Transforming growth factor alpha expression drives constitutive epidermal growth factor receptor pathway activation and sensitivity to gefitinib (Iressa) in human pancreatic cancer cell lines

Tetrahydrobenzothiophene derivatives ameliorate Mia PaCa-2 cell progression and induces apoptosis via inhibiting EGFR2 tyrosine kinase signal

A series of new thiophene analogues with acarbonitrile-basedmoiety were designed and synthesized via structural optimization. The conjugates were assessed for their in-vitro cytotoxic activity against a human pancreatic cancer cell line (Mia PaCa-2) and among them compound 5b showed IC50 value of 13.37 ± 2.37 μM. The compounds 5b (20 µM & 25 µM) and 7c (30 & 35 µM) also showed reduced clonogenicity, enhanced ROS and decreased mitochondrial membrane potential in Mia PaCa-2 cells. Treatment with these compounds also increased apoptotic population as evident with the double staining assay. Among the evaluated series, compounds 5b, 5g, 7c, and 9a attained a greater inhibitory potency than first generation's reversible EGFR inhibitor, Gefitinib. EGFR2 enzyme inhibitory studies revealed that 5b efficiently and arbitrarily suppressed the development of EGFR2 dependent cells and inhibited the enzymatic activity with an IC50 value of 0.68 µM; interestingly, the most effective molecule 5b with N-methyl piperazine substitution, has 1.29-fold greater potency than well-known EGFR inhibitor Gefitinib and increased Gefitinib's anti-growth impact with 2.04 folds greater against Mia PaCa-2. The in-vitro studies were validated with in-silico docking studies wherein compounds 5b and 7c exhibited binding energies of -8.2 and -7.4 Kcal/mol respectively. The present study reveals that tetrahydrobenzothiophene based analogues could be a promising lead for the evolution of potent chemo preventives over pancreatic cancer.

MiR-338-5p Inhibits EGF-Induced EMT in Pancreatic Cancer Cells by Targeting EGFR/ERK Signaling

The epidermal growth factor (EGF) pathway plays critical roles during cancer cell epithelial-mesenchymal transition (EMT) process and metastasis. Epidermal growth factor receptor (EGFR), as one of the important receptors of EGF, undergoes autophosphorylation with the stimulation of EGF and activates MAPK/ERK, PI3K/Akt/mTOR, and other pathways. Here, we identified EGFR was a target of miR-338-5p. Upon EGF treatment, overexpression of miR-338-5p not only downregulated EGFR expression and inhibited MAPK/ERK signaling, but also inhibited EMT and metastasis process of pancreatic cancer (PC) cells. In the clinical pathological analysis, miR-338-5p was significantly down-regulated in 44 pairs PC tissues and its expression was negatively associated with lymph node metastasis and AJCC stage. Furthermore, Overexpression of EGFR partially reversed the protective effect of miR-338-5p overexpression on EGF-mediated migration and invasion in PC cells. Taken together, miR-338-5p controls EGF-mediated EMT and metastasis in PC cells by targeting EGFR/ERK pathways. Here, we hope to provide new insights into the molecular mechanisms of pancreatic cancer, and may help facilitating development of EGFR-based therapies for human cancer.

Refined construction of antibody-targeted nanoparticles leads to superior antigen binding and enhanced delivery of an entrapped payload to pancreatic cancer cells

Antibody-targeted nanoparticles have shown exceptional promise as delivery vehicles for anticancer drugs, although manufacturability challenges have hampered clinical progress. These include the potential for uncontrolled and random antibody conjugation, resulting in masked or inactive paratopes and unwanted Fc domain interactions. To circumvent these issues, we show that the interchain disulfide of cetuximab F(ab) may be selectively re-bridged with a strained alkyne handle, to permit 'click' coupling to azide-capped nanoparticles in a highly uniform and oriented manner. When compared to conventional carbodiimide chemistry, this conjugation approach leads to the generation of nanoparticles with a higher surface loading of cetuximab F(ab) and with markedly improved ability to bind to the target epidermal growth factor receptor. Moreover, we show that entrapment of a camptothecin payload within these nanoparticles can enhance drug targeting to antigen-expressing pancreatic cancer cells, resulting in superior cytotoxicity versus the conventional nanoformulation. Collectively, this work highlights the critical need to develop refined methods for the construction of targeted nanoparticles that will accelerate their clinical translation through improved performance and manufacturability.

Overexpression of EGFR and TGFα in von Hippel-Lindau-Related Central Nervous System Hemangioblastomas

Background: Central nervous system (CNS) hemangioblastomas (HGBs) are the most frequent cause of mortality in patients with von Hippel–Lindau (VHL) disease. Characteristics of multiple and recurrent disease cause certain difficulties in the treatment of CNS HGBs.

Methods: VHL-related HGB cases treated surgically at our hospital from September 2015 to February 2019 were analyzed. Patients meeting the clinical diagnostic criteria underwent genetic testing. Real-time PCR and immunohistochemistry were used in HGBs to verify differential expression of mRNAs and proteins, respectively. Furthermore, correlations between the differentially expressed proteins and the histological grading, genetic mutations, and tumor burden were also analyzed.

Results: A total of 21 patients with VHL syndrome confirmed by genetic testing (missense group, 9; partial deletion group, 12) were enrolled, and 30 CNS HGBs from these patients were studied. Clinical data showed that men at first operation were significantly younger than females (p = 0.005). Real-time PCR demonstrated that EGFR (p = 0.017) and TGFα (p = 0.017) mRNA expression in VHL-related HGBs was significantly higher than that in the control group. Immunohistochemistry showed that the mean optical density in VHL-related HGBs was significantly higher than that in controls (EGFR, p = 0.007; TGFα, p = 0.021). Finally, the cyst volume was related to the upregulation of EGFR (r = 0.782, p < 0.01).

Conclusion: Overexpression of EGFR and TGFα may contribute to tumor growth in VHL-related CNS HGBs. The cyst volume was associated with EGFR overexpression. These results provide information for the management of VHL-related HGBs in the era of targeted therapeutics.

Berbamine Enhances the Efficacy of Gefitinib by Suppressing STAT3 Signaling in Pancreatic Cancer Cells

Background

Small molecular inhibitors such as gefitinib (Gefi), which target EGF receptor (EGFR), are considered to be a viable pathway for the selective inhibition of pancreatic cancer (PC) development. However, the large difference in Gefi response between PC patient individuals and PC cell lines severely limits the clinical efficacy of Gefi. Berbamine (BBM) is a well-known natural-derived antitumor agent. However, no study yet exists on whether BBM can enhance the sensitivity of PC cells to Gefi or its underlying mechanisms.

Methods

MTS assay and clonogenic assay were used to determine whether BBM could enhance the anti-PC activity of Gefi by. Flow cytometric analysis was performed to study the cell cycle progression and rate of apoptosis after combined treatment with BBM and Gefi. Surface plasmon resonance (SPR) and Western blot experiments were carried out to detect the STAT3 binding affinity and the STAT3 inhibitory effect of BBM. Molecular docking and Molecular dynamic simulation were used to predicting the dominant interaction between BBM and STAT3.

Results

This study found that BBM synergizes with Gefi to inhibit cell growth and induce cell cycle arrest and PC cell apoptosis. Mechanistically, our results showed that BBM and Gefi have synergistic inhibitory effects on STAT3 phosphorylation, but have little effect on other EGFR downstream pathways, suggesting that BBM may exert sensitization through the inhibition of STAT3. Besides, BBM has a high affinity for STAT3 and a good inhibitory effect on STAT3 activation, further indicating that BBM was a potent direct STAT3 inhibitor. Molecular modeling between STAT3 and BBM suggested that BBM formed several key hydrophilic interactions with STAT3.

Conclusion

Our findings suggest that the combination of BBM and Gefi could be further developed as a potential PC therapy.

Mesothelin and TGF-α predict pancreatic cancer cell sensitivity to EGFR inhibitors and effective combination treatment with trametinib

Clinical trials of EGFR inhibitors in combination with gemcitabine for the treatment of pancreatic ductal adenocarcinoma (PDAC) have generated mixed results partially due to the poorly defined effectiveness of EGFR inhibitors in PDAC. Here, we studied a panel of PDAC cell lines to compare the IC50s of the EGFR inhibitors gefitinib and cetuximab. We found that gefitinib induced biphasic inhibition in over 50% of PDAC cells, with the initial growth inhibition occurring at nanomolar concentrations and a second growth inhibition occurring outside the clinical range. In contrast to gefitinib, cetuximab produced a single phase growth inhibition in a subset of PDAC cells. Using this sensitivity data, we screened for correlations between cell morphology proteins and EGFR ligands to EGFR inhibitor sensitivity, and found that mesothelin and the EGFR ligand TGF-α have a strong correlation to gefitinib and cetuximab sensitivity. Analysis of downstream signaling pathways indicated that plc-γ1 and c-myc were consistently inhibited by EGFR inhibitor treatment in sensitive cell lines. While an inconsistent additive effect was observed with either cetuximab or gefitinib in combination with gemcitabine, the cell pathway data indicated consistent ERK activation, leading us to pursue EGFR inhibitors in combination with trametinib, a MEK1/2 inhibitor. Both cetuximab and gefitinib in combination with trametinib produced an additive effect in all EGFR sensitive cell lines. Our results indicate that mesothelin and TGF-α can predict PDAC sensitivity to EGFR inhibitors and a combination of EGFR inhibitors with trametinib could be a novel effective treatment for PDAC.

Antitumor Effect of Various Phytochemicals on Diverse Types of Thyroid Cancers

Thyroid cancers developed from the tissues of the thyroid gland are classified into papillary (PTC), follicular (FTC), medullary (MTC), and anaplastic thyroid cancer (ATC). Although thyroid cancers have been generally known as mild forms of cancer, undifferentiated MTC and ATC have a more unfavorable prognosis than differentiated PTC and FTC because they are more aggressive and early metastatic. A variety of therapies such as surgery, radiotherapy, and chemotherapy have been currently used to treat thyroid cancer, but they still have limitations including drug resistance or unfavorable side effects. Phytochemicals are plant-derived chemicals having various physiological activities that are expected to be effective in cancer treatment. In this review, anticancer efficacy of phytochemicals, such as resveratrol, genistein, curcumin, and other substances in each type of thyroid cancer was introduced with their chemopreventive mechanisms. English articles related with thyroid cancer and anti-thyroid cancer of phytochemicals were searched from PubMed and Google Scholar. This article mainly focused on in vitro or animal studies on phytochemicals with anti-thyroid cancer activity. These various phytochemicals have been shown to induce apoptosis in all types of thyroid cancer cells, inhibit cell proliferation and invasion, and to be helpful in enhancing the effect of radioiodine therapy that is a typical therapy to thyroid cancer. These results suggest that thyroid cancer can be more effectively treated by the combinations of phytochemicals and the existing therapies or substances.

A Retrospective Look at Anti-EGFR Agents in Pancreatic Cancer Therapy

BACKGROUND

The introduction of Monoclonal Antibodies (mAbs) and small-molecule Tyrosine Kinase Inhibitors (TKIs) that target the Epidermal Growth Factor Receptor (EGFR), marks a huge step forward in the Pancreatic Cancer (PC) therapy. However, anti-EGFR therapy is found to be successful only in a fraction of patients. Although anti-EGFR agents have shown considerable clinical promise, a serious adverse event associated with anti- EGFR therapy has been challenging. At this juncture, there is still more to be done in the search for effective predictive markers with therapeutic applicability.

METHODS

A focused literature search was conducted to summarize the existing evidence on anti-EGFR agents in pancreatic cancer therapy.

RESULTS

This review discusses various anti-EGFR agents currently in use for PC therapy and potential adverse effects associated with it. Existing evidence on EGFR TKIs demonstrated better tolerant effects and outcomes with multiple toxic regimens. Anti-EGFR therapy in combination with chemotherapy is necessary to achieve the best clinical outcomes.

CONCLUSION

Future prospective studies on the identification of additional biological agents and novel anti-EGFR agents are warranted.

Targeting retinoblastoma protein phosphorylation in combination with EGFR inhibition in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) remains a particularly lethal disease that is resistant to targeted therapies. Tyrosine kinase inhibitors (TKIs), including erlotinib and gefitinib, which block the action of the human epidermal growth factor receptor type 1 receptor, provide small increases in patient survival when administered with gemcitabine. The retinoblastoma (Rb) tumor suppressor protein is an additional target in pancreatic cancer, due to its documented inactivation in PDAC. The present study, using cell number, apoptosis and immunoblotting assays, aimed to evaluate the effects of activation of the Rb tumor suppressor via dephosphorylation by small interfering RNA-mediated phosphatase activation. In the Panc1, MIAPaCa-2 and Capan-2 pancreatic cancer cell lines, and in normal H6c7 cells, the effects of phosphatase activation on Rb were revealed to be dependent on expression of the p16 tumor suppressor, which regulates Rb phosphorylation. Phosphatase activation had no effect on non-transformed pancreatic epithelial cells. When comparing kinase inhibition with phosphatase activation, it was demonstrated that kinase inhibition reduced proliferation, whereas phosphatase activation induced apoptosis. Both treatments together resulted in a greater reduction of pancreatic cancer cells than either treatment alone. In addition, the effects of combination treatment of phosphatase activation with TKIs on cell number and activation of the signal transducer and activator of transcription 3 (STAT3) resistance pathway were determined. The combination of Rb phosphatase activation with TKIs resulted in a greater reduction in cell number compared with either treatment alone, without STAT3 pathway activation. These data suggested that targeting Rb phosphorylation by activating phosphatase may be a rational strategy to inhibit pancreatic tumor cell growth, without activation of acquired resistance.

PRAS40 Connects Microenvironmental Stress Signaling to Exosome-Mediated Secretion

Secreted exosomes carrying lipids, proteins, and nucleic acids conduct cell-cell communications within the microenvironment of both physiological and pathological conditions. Exosome secretion is triggered by extracellular or intracellular stress signals. Little is known, however, about the signal transduction between stress cues and exosome secretion. To identify the linker protein, we took advantage of a unique finding in human keratinocytes. In these cells, although transforming growth factor alpha (TGF-α) and epidermal growth factor (EGF) share the same EGF receptor and previously indistinguishable intracellular signaling networks, only TGF-α stimulation causes exosome-mediated secretion. However, deduction of EGF-activated pathways from TGFα-activated pathways in the same cells allowed us to identify the proline-rich Akt substrate of 40 kDa (PRAS40) as the unique downstream effector of TGF-α but not EGF signaling via threonine 308-phosphorylated Akt. PRAS40 knockdown (KD) or PRAS40 dominant-negative (DN) mutant overexpression blocks not only TGF-α- but also hypoxia- and H₂O₂-induced exosome secretion in a variety of normal and tumor cells. Site-directed mutagenesis and gene rescue studies show that Akt-mediated activation of PRAS40 via threonine 246 phosphorylation is both necessary and sufficient to cause exosome secretion without affecting the endoplasmic reticulum/Golgi pathway. Identification of PRAS40 as a linker protein paves the way for understanding how stress regulates exosome secretion under pathophysiological conditions.

Focal Adhesion Kinase Inhibitors in Combination with Erlotinib Demonstrate Enhanced Anti-Tumor Activity in Non-Small Cell Lung Cancer

Blockade of epidermal growth factor receptor (EGFR) activity has been a primary therapeutic target for non-small cell lung cancers (NSCLC). As patients with wild-type EGFR have demonstrated only modest benefit from EGFR tyrosine kinase inhibitors (TKIs), there is a need for additional therapeutic approaches in patients with wild-type EGFR. As a key component of downstream integrin signalling and known receptor cross-talk with EGFR, we hypothesized that targeting focal adhesion kinase (FAK) activity, which has also been shown to correlate with aggressive stage in NSCLC, would lead to enhanced activity of EGFR TKIs. As such, EGFR TKI-resistant NSCLC cells (A549, H1299, H1975) were treated with the EGFR TKI erlotinib and FAK inhibitors (PF-573,228 or PF-562,271) both as single agents and in combination. We determined cell viability, apoptosis and 3-dimensional growth in vitro and assessed tumor growth in vivo. Treatment of EGFR TKI-resistant NSCLC cells with FAK inhibitor alone effectively inhibited cell viability in all cell lines tested; however, its use in combination with the EGFR TKI erlotinib was more effective at reducing cell viability than either treatment alone when tested in both 2- and 3-dimensional assays in vitro, with enhanced benefit seen in A549 cells. This increased efficacy may be due in part to the observed inhibition of Akt phosphorylation when the drugs were used in combination, where again A549 cells demonstrated the most inhibition following treatment with the drug combination. Combining erlotinib with FAK inhibitor was also potent in vivo as evidenced by reduced tumor growth in the A549 mouse xenograft model. We further ascertained that the enhanced sensitivity was irrespective of the LKB1 mutational status. In summary, we demonstrate the effectiveness of combining erlotinib and FAK inhibitors for use in known EGFR wild-type, EGFR TKI resistant cells, with the potential that a subset of cell types, which includes A549, could be particularly sensitive to this combination treatment. As such, further evaluation of this combination therapy is warranted and could prove to be an effective therapeutic approach for patients with inherent EGFR TKI-resistant NSCLC.

Transforming growth factor alpha is a critical mediator of radiation lung injury

Radiation fibrosis of the lung is a late toxicity of thoracic irradiation. Epidermal growth factor (EGF) signaling has previously been implicated in radiation lung injury. We hypothesized that TGF-α, an EGF receptor ligand, plays a key role in radiation-induced fibrosis in lung. Mice deficient in transforming growth factor (TGF-α(-/-)) and control C57Bl/6J (C57-WT) mice were exposed to thoracic irradiation in 5 daily fractions of 6 Gy. Cohorts of mice were followed for survival (n ≥ 5 per group) and tissue collection (n = 3 per strain and time point). Collagen accumulation in irradiated lungs was assessed by Masson's trichrome staining and analysis of hydroxyproline content. Cytokine levels in lung tissue were assessed with ELISA. The effects of TGF-α on pneumocyte and fibroblast proliferation and collagen production were analyzed in vitro. Lysyl oxidase (LOX) expression and activity were measured in vitro and in vivo. Irradiated C57-WT mice had a median survival of 24.4 weeks compared to 48.2 weeks for irradiated TGF-α(-/-) mice (P = 0.001). At 20 weeks after irradiation, hydroxyproline content was markedly increased in C57-WT mice exposed to radiation compared to TGF-α(-/-) mice exposed to radiation or unirradiated C57-WT mice (63.0, 30.5 and 37.6 μg/lung, respectively, P = 0.01). C57-WT mice exposed to radiation had dense foci of subpleural fibrosis at 20 weeks after exposure, whereas the lungs of irradiated TGF-α (-/-) mice were largely devoid of fibrotic foci. Lung tissue concentrations of IL-1β, IL-4, TNF-α, TGF-β and EGF at multiple time points after irradiation were similar in C57-WT and TGF-α(-/-) mice. TGF-α in lung tissue of C57-WT mice rose rapidly after irradiation and remained elevated through 20 weeks. TGF-α(-/-) mice had lower basal LOX expression than C57-WT mice. Both LOX expression and LOX activity were increased after irradiation in all mice but to a lesser degree in TGF-α(-/-) mice. Treatment of NIH-3T3 fibroblasts with TGF-α resulted in increases in proliferation, collagen production and LOX activity. These studies identify TGF-α as a critical mediator of radiation-induced lung injury and a novel therapeutic target in this setting. Further, these data implicate TGF-α as a mediator of collagen maturation through a TGF-β independent activation of lysyl oxidase.

Activated PAR-2 regulates pancreatic cancer progression through ILK/HIF-α-induced TGF-α expression and MEK/VEGF-A-mediated angiogenesis

Tissue factor initiates the process of thrombosis and activates cell signaling through protease-activated receptor-2 (PAR-2). The aim of this study was to investigate the pathological role of PAR-2 signaling in pancreatic cancer. We first demonstrated that activated PAR-2 up-regulated the protein expression of both hypoxia-inducible factor-1α (HIF-1α) and HIF-2α, resulting in enhanced transcription of transforming growth factor-α (TGF-α). Down-regulation of HIFs-α by siRNA or YC-1, an HIF inhibitor, resulted in depleted levels of TGF-α protein. Furthermore, PAR-2, through integrin-linked kinase (ILK) signaling, including the p-AKT, promoted HIF protein expression. Diminishing ILK by siRNA decreased the levels of PAR-2-induced p-AKT, HIFs-α, and TGF-α; our results suggest that ILK is involved in the PAR-2-mediated TGF-α via an HIF-α-dependent pathway. Furthermore, the culture medium from PAR-2-treated pancreatic cancer cells enhanced human umbilical vein endothelial cell proliferation and tube formation, which was blocked by the MEK inhibitor, PD98059. We also found that activated PAR-2 enhanced tumor angiogenesis through the release of vascular endothelial growth factor-A (VEGF-A) from cancer cells, independent of the ILK/HIFs-α pathways. Consistent with microarray analysis, activated PAR-2 induced TGF-A and VEGF-A gene expression. In conclusion, the activation of PAR-2 signaling induced human pancreatic cancer progression through the induction of TGF-α expression by ILK/HIFs-α, as well as through MEK/VEGF-A-mediated angiogenesis, and it plays a role in the interaction between cancer progression and cancer-related thrombosis.

EGF receptor is required for KRAS-induced pancreatic tumorigenesis

Initiation of pancreatic ductal adenocarcinoma (PDA) is definitively linked to activating mutations in the KRAS oncogene. However, PDA mouse models show that mutant Kras expression early in development gives rise to a normal pancreas, with tumors forming only after a long latency or pancreatitis induction. Here, we show that oncogenic KRAS upregulates endogenous EGFR expression and activation, the latter being dependent on the EGFR ligand sheddase, ADAM17. Genetic ablation or pharmacological inhibition of EGFR or ADAM17 effectively eliminates KRAS-driven tumorigenesis in vivo. Without EGFR activity, active RAS levels are not sufficient to induce robust MEK/ERK activity, a requirement for epithelial transformation.

The major vault protein mediates resistance to epidermal growth factor receptor inhibition in human hepatoma cells

To better understand the response of HCC to EGFR inhibition, we analyzed factors connected to the resistance of HCC cells against gefitinib. Sensitive HCC3 cells co-expressed EGFR and ErbB3 but lacked kinase-domain mutations in EGFR. Interestingly, expression of MVP was restricted to resistant cell lines, whereas ABCB1 and ABCC1 showed no association with gefitinib resistance. Moreover, ectopic MVP expression in HCC3 cells decreased gefitinib sensitivity, increased AKT phosphorylation and reduced the expression of inflammatory pathway-associated genes, whereas silencing of MVP in Hep3B and HepG2 cells increased sensitivity. These findings suggest MVP as a novel player in resistance against EGFR inhibition.

Inhibition of Rho-associated coiled-coil containing protein kinase enhances the activation of epidermal growth factor receptor in pancreatic cancer cells

BACKGROUND

Rho-associated coiled-coil containing protein kinase (Rho-kinase/ROCK) is involved in various cellular functions including cell proliferation, and is generally considered to be oncogenic, while some studies show that ROCK functions as a negative regulator of cancer progression. As a result, the precise role of ROCK remains controversial. We have previously reported that Rho-kinase/ROCK negatively regulates epidermal growth factor (EGF)-induced cell proliferation in SW480 colon cancer cells. In the present study, we investigated the role of ROCK in EGF receptor (EGFR) signaling in the pancreatic cancer cell lines, Panc1, KP3 and AsPc1.

RESULTS

In these cells, Y27632, a specific ROCK inhibitor, enhanced EGF-induced BrdU incorporation. The blockade of EGF stimulation utilizing anti-EGFR-neutralizing antibodies suppressed Panc1 cell proliferation. EGF induced RhoA activity, as well as the phosphorylation of cofilin and myosin light chain (MLC), both targets of ROCK signaling, and Y27632 suppressed both of these processes, indicating that the phosphorylation of cofilin and MLC by EGF occurs through ROCK in Panc1 cells. EGF-induced phosphorylation of EGFR at tyrosine residues was augmented when the cells were pretreated with Y27632 or were subjected to gene silencing using ROCK-siRNA. We also obtained similar results using transforming growth factor-α. In addition, EGF-induced phosphorylation of p44/p42 mitogen-activated protein kinase and Akt were also enhanced by Y27632 or ROCK-siRNA. Moreover, an immunofluorescence microscope study revealed that pretreatment with Y27632 delayed EGF-induced internalization of EGFR. Taken together, these data indicate that ROCK functions to switch off EGFR signaling by promoting the internalization of the EGFR.

CONCLUSIONS

While EGF first stimulates the activation of the EGFR and subsequently increases cancer cell proliferation, EGF concurrently induces the activation of ROCK, which then turns off the activated EGFR pathway via a negative feedback system.

Synergistic effect between erlotinib and MEK inhibitors in KRAS wild-type human pancreatic cancer cells

PURPOSE

The combination of erlotinib and gemcitabine has shown a small but statistically significant survival advantage when compared with gemcitabine alone in patients with advanced pancreatic cancer. However, the overall survival rate with the erlotinib and gemcitabine combination is still low. In this study, we sought to identify gene targets that, when inhibited, would enhance the activity of epidermal growth factor receptor (EGFR)-targeted therapies in pancreatic cancer cells.

EXPERIMENTAL DESIGN

A high-throughput RNA interference (RNAi) screen was carried out to identify candidate genes. Selected gene hits were further confirmed and mechanisms of action were further investigated using various assays.

RESULTS

Six gene hits from siRNA screening were confirmed to significantly sensitize BxPC-3 pancreatic cancer cells to erlotinib. One of the hits, mitogen-activated protein kinase (MAPK) 1, was selected for further mechanistic studies. Combination treatments of erlotinib and two MAP kinase kinase (MEK) inhibitors, RDEA119 and AZD6244, showed significant synergistic effect for both combinations (RDEA119-erlotinib and AZD6244-erlotinib) compared with the corresponding single drug treatments in pancreatic cancer cell lines with wild-type KRAS (BxPC-3 and Hs 700T) but not in cell lines with mutant KRAS (MIA PaCa-2 and PANC-1). The enhanced antitumor activity of the combination treatment was further verified in the BxPC-3 and MIA PaCa-2 mouse xenograft model. Examination of the MAPK signaling pathway by Western blotting indicated effective inhibition of the EGFR signaling by the drug combination in KRAS wild-type cells but not in KRAS mutant cells.

CONCLUSIONS

Overall, our results suggest that combination therapy of an EGFR and MEK inhibitors may have enhanced efficacy in patients with pancreatic cancer.

Enhanced pancreatic cancer gene therapy by combination of adenoviral vector expressing c-erb-B2 (Her-2/neu)-targeted immunotoxin with a replication-competent adenovirus or etoposide

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States, and even under optimal therapy these patients face a poor prognosis. Here we report a novel gene therapy-based strategy to battle this disease. We show that the majority of pancreatic tumors overexpress c-erb-B2, which therefore might serve as a target for novel therapies. On the basis of these findings, we developed an adenoviral vector [Ad-e23(scFv)-PE40] encoding a c-erb-B2 (Her-2/neu)-targeted immunotoxin. To improve viral gene delivery we coinfected the therapeutic adenovirus with a replication-competent adenovirus (RCAd) at low doses that enhanced the transduction efficiency of the former virus. In addition, we show that target gene expression can be enhanced by adding etoposide (VP16) at nontherapeutic doses. To investigate the therapeutic efficacy of our approach we established a mouse model for advanced pancreatic cancer disease by intraperitoneal injection of pancreatic cancer cell lines, resulting in multifocal peritoneal xenograft tumors. Administration of Ad-e23(scFv)-PE40 in combination with RCAd and VP16 significantly inhibited tumor growth in mice, with no apparent systemic toxicity. In this study we show that c-erb-B2 might be an effective molecular target in the treatment of pancreatic tumors and that coadministration of a therapeutic c-erb-B2-targeted, non-replication-competent adenovirus with an RCAd and VP16 could be a powerful approach to effectively deliver therapeutic genes to tumors. As demonstrated, this strategy can be employed to effectively treat pancreatic cancer in particular, but may be modified to treat other types of cancer as well.

Compounds in clinical Phase III and beyond

Targeted therapies against cancer have become more and more important. In particular, the inhibition of tumor angiogenesis and vascular targeting have been the focus of new treatment strategies. Numerous new substances were developed as angiogenesis inhibitors and evaluated in clinical trials for safety, tolerance, and efficacy. With positive study results, some of these molecules have already been approved for clinical use. For example, this is true for the vascular endothelial growth factor neutralizing antibody bevacizumab (BEV) in metastatic colorectal cancer, nonsmall cell lung cancer, renal cancer, and breast cancer. The tyrosine kinase (TK) inhibitors sorafenib and sunitinib have been approved for metastatic renal cancer as well as for hepatocellular carcinoma, and sunitinib has also been approved for gastrointestinal stroma tumors. In this chapter we try to give an overview of the substances currently investigated in Phase III studies and beyond with regard to antiangiogenesis in cancer therapy.

Advances in pancreatic cancer detection

Pancreatic cancer represents a major challenge for research studies and clinical management. No specific tumor marker for the diagnosis of pancreatic cancer exists. Therefore, extensive genomic, transcriptomic, and proteomic studies are being developed to identify candidate markers for use in high-throughput systems capable of large cohort screening. Understandably, the complex pathophysiology of pancreatic cancer requires sensitive and specific biomarkers that can improve both early diagnosis and therapeutic monitoring. The lack of a single diagnostic marker makes it likely that only a panel of biomarkers is capable of providing the appropriate combination of high sensitivity and specificity. Biomarker discovery using novel technology can improve prognostic upgrading and pinpoint new molecular targets for innovative therapy.

Epidermal growth factor receptor inhibitors in cancer treatment: advances, challenges and opportunities

Aberrant expression of the epidermal growth factor receptor (EGFR) system has been reported in a wide range of epithelial cancers. In some studies, this has also been associated with a poor prognosis and resistance to the conventional forms of therapies. These discoveries have led to the strategic development of several kinds of EGFR inhibitors, five of which have gained US Food and Drug Administration approval for the treatment of patients with non-small-cell lung cancer (gefitinib and erlotinib), metastatic colorectal cancer (cetuximab and panitumumab), head and neck (cetuximab), pancreatic cancer (erlotinib) and breast (lapatinib) cancer. Despite these advances and recent studies on the predictive value of activating EGFR mutation and KRAS mutations with response in non-small-cell lung cancer and colon cancer patients, there is currently no reliable predictive marker for response to therapy with the anti-EGFR monoclonal antibodies cetuximab and panitumumab or the small molecule EGFR tyrosine kinase inhibitors gefitinib and erlotinib. In particular, there has been no clear association between the expression of EGFR, determined by the US Food and Drug Administration-approved EGFR PharmDX kit, and response to the EGFR inhibitors. Here, we discuss some of the controversial data and explanatory factors as well as future studies for the establishment of more reliable markers for response to therapy with EGFR inhibitors. Such investigations should lead to the selection of a more specific subpopulation of cancer patients who benefit from therapy with EGFR inhibitors, but equally to spare those who will receive no benefit or a detrimental effect from such biological agents.

Results of a phase I trial of 12 patients with locally advanced pancreatic carcinoma combining gefitinib, paclitaxel, and 3-dimensional conformal radiation: report of toxicity and evaluation of circulating K-ras as a potential biomarker of response to therapy

OBJECTIVE

To evaluate the toxicity of daily gefitinib, an epidermal growth factor receptor-tyrosine kinase inhibitor, with concurrent chemoradiation (CRT) in patients with locally advanced pancreatic adenocarcinoma and prospectively evaluate plasma k-ras as a potential marker of response to gefitinib and CRT.

METHODS

Eleven of 12 eligible patients enrolled received a 7-day induction of gefitinib (250 mg PO) followed by daily gefitinib with concurrent CRT. Patients received 50.4 Gy/28 fractions of external beam radiation with weekly paclitaxel (40 mg/m IV) followed by maintenance on gefitinib. Plasma k-ras codon 12 mutations were detected using a two-stage restriction fragment length polymorphism-polymerase chain reaction assay on patients' plasma both before and after therapy. Mutations were confirmed by direct sequencing.

RESULTS

Common adverse events included grade 1 skin rash (63%), grade 1 to 2 gastrointestinal symptoms including anorexia, nausea, vomiting, and diarrhea occurred in 63% of patients, grade 3 nausea occurred in 45% of patients. Three patients did not complete therapy, only one was possibly associated with study drug. K-ras mutations were detected in the pre-gefitinib plasma of 5/11 patients and in the matched tumor tissue of 3/4 patients. In patients where k-ras mutations were undetectable post-treatment, survival times were favorable.

CONCLUSIONS

Combination of daily gefitinib with concurrent CRT in this locally advanced pancreatic cancer population was reasonably tolerated. Rapid changes in serum k-ras may provide critical information as to the efficacy of a novel agent and assist in tailoring treatment for cancers of the pancreas.

Preclinical activity of gefitinib in non-keratinizing nasopharyngeal carcinoma cell lines and biomarkers of response

This study evaluated the preclinical activity and molecular predictors of response to gefitinib (Iressa®, Astra Zeneca Inc, UK) in nasopharyngeal carcinoma (NPC). The activity of gefitinib was evaluated in four human NPC cell lines—HK1, HONE-1, CNE2, C666-1. A representative gefitinib-sensitive (HK1, IC₅₀ = 250 nM) and gefitinib-resistant cell line (HONE-1, IC₅₀ > 15 μM) were selected and compared for expression of epidermal growth factor receptor (EGFR) and related ligands, and activation of downstream proteins. Gefitinib induced G1 cycle arrest, apoptosis and inhibited cell invasion more significantly in HK1 than HONE-1 cells. HK1 expressed higher levels of p-EGFR, lower p-AKT and phospho-signal transducer and activator of transcription 3 (p-STAT3) than other cell lines. EGFR gene was found to be amplified in HK1. Gefitinib at IC₅₀ concentrations significantly suppressed EGF-induced activation of p-EGFR, phospho-mitogen-activated protein kinase (p-MAPK) and p-STAT3, but p-AKT showed persistent activation in HK1 and HONE-1 cells. There was no difference in EGFR-ligand expression between the 4 NPC cell lines. In NPC samples derived from non-responders to gefitinib, 50% and 60% showed cytoplasmic and nuclear pi-EGFR expression, respectively, and 33% showed p-AKT expression. EGFR or KRAS mutations were not detected. This study suggests that most NPC cell lines are intrinsically resistant to gefitinib (except HK1 cells), and further studies are needed to confirm whether EGFR gene amplification and persistent AKT activation may influence response to gefitinib in NPC.

MEK, p38, and PI-3K mediate cross talk between EGFR and TNFR in enhancing hepatocyte growth factor production from human mesenchymal stem cells

Human bone marrow mesenchymal stem cells (MSCs) are a potent source of growth factors, which are partly responsible for their beneficial paracrine effects. We reported previously that transforming growth factor-alpha (TGF-alpha), a putative mediator of wound healing and the injury response, increases the release of vascular endothelial growth factor (VEGF), augments tumor necrosis factor-alpha (TNF-alpha)-stimulated VEGF production, and activates mitogen-activated protein kinases and phosphatidylinositol 3-kinase (PI-3K) pathway in human MSCs. The experiments described in this report indicate that TGF-alpha increases MSC-derived hepatocyte growth factor (HGF) production. TGF-alpha-stimulated HGF production was abolished by inhibition of MEK, p38, PI-3K, or by small interfering RNA (siRNA) targeting TNF receptor 2 (TNFR2), but was not attenuated by siRNA targeting TNF receptor 1 (TNFR1). Ablation of TNFR1 significantly increased basal and stimulated HGF. A potent synergy between TGF-alpha and TNF-alpha was noted in MSC HGF production. This synergistic effect was abolished by MEK, P38, PI-3K inhibition, or by ablation of both TNF receptors using siRNA. We conclude that 1) novel cross talk occurs between tumor necrosis factor receptor and TGF-alpha/epidermal growth factor receptor in stimulating MSC HGF production; 2) this cross talk is mediated, at least partially, via activation of MEK, p38, and PI-3K; 3) TGF-alpha stimulates MSCs to produce HGF by MEK, p38, PI-3K, and TNFR2-dependent mechanisms; and 4) TNFR1 acts to decrease basal TGF-alpha and TNF-alpha-stimulated HGF.

Delta-crystallin enhancer binding factor 1 controls the epithelial to mesenchymal transition phenotype and resistance to the epidermal growth factor receptor inhibitor erlotinib in human head and neck squamous cell carcinoma lines

PURPOSE

Although the epidermal growth factor receptor (EGFR) is overexpressed in a majority of head and neck squamous cell carcinomas (HNSCC), only a minority of patients derive substantial clinical benefit from EGFR inhibitors. We initiated the present study to identify the mechanisms underlying erlotinib resistance in a panel of HNSCC cell lines.

METHODS

We used [(3)H]thymidine incorporation to characterize the heterogeneity of responsiveness to erlotinib-mediated growth inhibition in a panel of 27 human HNSCC cells. We characterized the molecular mechanisms involved in resistance using a representative subset of six erlotinib-sensitive and erlotinib-resistant HNSCC lines.

RESULTS

Erlotinib had heterogeneous effects on DNA synthesis in HNSCC cells that correlated closely with molecular markers of epithelial to mesenchymal transition (EMT). Specifically, the drug-sensitive lines expressed high levels of E-cadherin and showed limited invasion and migration capabilities. In contrast, the erlotinib-resistant HNSCC lines expressed high levels of the E-cadherin repressor delta-crystallin enhancer binding factor 1 (deltaEF1; Zeb-1) and other mesenchymal markers and low levels of E-cadherin, and they were highly invasive and migratory. Small interfering RNA-mediated knockdown of deltaEF1 in the erlotinib-resistant cell lines (1386LN and UMSCC1) resulted in up-regulation of E-cadherin and increased sensitivity to erlotinib in an E-cadherin-dependent manner.

CONCLUSIONS

DeltaEF1 controls the mesenchymal phenotype and drives erlotinib resistance in HNSCC cells. E-cadherin and deltaEF1 may prove to be useful markers in predicting EGFR inhibitor responsiveness.

Role of ErbB family receptor tyrosine kinases in intrahepatic cholangiocarcinoma

Aberrant expression and signaling of epidermal growth factor receptor (ErbB) family receptor tyrosine kinases, most notably that of ErbB2 and ErbB1, have been implicated in the molecular pathogenesis of intrahepatic cholangiocarcinoma. Constitutive overexpression of ErbB2 and/or ErbB1 in malignant cholangiocytes has raised interest in the possibility that agents which selectively target these receptors could potentially be effective in cholangiocarcinoma therapy. However, current experience with such ErbB-directed therapies have at best produced only modest responses in patients with biliary tract cancers. This review provides a comprehensive and critical analysis of both preclinical and clinical studies aimed at assessing the role of altered ErbB2 and/or ErbB1 expression, genetic modifications, and dysregulated signaling on cholangiocarcinoma development and progression. Specific limitations in experimental approaches that have been used to assess human cholangiocarcinoma specimens for ErbB2 and/or ErbB1 overexpression and gene amplification are discussed. In addition, current rodent models of intrahepatic cholangiocarcinogenesis associated with constitutive ErbB2 overexpression are reviewed. Select interactive relationships between ErbB2 or ErbB1 with other relevant molecular signaling pathways associated with intrahepatic cholangiocarcinoma development and progression are also detailed, including those linking ErbB receptors to bile acid, cyclooxygenase-2, interleukin-6/gp130, transmembrane mucins, hepatocyte growth factor/Met, and vascular endothelial growth factor signaling. Lastly, various factors that can limit therapeutic efficacy of ErbB-targeted agents against cholangiocarcinoma are considered.

Markers involved in resistance to cytotoxics and targeted therapeutics in pancreatic cancer

Pancreatic cancer retains a poor prognosis among the gastrointestinal cancers and remains a challenge in oncology. In 1997, gemcitabine became the standard of care in metastatic setting. In the last decades, despite a number of clinical trials assessing novel cytotoxic agents and cell signaling inhibitors, overall survival has reached a plateau that remains difficult to improve. Development of mechanisms implicated in intrinsic and acquired resistance to chemotherapy are considered to play a key role that could explain the limited benefit of most treatment in pancreatic cancers. Key molecular factors implicated in this process include: deficiencies in drugs uptake, activations of DNA repair pathways, resistance to apoptosis, and tumor microenvironment. Moreover, for cell signaling inhibitors, mutations in kinase domains, activation of alternative pathways, mutations of genes downstream of the target, activation of autocrine/paracrine pathways and/or feed-back amplification of the target represent the most important mechanisms achieving resistance of pancreatic cancer cells.

Molecular biology of pancreatic cancer

Pancreatic cancer is a leading cause of cancer death. This devastating disease has the horrible honour of close to equal incidence and mortality rates. Late diagnosis and a constitutive resistance to every chemotherapy approach are responsible for this scenario. However, molecular biology tools in cooperation with translational efforts have dissected several secrets that underlie pancreatic cancer. Progressive acquisition of malignant, invasive phenotypes from pre-malignant lesions, recent revelations on core signalling pathways and new targeted designed trials offer a better future for pancreatic cancer patients. This review will summarise recent advances in the molecular biology of pancreatic cancer.

Nestin expression correlates with nerve and retroperitoneal tissue invasion in pancreatic cancer

Nestin was first described as an intermediate filament protein expressed in neuroepithelial stem cells. Nestin expression has also been reported in brain tumors, schwannomas, gastrointestinal stromal tumors, and melanomas. In the pancreas, Nestin expression has been detected in exocrine and mesenchymal cells, including stellate cells, pericytes, and endothelial cells. In the present study, we examined Nestin expression in human pancreatic ductal adenocarcinoma and sought to determine its role in this malignancy. Reverse transcription-polymerase chain reaction analysis demonstrated the presence of Nestin mRNA in all 10 tested pancreatic cancer cell lines, and quantitative reverse transcription-polymerase chain reaction revealed that Nestin mRNA levels were highest in PANC-1 cells and lowest in PK-8 cells. Immunofluorescent analysis revealed that Nestin localized in the outer cytoplasm of PANC-1 cells. Nestin immunoreactivity was present in the cancer cells in 20 (33.3%) of 60 cancer cases, and its expression was confirmed by in situ hybridization. Nestin expression was also increased in peripheral nerve fibers adjacent to cancer cells and in peripheral nerve fibers invaded by cancer cells. Clinicopathologically, there was a statistically significant association between Nestin expression in pancreatic cancer cells and nerve invasion (P = .010) and the presence of cancer cells in the tumor resection margins (P = .003). Nestin-positive cases exhibited similar survival after resection by comparison with Nestin-negative cases, irrespective of whether they were given adjuvant therapy. These findings indicate that Nestin expression in pancreatic cancer cells may contribute to nerve and stromal invasion in this malignancy.

Molecular targeted therapies for pancreatic cancer

BACKGROUND

Pancreatic cancer cells express different mutations that increase the aggressiveness and confer resistance to conventional chemotherapy and radiotherapy. Molecules that selectively bind and inhibit these mutations are effective in other solid tumors and are now emerging as a complementary therapy in pancreatic cancer. The objective of this review is to describe the effect of drugs that inhibit specific mutations present in pancreatic cancer with special emphasis on clinical trials.

DATA SOURCES

We reviewed the English-language literature (MedLine) addressing the role of drugs that target mutations present in pancreatic cancer. Both preclinical and clinical studies were included.

CONCLUSIONS

Preclinical evidence supports the combination of conventional approved therapies plus drugs that block epidermal growth factor receptor and vascular growth endothelial factor or induce apoptosis. However, most of the current clinical evidence is limited to small phase I trials evaluating the toxicity and safety of these regimens. The results of additional randomized trials that are still undergoing will clarify the role of these drugs in pancreatic cancer.

Human Mena+11a isoform serves as a marker of epithelial phenotype and sensitivity to epidermal growth factor receptor inhibition in human pancreatic cancer cell lines

PURPOSE

hMena, member of the enabled/vasodilator-stimulated phosphoprotein family, is a cytoskeletal protein that is involved in the regulation of cell motility and adhesion. The aim of this study was to determine whether or not the expression of hMena isoforms correlated with sensitivity to EGFR tyrosine kinase inhibitors and could serve as markers with potential clinical use.

EXPERIMENTAL DESIGN

Human pancreatic ductal adenocarcinoma cell lines were characterized for in vitro sensitivity to erlotinib, expression of HER family receptors, markers of epithelial to mesenchymal transition, and expression of hMena and its isoform hMena(+11a). The effects of epidermal growth factor (EGF) and erlotinib on hMena expression as well as the effect of hMena knockdown on cell proliferation were also evaluated.

RESULTS

hMena was detected in all of the pancreatic tumor cell lines tested as well as in the majority of the human tumor samples [primary (92%) and metastatic (86%)]. Intriguingly, in vitro hMena(+11a) isoform was specifically associated with an epithelial phenotype, EGFR dependency, and sensitivity to erlotinib. In epithelial BxPC3 cells, epidermal growth factor up-regulated hMena/hMena(+11a) and erlotinib down-regulated expression. hMena knockdown reduced cell proliferation and mitogen-activated protein kinase and AKT activation in BxPC3 cells, and promoted the growth inhibitory effects of erlotinib.

CONCLUSIONS

Collectively, our data indicate that the hMena(+11a) isoform is associated with an epithelial phenotype and identifies EGFR-dependent cell lines that are sensitive to the EGFR inhibitor erlotinib. The availability of anti-hMena(+11a)-specific probes may offer a new tool in pancreatic cancer management if these results can be verified prospectively in cancer patients.

Biological approaches to therapy of pancreatic cancer

Pancreatic cancer is a lethal disease and notoriously difficult to treat. Only a small proportion is curative by surgical resection, whilst standard chemotherapy for patients with advanced disease has only modest effect with substantial toxicity. Clearly there is a need for the continual development of novel therapeutic agents to improve the current situation. Improvement of our understanding of the disease has generated a large number of studies on biological approaches targeting the molecular abnormalities of pancreatic cancer, including gene therapy and signal transduction inhibition, antiangiogenic and matrix metalloproteinase inhibition, oncolytic viral therapy and immunotherapy. This article provides a review of these approaches, both investigated in the laboratories and in subsequent clinical trials.

TGF-alpha increases human mesenchymal stem cell-secreted VEGF by MEK- and PI3-K- but not JNK- or ERK-dependent mechanisms

Transforming growth factor-alpha (TGF-alpha) may be an important mediator of wound healing and the injury response. Human bone marrow mesenchymal stem cells (MSCs) release VEGF as a potentially beneficial paracrine response; however, it remains unknown whether TGF-alpha stimulates the production of VEGF from MSCs and, if so, by which mechanisms. We hypothesized that TGF-alpha would increase human MSC VEGF production by MAP kinase kinase (MAPKK/MEK), phosphatidylinositol 3-kinase (PI3-K)-, ERK, and JNK-dependent mechanisms. To study this, MSCs were cultured and divided into the following groups: 1) with vehicle; 2) with various stimulants alone: TGF-alpha, TNF-alpha, or TGF-alpha+TNF-alpha; 3) with individual kinase inhibitors alone (two different inhibitors for each of the following kinases: MEK, PI3-K, ERK, or JNK); and 4) with the above stimulants and each of the eight inhibitors. After 24-h incubation, a TGF-alpha dose-response curve demonstrated that low-dose TGF-alpha (500 pg/ml) suppressed MSC production of VEGF compared with vehicle (502 +/- 16 pg/10(5) cells/ml to 332 +/- 9 pg/10(5) cells/ml), while high-dose TGF-alpha (250 ng/ml) significantly increased MSC VEGF production (603 +/- 24 pg/10(5) cells/ml). High-dose TGF-alpha also increased TNF-alpha-stimulated release of VEGF from MSCs. MSCs exposed to TGF-alpha and/or TNF-alpha also demonstrated increased activation of PI3-K, JNK, and ERK. The TGF-alpha-stimulated production of VEGF by MSCs and the additive effect of TNF-alpha and TGF-alpha on VEGF production were abolished by MEK and PI3-K inhibition, but not ERK or JNK inhibition. Our data suggest that TGF-alpha increases VEGF production in MSCs via MEK- and PI3-K- but not ERK- or JNK-dependent mechanisms.

Synergic antiproliferative and antiangiogenic effects of EGFR and mTor inhibitors on pancreatic cancer cells

The in vitro efficacy of both EGFR inhibitor gefitinib and mTor inhibitor rapamycin, either administrated alone or in different combination schedules, was analysed in four pancreas cancer cell lines. Both drugs were found to induce cell growth inhibition, apoptosis as well as a slight but stable accumulation of cells in the G0/G1 phase. In all cell lines, neither gefitinib nor rapamycin affected EGFR and the expression of its downstream effectors. By contrast, gefitinib inhibited in a fast and completely way p-EGFR and partially p-Akt while a 3 days-rapamycin exposure resulted in the inhibition of the expression of both mTor and p70S6K. Moreover, after early stimulation, the mTor inhibitor produced a progressive, and almost complete inhibition of p-Akt. The analysis of combined gefitinib and rapamycin administration showed a clear schedule-dependent activity which turned out to be synergic only when gefitinib was given before rapamycin. This synergism seemed to depend on increase of both p-Akt and p70S6K inhibition, the greater the induction of apoptosis, the higher the decrease in cell cycle rate. Moreover, the antiangiogenic activity of the two drugs given in combination was demonstrated by a strong reduction of VEGF release which turned out to be more pronounced in the synergic schedule, and HIF-1alpha inhibition-independent. Our results suggest that the schedule of gefitinib followed by rapamycin, acting at different levels of the EGFR cellular pathway, could induce antitumor and antiangiogenic effects of clinical interest in the pancreas cancer model.

Expression of epidermal growth factor (EGF)/transforming growth factor-alpha by human lung cancer cells determines their response to EGF receptor tyrosine kinase inhibition in the lungs of mice

Epidermal growth factor receptor (EGFR) has been extensively targeted in the treatment of non-small cell lung cancer, producing responses in a small number of patients. To study the role of ligand expression in mediating response to EGFR antagonism, we injected NCI-H441 [EGFR and EGF/transforming growth factor-alpha (TGF-alpha) positive] or PC14-PE6 (EGFR positive and EGF/TGF-alpha negative) human lung adenocarcinoma cells into the lungs of nude mice. We randomized the mice to receive treatment with the EGFR tyrosine kinase inhibitors gefitinib or AEE788 or vehicle. Treatment of mice bearing NCI-H441 but not PC14-PE6 lung tumors resulted in a significant reduction in primary tumor growth, pleural effusion, and lymph node metastasis. Immunohistochemical analyses revealed that NCI-H441 and PC14-PE6 cells expressed EGFR but that the expression of EGF/TGF-alpha was high in NCI-H441 cells and very low in PC14-PE6 cells. Consequently, EGFR was activated in both tumor and tumor-associated endothelial cells in the NCI-H441 tumors but not in the PC14-PE6 tumors. Antagonism of EGFR signaling by treatment of mice with AEE788 decreased proliferation and increased apoptosis of both tumor cells and tumor-associated endothelial cells in NCI-H441 tumors but not in PC14-PE6 tumors. However, after transfection of PC14-PE6 cells with TGF-alpha, lung tumors derived from the transfected cells expressed and activated EGFR in both tumor and tumor-associated endothelial cells and tumors responded to treatment with AEE788. Collectively, these results strongly suggest that the response of human lung cancers growing orthotopically in mice to the inhibition of EGFR signaling is determined by ligand (EGF/TGF-alpha) expression by tumor cells. Our findings provide an additional explanation for the susceptibility of lung cancers to treatment with EGFR tyrosine kinase inhibitors.

Targeting signal transduction in pancreatic cancer treatment

Pancreatic cancer is a lethal disease with a 5-year survival rate of 4%. The only opportunity for improved survival continues to be complete surgical resection for those with localized disease. Although chemotherapeutic options are limited for the few patients with resectable disease, this problem is even more magnified in the majority (85%) of patients with unresectable or metastastic disease. Therefore, there is an urgent need for improved therapeutic options. The recent success of inhibitors of signal transduction for the treatment of other cancers supports the need to identify and validate aberrant signaling pathways important for pancreatic tumor growth. This review focuses on the validation of specific signaling networks and the present status of inhibitors of these pathways as therapeutic approaches for pancreatic cancer treatment.

Molecular correlates of gefitinib responsiveness in human bladder cancer cells

We characterized the effects of the small molecule epidermal growth factor receptor (EGFR) inhibitor gefitinib (ZD1839, Iressa) on cell proliferation in a panel of 17 human bladder cancer cell lines. Gefitinib inhibited DNA synthesis in a concentration-dependent fashion in 6 of 17 lines. Growth inhibition was associated with p27(Kip1) accumulation and decreased cyclin-dependent kinase 2 activity. Gefitinib also inhibited baseline EGFR, AKT, and extracellular signal-regulated kinase (ERK) phosphorylation in the EGFR-dependent cells maintained in serum-free medium, whereas it had no effect on baseline EGFR or ERK phosphorylation in the EGFR-independent cells. Analyses of candidate markers of EGFR dependency revealed that the gefitinib-sensitive cells expressed higher surface EGFR levels than the gefitinib-resistant lines. Gefitinib-sensitive cells generally expressed higher levels of E-cadherin and lower levels of vimentin than the gefitinib-resistant cells, but these correlations were not perfect, suggesting that these markers of epithelial-mesenchymal transition cannot be used by themselves to prospectively predict EGFR-dependent growth. Together, our results show that bladder cancer cells are markedly heterogeneous with respect to their sensitivity to EGFR antagonists. Although surface EGFR levels and epithelial-mesenchymal transition status seem to roughly correlate with responsiveness, they cannot be used by themselves to identify bladder tumors that will be sensitive to EGFR-directed therapy. However, comparing levels of p27(Kip1) or DNA synthesis before and after gefitinib exposure does identify the drug-sensitive cells.

Gefitinib reverses TRAIL resistance in human bladder cancer cell lines via inhibition of AKT-mediated X-linked inhibitor of apoptosis protein expression

In a previous study, we found that the small-molecule epidermal growth factor receptor (EGFR) inhibitor gefitinib (ZD1839, Iressa) blocked cell proliferation at biologically relevant concentrations in approximately one third (6 of 17) of human bladder cancer cell lines examined. Here, we studied the effects of gefitinib on apoptosis in a representative subset of the same panel of cells. The drug had modest effects on DNA fragmentation as a single agent at concentrations that produced strong growth inhibition (< or =1 micromol/L) and also failed to promote apoptosis induced by conventional chemotherapeutic agents (gemcitabine and paclitaxel). However, gefitinib did interact with recombinant human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to induce high levels of apoptosis in gefitinib-responsive but not gefitinib-unresponsive lines. The molecular mechanisms involved down-regulation of active AKT and X-linked inhibitor of apoptosis protein (XIAP) expression and were mimicked by chemical inhibitors of the phosphatidylinositol 3-kinase/AKT pathway but not of the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase/ERK pathway. Furthermore, direct small interfering RNA-mediated knockdown of AKT resulted in down-regulation of XIAP and TRAIL sensitization, and knockdown of XIAP itself was sufficient to reverse TRAIL resistance. Together, our results show that EGFR pathway activation limits TRAIL-induced apoptosis via an AKT- and XIAP-dependent mechanism in EGFR-dependent human bladder cancer cells, providing the conceptual framework for a further evaluation of the combination in relevant preclinical in vivo models.

Radiation-induced cell signaling: inside-out and outside-in

Exposure of tumor cells to clinically relevant doses of ionizing radiation causes DNA damage as well as mitochondria-dependent generation of reactive oxygen species. DNA damage causes activation of ataxia telangiectasia mutated and ataxia telangiectasia mutated and Rad3-related protein, which induce cell cycle checkpoints and also modulate the activation of prosurvival and proapoptotic signaling pathways, such as extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun NH(2)-terminal kinase 1/2, respectively. Radiation causes a rapid reactive oxygen species-dependent activation of ERBB family and other tyrosine kinases, leading to activation of RAS proteins and multiple protective downstream signaling pathways (e.g., AKT and ERK1/2), which alter transcription factor function and the apoptotic threshold of cells. The initial radiation-induced activation of ERK1/2 can promote the cleavage and release of paracrine ligands, which cause a temporally delayed reactivation of receptors and intracellular signaling pathways in irradiated and unirradiated bystander cells. Hence, signals from within the cell can promote activation of membrane-associated receptors, which signal back into the cytosol: signaling from inside the cell outward to receptors and then inward again via kinase pathways. However, cytosolic signaling can also cause release of membrane-associated paracrine factors, and thus, paracrine signals from outside of the cell can promote activation of growth factor receptors: signaling from the outside inward. The ultimate consequence of these signaling events after multiple exposures may be to reprogram the irradiated and affected bystander cells in terms of their expression levels of growth-regulatory and cell survival proteins, resulting in altered mitogenic rates and thresholds at which genotoxic stresses cause cell death. Inhibition of signaling in one and/or multiple survival pathways enhances radiosensitivity. Prolonged inhibition of any one of these pathways, however, gives rise to lineages of cells, which have become resistant to the inhibitor drug, by evolutionary selection for the clonal outgrowth of cells with point mutations in the specific targeted protein that make the target protein drug resistant or by the reprogramming of multiple signaling processes within all cells, to maintain viability. Thus, tumor cells are dynamic with respect to their reliance on specific cell signaling pathways to exist and rapidly adapt to repeated toxic challenges in an attempt to maintain tumor cell survival.

Activation of downstream epidermal growth factor receptor (EGFR) signaling provides gefitinib-resistance in cells carrying EGFR mutation

Patients with pulmonary adenocarcinoma carrying the epidermal growth factor receptor (EGFR) mutation tend to display dramatic clinical response to treatment with the EGFR tyrosine kinase inhibitor gefitinib. Unfortunately, in many cases the cancer cells eventually acquire resistance, and this limits the duration of efficacy. To gain insight into these acquired resistance mechanisms, we first prepared HEK293T cell line stably transfected with either wild-type (WT) or mutant (L858R) EGFR, and then expressed oncogenic K-Ras12V mutant in the latter transfectant. Although 293T cells expressing wild-type EGFR did not show any growth inhibition by gefitinib treatment similarly to the non-transfected cells, the cells expressing the EGFR-L858R were exquisitely sensitive. Consistently, phospho-Akt levels were decreased in response to gefitinib in cells expressing EGFR-L858R but not in cells with EGFR-WT. In contrast, 293T cells expressing both EGFR-L858R and oncogenic K-Ras were able to proliferate even in the presence of high concentration of gefitinib probably by inducing Erk1/2 activation. We also expressed K-Ras12V in the gefitinib-sensitive pulmonary adenocarcinoma cell line PC-9, which harbors an in-frame deletion in the EGFR gene. The activated K-Ras inhibited the effects of gefitinib treatment on cell growth, cell death induction and levels of phospho-Akt, as well as phospho-Erk. These data indicate that activated Ras could substitute most of the upstream EGFR signal, and are consistent with the hypothesis that mutational activation of targets immediately downstream from the EGFR could induce the secondary resistance to gefitinib in patients with lung cancer carrying EGFR mutation.

Erlotinib plus gemcitabine in patients with unresectable pancreatic cancer and other solid tumors: phase IB trial

PURPOSE

The purpose of this phase IB trial was to evaluate the tolerability, pharmacokinetics and preliminary evidence of antitumor activity of erlotinib plus gemcitabine in patients with pancreatic cancer and other solid tumors.

PATIENTS AND METHODS

Patients included those with advanced pancreatic adenocarcinoma or other malignancies potentially responsive to gemcitabine. In the escalating phase of the trial, patients were enrolled in sequential cohorts using 100 or 150 mg oral daily dosing of erlotinib. Gemcitabine dose was 1,000 mg/m(2) weekly x 7 (first cycle), then weekly x 3, every 4 weeks.

RESULTS

Twenty-six patients completed at least one course on study. In Cohort IA, at the 100 mg/day dose of erlotinib, three patients have developed grade 3 transaminase elevations. After stricter inclusion criteria were adopted (Cohort IB), no additional events of grade 3 transaminase elevations were observed and the dose of erlotinib was escalated to 150 mg/day (Cohorts IB and IIB) without reaching dose-limiting toxicities. The most common toxicities included diarrhea, skin rash, fatigue and neutropenia. The pharmacokinetic analyses did not reveal any significant interactions between erlotinib and gemcitabine. Objective responses were seen in two patients: cholangiocarcinoma and pancreatic cancer. Patients with unresectable or metastatic pancreatic cancer (n = 15) had a median progression-free survival of 289 days, the estimated overall survival of 389 days (12.5 months), and a 1-year survival rate of 51%.

CONCLUSION

The 150 mg/day dose of erlotinib can be safely administered in combination with standard dose gemcitabine in selected patients with pancreatic cancer and other advanced solid tumors. Promising antitumor activity has been observed in patients with pancreatic cancer.