suggests a role for this receptor in establishing and maintaining successful pregnancy.

Fibrin selectivity of the isolated protease domains of tissue-type and vampire bat salivary gland plasminogen activators

The activity of vampire bat (Desmodus rotundus) salivary plasminogen activator (D. rotundus PA alpha1) and to a much lesser extent of tissue-type plasminogen activator (t-PA) is stimulated by the presence of fibrin. This cofactor requirement has in the past intuitively been attributed to fibrin binding. We have previously shown that elements of the non-protease domain of D. rotundus PA alpha1 could contribute to fibrin stimulation irrespective of fibrin binding. We now demonstrate that the protease domain of D. rotundus PA alpha1 by itself exhibits fibrin selectivity, i.e. it is 32-fold stimulated by fibrin but only 1.5-fold by fibrinogen. To a lesser extent this fibrin selectivity is also shared by the protease domain of t-PA. Our findings indicate that protein-protein interactions apart from fibrin binding affect the stimulatory mechanism of fibrin on D. rotundus PA alpha1 and t-PA.

Structural features mediating fibrin selectivity of vampire bat plasminogen activators

The distinguishing characteristic of vampire bat (Desmodus rotundus) salivary plasminogen activators (DSPAs) is their strict requirement for fibrin as a cofactor. DSPAs consist of structural modules known from urokinase (u-PA) and tissue-type plasminogen activator (t-PA) such as finger (F), epidermal growth factor (E), kringle (K), and protease (P), combining to four genetically and biochemically distinct isoenzymes, exhibiting the formulas FEKP (DSPA alpha 1 and alpha 2) and EKP and KP (DSPA beta and DSPA gamma). Only DSPA alpha 1 and alpha 2 bind to fibrin. All DSPAs are single-chain molecules, displaying substantial amidolytic activity. In a plasminogen activation assay, all four DSPAs are almost inactive in the absence of fibrin but strongly stimulated by fibrin addition. The catalytic efficiency (kcat/Km) of DSPA alpha 1 increases 10(5)-fold, whereas the corresponding value of t-PA is only 550. The ratio of the bimolecular rate constants of plasminogen activation in the presence of fibrin versus fibrinogen (fibrin selectivity) of DSPA alpha 1, alpha 2, beta, gamma, and t-PA was found to be 13,000, 6500, 250, 90, and 72, respectively. Whereas all DSPAs are therefore more fibrin dependent and fibrin selective than t-PA, the extent depends on the respective presence of the various domains. The introduction of a plasmin-sensitive cleavage site in a position akin to the one in t-PA partially obliterates fibrin cofactor requirement. Fibrin dependence and fibrin selectivity of DSPAs are accordingly mediated by fibrin binding, which involves the F domain, as yet undefined determinants within the K and P domains, and by the absence of a plasmin-sensitive activation site. These findings transcend the current understanding of fibrin-mediated stimulation of plasminogen activation: in addition to fibrin binding, specific protein-protein interactions come into play, which stabilize the enzyme in its active conformation.

Low-M(r) urokinase-type plasminogen activator as a reporter protein

A reporter plasmid coding for the low-molecular-weight (low-M(r)) form of single-chain urokinase-type plasminogen activator (low-M(r) u-PA; Leu144-Leu411) has been constructed and used to analyze promoter activity. Vectors containing the low-M(r) u-PA cDNA coupled to hormone-responsive promoters were introduced to mammalian cells. Following hormone treatment, the activity of the secreted reporter protein was determined in aliquots of cell culture supernatants. The assay is based on plasminogen activation by low-M(r) u-PA and subsequent cleavage of the plasmin-specific tripeptide substrate, S-2251. The resulting chromophore, p-nitroanilide, was quantified colorimetrically at 405 nm. Transient and stable expression of the low-M(r) u-PA reporter gene in different eukaryotic cells demonstrates the suitability of the system for the quantification of the activity of eukaryotic promoter elements in a rapid and highly sensitive manner, while maintaining cell integrity.

Distribution of neurotransmitters, neuropeptides, and receptors in the vestibular nuclei complex of the rat: an immunocytochemical, in situ hybridization and quantitative receptor autoradiographic study

This article investigates the distribution of neurotransmitters, neuropeptides, and related receptors in the vestibular nuclei complex (VNC) of the adult rat by means of immunohistochemistry, in situ hybridization, and quantitative receptor autoradiography. The entire complex proves to be rich in muscarinic receptors and it shows a high density of imipramine and benzodiazepine binding sites. Peptidergic neurons and a few positive fibers are described in the caudal part of the VNC. In particular, the medial vestibular nucleus contains a number of neurons expressing both the enkephalin mRNA and peptide. This nucleus and the lateral vestibular nucleus are also rich in opiate receptors. Substance P, thyrotropin releasing hormone, and neurotensin receptors are also found in the medial and in the spinal vestibular nuclei. In spite of the presence of alpha 2 catecholaminergic receptors, no thyrosine-hydroxylase-immuno-reactive elements are seen in the caudal VNC. The possible functional meaning of these data is discussed.

The product of a novel growth factor activated gene, fos B, interacts with JUN proteins enhancing their DNA binding activity

We have identified a gene, fos B, encoding a nuclear protein of 338 amino acids presenting a 70% homology with c-fos, whose expression is activated during G0/G1 transition. Growth factor stimulation of quiescent cells leads to a rapid and transient accumulation of fos B mRNA, with kinetics similar to those of c-fos. The induction of fos B mRNA levels is in part due to a dramatic increase in the transcription of the gene. The half-life of fos B mRNA is in the order of 10-15 min. Both transcriptional activation and mRNA stability are substantially increased in the presence of protein synthesis inhibitors. Immunoprecipitation studies showed that fos B as c-fos protein, forms a complex in vitro with c-jun and jun B proteins in the absence of a target binding sequence. Gel retardation assays demonstrated that fos B protein positively influences the binding of c-jun and jun B proteins to an AP-1 binding consensus sequence, suggesting that fos B protein plays a role in control of gene expression.

Changes in cyclin/proliferating cell nuclear antigen distribution during DNA repair synthesis

UV irradiation of quiescent human fibroblasts immediately triggers the appearance of the nuclear protein cyclin/proliferating cell nuclear antigen (PCNA) as detected by indirect immunofluorescent staining after methanol fixation. This was found to be independent of new synthesis of cyclin/PCNA by two-dimensional gel analysis and cycloheximide treatment. The intensity of the immunofluorescent staining of cyclin/PCNA observed in UV-irradiated cells corresponded with the UV dose used and with the DNA repair synthesis detected by autoradiography. The nuclear staining remains as long as DNA repair activity is detected in the cells. By extracting the UV-irradiated quiescent cells with Triton X-100 and fixing with formaldehyde, it was possible to demonstrate by indirect immunofluorescence rapid changes in the cyclin/PCNA population after irradiation, a small proportion (5-10%) of which is tightly associated to the nucleus as determined by high salt extraction. By incubating at low temperature and depleting the ATP pools of the cells before UV irradiation, we have demonstrated that the changes in cyclin/PCNA distribution observed involve at least two different nuclear associations.

Effect of the growth conditions on the expression of cell-surface-associated platelet-derived growth factor receptors in mouse fibroblasts

The conditions affecting the appearance and disappearance of platelet-derived growth factor (PDGF) receptors from the pool of active cell surface-associated receptors were studied. Receptor molecules were revealed in intact Swiss 3T3 fibroblasts by their ability to bind 125I-labeled PDGF and, due to their property to become phosphorylated in tyrosine following ligand binding, by antibodies to phosphotyrosine. PDGF receptor molecules were found to be quite scarce in exponentially growing fibroblasts as compared to quiescent cells. When growing cells were either shifted to a medium containing plasma or received suramin in the culture medium, cell surface-associated PDGF receptors largely increased. This process required about 12 h. Incubation of quiescent cells in serum, but not in plasma, induced a slow decrement of ligand-activatable receptors. In the presence of PDGF the rate of receptor removal from the cell surface was very rapid and was a function of the PDGF concentration. Quiescent cells deprived of cell-surface receptors by incubation with PDGF reexpressed PDGF receptors in about 14 h.