Blockade Of EGFR Research Articles

134P PROGNOSTIC FACTORS FOR SURVIVAL IN ADULT PATIENTS (PTS) WITH METASTATIC NON-SMALL CELL LUNG CANCER AFTER THE FIRST-LINE CHEMOTHERAPY

responses, progression free survival, adverse events and quality of life functions. Results: Out of the 27 patients 13 were males and 14 females. Both arms were well matched for disease stage, performance status and age. In the Lapatinib arm, 8/13 patients (61.5%) had partial response and 2/13 patients (15.3%) had stable disease. 3/13 patients (23%) had progressive disease. In chemotherapy-only arm 5/14 patients had partial response (36%) while 3/14 patients (21%) had stable disease. 6/14 patients (43%) had progressive disease. The partial response rates were significantly more in Lapatinib arm (p = 0.03) while partial response plus stable disease were not significantly different between two arms (p = 0.3). The median disease free survival was significantly more in Lapatinib arm than the chemotherapy-only arm (7.8 months vs 5.5 months) (p = 0.02). Median overall survival was not reached in either arm. The treatment was well tolerated in both the arms with no major skin rash and cardiotoxicity seen with Lapatinib Conclusions: There is a good rationale to use dual blockade of Her2 and EGFR along with chemotherapy in NSCLC. As found in this study, it may translate into better tumor responses and even better survival especially in never or seldom smokers. This hypothesis needs to be tested in large multicenter trials.

Effects of the combined blockade of EGFR and ErbB-2 on signal transduction and regulation of cell cycle regulatory proteins in breast cancer cells.

Abstract Abstract #2130 Co-expression of EGFR and ErbB-2 occurs in a subset of primary breast carcinoma, and it is associated with worse prognosis. We previously demonstrated that treatment of breast cancer cells that express both receptors with a combination of the EGFR tyrosine kinase inhibitor gefitinib (G) and the anti-ErbB-2 monoclonal antibody herceptin (H) results in a synergistic anti-tumor effect. Such combination failed to show significant activity in a phase I/II clinical trial. However, patients enrolled in this trial were not selected for expression of EGFR. We explored the molecular mechanisms involved in the synergism of G and H in breast cancer cells. Treatment of both SK-BR-3 and BT-474 cells with a combination of G+H produced a more significant reduction of AKT and p42/p44-MAPK (MAPK) activation as compared with treatment with a single agent. The combination also produced a more prolonged blockade of both signalling pathways. In agreement with these findings, treatment with G+H induced a more pronounced accumulation of cells in the G0/G1 phase of the cell cycle as compared with treatment with a single drug. A sub-G0/G1 peak, suggestive of apoptosis, was evident in cells treated with the combination but not with G or H. The combination of G+H produced a more significant increase in the levels of p27kip1 and of hypophosphorylated forms of pRb2, and a more significant decrease in the levels of Cyclin D1 and survivin as compared with a single agent. Analysis of p27kip1 protein stability, in presence of the protein synthesis inhibitor cycloheximide, revealed that both G and the combination of G+H significantly increased the stability of p27kip1, with the combination showing higher effects. Furthermore, breast cancer cells treated with the combination expressed higher levels of p27kip1 mRNA as compared with cells treated with a single drug. The combination also induced a significant increase in the nuclear levels of the FKHRL-1 transcription factor that was not observed in cells treated with G or H alone. Treatment of breast cancer cells with the dual EGFR/ErbB-2 inhibitor lapatinib produced an increase in the levels of p27kip1 and of hypophosphorylated pRb2, and a decrease in the levels of Cyclin D1 and survivin comparable to that observed following treatment with the combination of G+H. In addition, an increase in p27kip1 mRNA and in the nuclear levels of FKHRL-1 was induced in breast cancer cells by treatment with lapatinib. These findings suggest that the synergistic anti-tumor effects deriving from EGFR and ErbB-2 blockade are mediated by significant alterations in the expression of cell cycle regulatory proteins, including transcriptional and post-transcriptional regulation of p27kip1 expression. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2130.

Feedback Mechanisms Promote Cooperativity for Small Molecule Inhibitors of Epidermal and Insulin-Like Growth Factor Receptors

Epidermal growth factor receptor (EGFR) and insulin-like growth factor-I receptor (IGF-IR) can cooperate to regulate tumor growth and survival, and synergistic growth inhibition has been reported for combined blockade of EGFR and IGF-IR. However, in preclinical models, only a subset of tumors exhibit high sensitivity to this combination, highlighting the potential need for patient selection to optimize clinical efficacy. Herein, we have characterized the molecular basis for cooperative growth inhibition upon dual EGFR and IGF-IR blockade and provide biomarkers that seem to differentiate response. We find for epithelial, but not for mesenchymal-like, tumor cells that Akt is controlled cooperatively by EGFR and IGF-IR. This correlates with synergistic apoptosis and growth inhibition in vitro and growth regression in vivo upon combined blockade of both receptors. We identified two molecular aspects contributing to synergy: (a) inhibition of EGFR or IGF-IR individually promotes activation of the reciprocal receptor; (b) inhibition of EGFR-directed mitogen-activated protein kinase (MAPK) shifts regulation of Akt from EGFR toward IGF-IR. Targeting the MAPK pathway through downstream MAPK/extracellular signal-regulated kinase kinase (MEK) antagonism similarly promoted IGF-driven pAkt and synergism with IGF-IR inhibition. Mechanistically, we find that inhibition of the MAPK pathway circumvents a negative feedback loop imposed on the IGF-IR- insulin receptor substrate 1 (IRS-1) signaling complex, a molecular scenario that parallels the negative feedback loop between mTOR-p70S6K and IRS-1 that mediates rapamycin-directed IGF-IR signaling. Collectively, these data show that resistance to inhibition of MEK, mTOR, and EGFR is associated with enhanced IGF-IR-directed Akt signaling, where all affect feedback loops converging at the level of IRS-1.

Versican G3 Domain Regulates Neurite Growth and Synaptic Transmission of Hippocampal Neurons by Activation of Epidermal Growth Factor Receptor

Versican is one of the major extracellular matrix (ECM) proteins in the brain. ECM molecules and their cleavage products critically regulate the growth and arborization of neurites, hence adjusting the formation of neural networks. Recent findings have revealed that peptide fragments containing the versican C terminus (G3 domain) are present in human brain astrocytoma. The present study demonstrated that a versican G3 domain enhanced cell attachment, neurite growth, and glutamate receptor-mediated currents in cultured embryonic hippocampal neurons. In addition, the G3 domain intensified dendritic spines, increased the clustering of both synaptophysin and the glutamate receptor subunit GluR2, and augmented excitatory synaptic activity. In contrast, a mutated G3 domain lacking the epidermal growth factor (EGF)-like repeats (G3deltaEGF) had little effect on neurite growth and glutamatergic function. Treating the neurons with the G3-conditioned medium rapidly increased the levels of phosphorylated EGF receptor (pEGFR) and phosphorylated extracellular signal-regulated kinase (pERK), indicating an activation of EGFR-mediated signaling pathways. Blockade of EGFR prevented the G3-induced ERK activation and suppressed the G3-provoked enhancement of neurite growth and glutamatergic function but failed to block the G3-mediated enhancement of cell attachment. These combined results indicate that the versican G3 domain regulates neuronal attachment, neurite outgrowth, and synaptic function of hippocampal neurons via EGFR-dependent and -independent signaling pathway(s). Our findings suggest a role for ECM proteolytic products in neural development and regeneration.

PPARγ‐regulated tight junction development during human urothelial cytodifferentiation

Urothelial barrier function is maintained by apical membrane plaques and intercellular tight junctions (TJ). Little is known about the composition and regulation of TJ expression in human urothelium. In this study, we have characterised the expression of TJ components in situ and their regulation in an in vitro model of differentiating normal human urothelial (NHU) cells. In normal ureteric urothelium in situ, there was a differentiation-associated profile of claudins 3, 4, 5, 7, ZO1 and occludin proteins. Proliferating NHU cells in vitro expressed predominantly claudin 1 protein and transcripts for claudins 1-5 and 7. Following induction of differentiation by pharmacological activation of PPARgamma and blockade of EGFR, there was de novo expression of claudin 3 mRNA and protein and downregulation of claudin 2 transcription. There was also a massive increase in expression of claudin 4 and 5 proteins which was due to inhibition of proteasomal degradation of claudin 4 and consequential stabilisation of the claudin 5 heterodimerisation partner. NHU cell differentiation was accompanied by relocalisation of TJ proteins to intercellular junctions. The differentiation-associated development of TJ formation in vitro reflected the stage-related TJ expression seen in situ. This was distinct from changes in TJ composition of NHU cells mediated by increasing the calcium concentration of the medium. Our results imply a role for PPARgamma and EGFR signalling pathways in regulating TJ formation in NHU cells and support the hypothesis that TJ development is an integral part of the urothelial differentiation programme.

Enhancement of tumor radioresponse by combined treatment with gefitinib (Iressa, ZD1839), an epidermal growth factor receptor tyrosine kinase inhibitor, is accompanied by inhibition of DNA damage repair and cell growth in oral cancer.

Molecular blockade of EGFR with either an EGFR MAb or an EGFR TKI enhances the radiosensitivity of human SCCs. In the present study, we investigated whether treatment with the EGFR TKI gefitinib (Iressa, ZD1839) improves the response to radiotherapy in the OSCC cell lines HSC2 and HSC3. We examined potential mechanisms that may contribute to the enhanced radiation response induced by gefitinib. Growth inhibition was observed in vitro with radiation or gefitinib. A cooperative antiproliferative effect was obtained when cancer cells were treated with radiation followed by gefitinib. Cells treated with a combination of radiation and gefitinib arrested in G(1) and G(2)-M phases, with a decrease in the S-phase population. While radiation alone did not significantly affect MEK1/2 and p38 MAPK autophosphorylation, the combination of gefitinib and radiation completely inhibited the downstream signaling of EGFR. Results from DNA damage repair analysis in cultured OSCC cells demonstrated that gefitinib had a strong inhibitory effect on DNA-PKc pathways after radiation. Tumor xenograft studies demonstrated that the combination of gefitinib and radiation caused growth inhibition and tumor regression of well-established OSCC tumors in athymic mice; tumor volume was reduced from 1,008.2 to 231.4 mm(3) in HSC2 cells (p < 0.01) and from 284.2 to 12.4 mm(3) in HSC3 cells (p < 0.01). Immunohistochemical analysis of OSCC xenografts revealed that gefitinib caused a striking decrease in tumor cell proliferation when combined with radiotherapy. Overall, we conclude that gefitinib enhances tumor radioresponse by multiple mechanisms that may involve antiproliferative growth inhibition and effects on DNA repair after exposure to radiation.