Near-Infrared Photoimmunotherapy Using a Protein Mimetic for EGFR-Positive Salivary Gland Cancer.

Near-infrared photoimmunotherapy (NIR-PIT) is a novel cancer therapy based on a monoclonal antibody (mAb) conjugated to a photosensitizer (IR700Dye). The conjugate can be activated by near-infrared light irradiation, causing necrotic cell death with high selectivity. In this study, we investigated NIR-PIT using a small protein mimetic (6-7 kDa, Affibody) which has more rapid clearance and better tissue penetration than mAbs for epidermal growth factor receptor (EGFR)-positive salivary gland cancer (SGC). The level of EGFR expression was examined in vitro using immunocytochemistry and Western blotting. Cell viability was analyzed using the alamarBlue assay. In vivo, the volume of EGFR-positive tumors treated with NIR-PIT using the EGFR Affibody-IR700Dye conjugate was followed for 43 days. It was found that NIR-PIT using the EGFR Affibody-IR700Dye conjugate induced the selective destruction of EGFR-positive SGC cells and restricted the progression of EGFR-positive tumors. We expect that NIR-PIT using the EGFR Affibody-IR700Dye conjugate can efficiently treat EGFR-positive SGC and preserve normal salivary function.

Combination of Near-Infrared Photoimmunotherapy Using Trastuzumab and Small Protein Mimetic for HER2-Positive Breast Cancer.

Near-infrared photoimmunotherapy (NIR-PIT) is a promising cancer therapy based on a monoclonal antibody conjugated to a photosensitizer (IR700Dye) that is activated by near-infrared light irradiation. We previously reported on the use of NIR-PIT with a small protein mimetic, the Affibody molecule (6-7 kDa), instead of a monoclonal antibody. In this study, we investigated a combination of NIR-PIT for HER2-positive breast cancer cells (SK-BR3, MDA-MB361, and JIMT1) with HER2 Affibody-IR700Dye conjugate and trastuzumab-IR700Dye conjugate. HER2 Affibody and trastuzumab target different epitopes of the HER2 protein and do not compete. In vitro, the combination of NIR-PIT using both HER2 Affibody-IR700Dye conjugate and trastuzumab-IR700Dye conjugate induced necrotic cell death of HER2-positive breast cancer cells without damage to HER2-negative breast cancer cells (MCF7). It was more efficient than NIR-PIT using either the HER2 Affibody-IR700Dye conjugate alone or the trastuzumab-IR700Dye conjugate alone. Additionally, this combination of NIR-PIT was significantly effective against HER2 low-expressing cancer cells, trastuzumab-resistant cells (JIMT1), and brain metastatic cells of breast cancer (MDA-MB361). Furthermore, in vivo imaging exhibited the strong fluorescence intensity of both HER2 Affibody-IR700Dye conjugates and trastuzumab-Alexa488 conjugates in HER2-positive tumor, indicating that both HER2 Affibody and trastuzumab specifically bind to HER2-positive tumors without competing with each other. In conclusion, the combination of NIR-PIT using both HER2 Affibody and trastuzumab expands the targeting scope of NIR-PIT for HER2-positive breast cancer.

Developmental Process of a Heterozooid: Avicularium Formation in a Bryozoan, Bugulina californica.

In bryozoans (phylum Bryozoa), representative colonial animals mostly found in marine environments, some species possess different types of individuals (heterozooids) specialized in different functions such as defense or structural support for their colonies. Among them, the best-known heterozooids are the avicularia, known to function as defenders. The differentiation processes of heterozooids, including avicularia, should be important keys to understand the evolutionary significance of bryozoans. However, the developmental process of avicularium formation remains to be fully understood. In this study, therefore, in order to understand the detailed developmental process and timing of avicularium formation, extensive observations were carried out in a bryozoan species, Bugulina californica (Cheilostomata, Bugulidae), that possesses adventitious avicularia, by performing stereomicroscopy on live materials, in addition to scanning electron microscopy and histological observations. The whole process can be divided into seven stages based on developmental events. Especially notably, at the earlier stages, there are three major budding events that produce proliferating cell masses corresponding to primordial tissues: (1) budding of the peduncle cushion at the outer margin of the distal part of a young autozooid, (2) budding of the head-part primordium from the peduncle cushion, and (3) budding of the polypide inside the head part. Experimental control of temperature showed that 20°C would be the best to maintain B. californica colonies.

Near-Infrared Photoimmunotherapy Using a Small Protein Mimetic for HER2-Overexpressing Breast Cancer.

Near-infrared photoimmunotherapy (NIR-PIT) is a new and promising cancer therapy based on a monoclonal antibody conjugated to a photosensitizer which is activated by near-infrared light irradiation, causing cell death. We investigated NIR-PIT using a small protein mimetic (6-7 kDa), Affibody molecules, instead of a monoclonal antibody for HER2-overexpressing cancer. Because of its small size, the Affibody has rapid clearance, high imaging contrast, and good tumor penetration. Due to the small size of the Affibodies, which can cross the blood-brain barrier, NIR-PIT using Affibodies has the potential to extend the target cancer of NIR-PIT, including brain metastases. In vitro, NIR-PIT using HER2 Affibody-IR700Dye conjugates induced the selective destruction of HER2-overexpressing breast cancer cells without damage to control cells having low level expression of HER2. HER2-overexpressing cancer cells showed necrotic cell death and their viability maintained at low levels, even 5 days after NIR-PIT. In contrast, treatment with high concentration of HER2 Affibody-IR700Dye conjugate alone or irradiation with high dose of NIR light alone was without effect on cell viability. Affibody and IR700Dye are currently used clinically, and therefore, we would expect the current formulation to be safely and quickly transitioned into clinical trials.

Imaging of Metastatic Cancer Cells in Sentinel Lymph Nodes using Affibody Probes and Possibility of a Theranostic Approach.

The accurate detection of lymph node metastases is essential for treatment success in early-stage malignant cancer. Sentinel lymph node (SLN) biopsy is the most effective procedure for detecting small or micrometastases that are undetectable by conventional imaging modalities. To demonstrate a new approach for developing a more efficient SLN biopsy procedure, we reported a two-stage imaging method combining lymphoscintigraphy and near-infrared (NIR) fluorescence imaging to depict metastatic cancer cells in SLNs in vivo. Furthermore, the theranostic potential of the combined procedure was examined by cell culture and xenograft mouse model. Anti-HER2 and anti-epidermal growth factor receptor (EGFR) affibody probes were used for NIR fluorescence imaging. Strong NIR fluorescence signal intensity of the anti-EGFR affibody probe was observed in SAS cells (EGFR positive). Radioactivity in the SLNs was clearly observed in the in vivo studies. High anti-EGFR affibody NIR fluorescence intensity was observed in the metastatic lymph nodes in mice. The addition of the IR700-conjugated anti-EGFR affibody to the culture medium decreased the proliferation of SAS cells. Decreased proliferation was shown in Ki-67 immunohistochemistry in xenograft tumors. Our data suggest that a two-stage combined imaging method using lymphoscintigraphy and affibody probes may offer the direct visualization of metastatic lymph nodes as an easily applied technique in SLN biopsy. Although further animal studies are required to assess the effect of treating lymphatic metastasis in this approach, our study results provide a foundation for the further development of this promising imaging and treatment strategy for earlier lymph node metastasis detection and treatment.

HER2-Targeted Multifunctional Silica Nanoparticles Specifically Enhance the Radiosensitivity of HER2-Overexpressing Breast Cancer Cells.

We investigated the effects of targeted functionalized silica nanoparticles on the radiosensitivity of cancer cells. Better control of the local concentration of silica nanoparticles may facilitate their use as an adjuvant in conjunction with ionizing radiation to target cancer cells while preventing damage to normal cells. Hyperbranched polyamidoamine (PAMAM) was grafted onto the surface of amorphous silica nanoparticles to functionalize them. The PAMAM-coated silica nanoparticles (PCSNs) were then conjugated with fluorescent dyes. Anti-HER2 antibodies were covalently attached to the labeled PCSNs. The HER2-overexpressing SK-BR3 breast cancer cell line was incubated in medium containing the PCSN probes. After incubation; the cells were exposed to X-ray radiation. Cells were counted in all samples using cell proliferation assays; and apoptotic cells were detected. The cell survival results showed that the combination of the targeted PCSN probes and radiation reduced the survival rate of SK-BR3 cells to a greater extent than when either PCSN probes, PCSNs or radiation were applied individually. The results also showed an increase in apoptosis in the SK-BR3 cells that internalized the PCSN probes and were then irradiated. Based on these data, PCSN probes act as specific radiosensitizing agents for HER2-overexpressing cells.

A20 restores phorbol ester-induced differentiation of THP-1 cells in the absence of nuclear factor-κB activation.

A20, also referred to as tumor necrosis factor alpha (TNFα)-induced protein 3 (TNFAIP3), is an ubiquitin-editing enzyme whose expression is enhanced by NF-κB activation, and plays an important role in silencing NF-κB activity. Another well-known role for A20 is to protect cells from TNFα-induced apoptosis. Depletion of NF-κB in differentiating U937 monocytic leukemia cells is known to cause apoptotic cell death; however, much remains to be explored about the molecules that are expressed in an NF-κB-dependent manner and which support monocyte-macrophage differentiation. Using the monocytic cell line THP-1, and peripheral blood monocytes, we show here a sustained increase in A20 expression during monocyte-macrophage differentiation, which coincided with high NF-κB-dependent transcriptional activity. Depletion of NF-κB by stable expression of a super-repressor form of IκBα in THP-1 cells caused remarkable cell death during phorbol 12-myristate 13-acetate (PMA)-induced differentiation. A20 expression in these cells did not alter this NF-κB suppression, but was sufficient to protect the cells and restore the cell surface expression of a differentiation marker (CD11b) and phagocytic activity. Mutational analyses revealed that this A20 activity requires the carboxy-terminal zinc-finger domain, but not its deubiquitinase activity. Based on these findings, we conclude that A20, when ectopically expressed, can support both survival and differentiation of THP-1 cells in the absence of sustained NF-κB activity.

Structural Variations in Parotid Glands Induced by Radiation Therapy in Patients with Oral Carcinoma Observed on Contrast-Enhanced Computed Tomography.

BACKGROUND: Xerostomia is one of the commonest radiation-induced complications in patients with head and neck carcinoma. The aim of this study was to assess structural variations in parotid glands induced by radiation therapy in patients with oral carcinoma with contras-enhanced computed tomography (CECT). MATERIAL/METHODS: A retrospective study was performed in 41 patients with oral carcinoma who underwent CECT for head and neck malignancies before and after radiotherapy. We analyzed the relationship between parotid density variations, parotid volume change, as seen on CECT, and the mean radiation dose applied to the parotid glands in patients with oral carcinoma immediately after radiotherapy, and 2 and 3 years later. RESULTS: Immediately after radiotherapy, high-density changes on contrast-enhanced CT were observed in 70.5% of the irradiated parotids. Low-density changes due to fat degeneration were seen in 46.2% and 72.2% of the irradiated parotids 2 and 3 years after radiotherapy, respectively. The mean dose applied to the parotids with the low-density changes and without such changes 3 years after radiotherapy was 46.0 Gy and 27.7 Gy, respectively (p=0.049). Furthermore, parotid shrinkage was observed in 63.6% of the irradiated parotids. CONCLUSIONS: This study suggests that the structural variations in parotid glands induced by radiotherapy included high-density changes that were observed immediately after radiotherapy and low-density changes that were seen at late follow-up. This study should be useful for clinicians in the assessment of radiation-induced injuries in the parotids with respect to early prediction of xerostomia.

Dual-Labeled Near-Infrared/(99m)Tc Imaging Probes Using PAMAM-Coated Silica Nanoparticles for the Imaging of HER2-Expressing Cancer Cells.

We sought to develop dual-modality imaging probes using functionalized silica nanoparticles to target human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer cells and achieve efficient target imaging of HER2-expressing tumors. Polyamidoamine-based functionalized silica nanoparticles (PCSNs) for multimodal imaging were synthesized with near-infrared (NIR) fluorescence (indocyanine green (ICG)) and technetium-99m ((99m)Tc) radioactivity. Anti-HER2 antibodies were bound to the labeled PCSNs. These dual-imaging probes were tested to image HER2-overexpressing breast carcinoma cells. In vivo imaging was also examined in breast tumor xenograft models in mice. SK-BR3 (HER2 positive) cells were imaged with stronger NIR fluorescent signals than that in MDA-MB231 (HER2 negative) cells. The increased radioactivity of the SK-BR3 cells was also confirmed by phosphor imaging. NIR images showed strong fluorescent signals in the SK-BR3 tumor model compared to muscle tissues and the MDA-MB231 tumor model. Automatic well counting results showed increased radioactivity in the SK-BR3 xenograft tumors. We developed functionalized silica nanoparticles loaded with (99m)Tc and ICG for the targeting and imaging of HER2-expressing cells. The dual-imaging probes efficiently imaged HER2-overexpressing cells. Although further studies are needed to produce efficient isotope labeling, the results suggest that the multifunctional silica nanoparticles are a promising vehicle for imaging specific components of the cell membrane in a dual-modality manner.

Micro-CT evaluation of high pressure-decellularized cardiovascular tissues transplanted in rat subcutaneous accelerated-calcification model.

We have succeeded in reducing the calcification of acellular aortas or valves in porcine allogeneic system by removing the DNA and phospholipids, but its further reduction is desirable. Here, the calcification of the acellular tissue was evaluated in rat subcutaneous transplantation model which is known as calcification model. Acellular samples prepared by high-hydrostatic pressure (HHP) protocols with different washing media were implanted and the calcification was monitored under micro-computed tomography for 1 and 3 months. The amount of the calcium deposition was quantitatively evaluated by atomic absorption spectroscopy. A cell culture medium showed very good cell removal ability but led to severe calcification at 1 month, and surprisingly the calcium deposition increased as the washing period increased. This calcification was suppressed by removing the DNA fraction with high DNase concentration. On the other hand, the calcification was greatly reduced when washed with saline even at low DNase concentration after 2 weeks washing. These results suggest that the ion species in the washing medium and the residual DNase cooperatively affect the tendency of in vivo calcification, which led us to the possibility of reduced calcification of acellular cardiac tissues.

Tyrosine phosphoproteomics identifies both codrivers and cotargeting strategies for T790M-related EGFR-TKI resistance in non-small cell lung cancer.

PURPOSE: Irreversible EGFR-tyrosine kinase inhibitors (TKI) are thought to be one strategy to overcome EGFR-TKI resistance induced by T790M gatekeeper mutations in non-small cell lung cancer (NSCLC), yet they display limited clinical efficacy. We hypothesized that additional resistance mechanisms that cooperate with T790M could be identified by profiling tyrosine phosphorylation in NSCLC cells with acquired resistance to reversible EGFR-TKI and harboring T790M. EXPERIMENTAL DESIGN: We profiled PC9 cells with TKI-sensitive EGFR mutation and paired EGFR-TKI-resistant PC9GR (gefitinib-resistant) cells with T790M using immunoaffinity purification of tyrosine-phosphorylated peptides and mass spectrometry-based identification/quantification. Profiles of erlotinib perturbations were examined. RESULTS: We observed a large fraction of the tyrosine phosphoproteome was more abundant in PC9- and PC9GR-erlotinib-treated cells, including phosphopeptides corresponding to MET, IGF, and AXL signaling. Activation of these receptor tyrosine kinases by growth factors could protect PC9GR cells against the irreversible EGFR-TKI afatinib. We identified a Src family kinase (SFK) network as EGFR-independent and confirmed that neither erlotinib nor afatinib affected Src phosphorylation at the activation site. The SFK inhibitor dasatinib plus afatinib abolished Src phosphorylation and completely suppressed downstream phosphorylated Akt and Erk. Dasatinib further enhanced antitumor activity of afatinib or T790M-selective EGFR-TKI (WZ4006) in proliferation and apoptosis assays in multiple NSCLC cell lines with T790M-mediated resistance. This translated into tumor regression in PC9GR xenograft studies with combined afatinib and dasatinib. CONCLUSIONS: Our results identified both codrivers of resistance along with T790M and support further studies of irreversible or T790M-selective EGFR inhibitors combined with dasatinib in patients with NSCLC with acquired T790M.

MET amplification as a potential therapeutic target in gastric cancer.

Our aim was to investigate both the prevalence of MET amplification in gastric cancer as well as the potential of this genetic alteration to serve as a therapeutic target in gastric cancer. MET amplification was assessed by initial screening with a PCR-based copy number assay followed by confirmatory FISH analysis in formalin-fixed, paraffin-embedded specimens of gastric cancer obtained at surgery. The effects of MET tyrosine kinase inhibitors (MET-TKIs) in gastric cancer cells with or without MET amplification were also examined. The median MET copy number in 266 cases of gastric cancer was 1.7, with a range of 0.41 to 21.3. We performed FISH analysis for the 15 cases with the highest MET copy numbers. MET amplification was confirmed in the four assessable cases with a MET copy number of at least 4, whereas MET amplification was not detected in those with a gene copy number of less than 4. The prevalence of MET amplification was thus 1.5% (4 out of 266 cases). Inhibition of MET by MET-TKIs resulted in the induction of apoptosis accompanied by attenuation of downstream MET signaling in gastric cancer cell lines with MET amplification but not in those without this genetic change. MET amplification identifies a small but clinically important subgroup of gastric cancer patients who are likely to respond to MET-TKIs. Furthermore, screening with a PCR-based copy number assay is an efficient way to reduce the number of patients requiring confirmation of MET amplification by FISH analysis.

Activation of HER family signaling as a mechanism of acquired resistance to ALK inhibitors in EML4-ALK-positive non-small cell lung cancer.

PURPOSE: Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKI) such as crizotinib show marked efficacy in patients with non-small cell lung cancer positive for the echinoderm microtubule-associated protein-like 4 (EML4)-ALK fusion protein. However, acquired resistance to these agents has already been described in treated patients, and the mechanisms of such resistance remain largely unknown. EXPERIMENTAL DESIGN: We established lines of EML4-ALK-positive H3122 lung cancer cells that are resistant to the ALK inhibitor TAE684 (H3122/TR cells) and investigated their resistance mechanism with the use of immunoblot analysis, ELISA, reverse transcription and real-time PCR analysis, and an annexin V binding assay. We isolated EML4-ALK-positive lung cancer cells (K-3) from a patient who developed resistance to crizotinib and investigated their characteristics. RESULTS: The expression of EML4-ALK was reduced at the transcriptional level, whereas phosphorylation of epidermal growth factor receptor (EGFR), HER2, and HER3 was upregulated, in H3122/TR cells compared with those in H3122 cells. This activation of HER family proteins was accompanied by increased secretion of EGF. Treatment with an EGFR-TKI induced apoptosis in H3122/TR cells, but not in H3122 cells. The TAE684-induced inhibition of extracellular signal-regulated kinase (ERK) and STAT3 phosphorylation observed in parental cells was prevented by exposure of these cells to exogenous EGF, resulting in a reduced sensitivity of cell growth to TAE684. K-3 cells also manifested HER family activation accompanied by increased EGF secretion. CONCLUSIONS: EGF-mediated activation of HER family signaling is associated with ALK-TKI resistance in lung cancer positive for EML4-ALK.

Antitumor action of the MET tyrosine kinase inhibitor crizotinib (PF-02341066) in gastric cancer positive for MET amplification.

Therapeutic strategies that target the tyrosine kinase MET hold promise for gastric cancer, but the mechanism underlying the antitumor activity of such strategies remains unclear. We examined the antitumor action of the MET tyrosine kinase inhibitor crizotinib (PF-02341066) in gastric cancer cells positive or negative for MET amplification. Inhibition of MET signaling by crizotinib or RNA interference-mediated MET depletion resulted in induction of apoptosis accompanied by inhibition of AKT and extracellular signal-regulated kinase phosphorylation in gastric cancer cells with MET amplification but not in those without it, suggesting that MET signaling is essential for the survival of MET amplification-positive cells. Crizotinib upregulated the expression of BIM, a proapoptotic member of the Bcl-2 family, as well as downregulated that of survivin, X-linked inhibitor of apoptosis protein (XIAP), and c-IAP1, members of the inhibitor of apoptosis protein family, in cells with MET amplification. Forced depletion of BIM inhibited crizotinib-induced apoptosis, suggesting that upregulation of BIM contributes to the proapoptotic effect of crizotinib. Crizotinib also exhibited a marked antitumor effect in gastric cancer xenografts positive for MET amplification, whereas it had little effect on those negative for this genetic change. Crizotinib thus shows a marked antitumor action both in vitro and in vivo specifically in gastric cancer cells positive for MET amplification.

Overcoming erlotinib resistance in EGFR mutation-positive non-small cell lung cancer cells by targeting survivin.

Loss of PTEN was recently shown to contribute to resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) in EGFR mutation-positive non-small cell lung cancer (NSCLC) through activation of the protein kinase AKT. We previously showed that downregulation of the expression of the antiapoptotic protein survivin by EGFR-TKIs contributes to EGFR-TKI-induced apoptosis in EGFR mutation-positive NSCLC cells. We have now investigated the role of survivin expression in EGFR-TKI resistance induced by PTEN loss. The EGFR-TKI erlotinib did not affect survivin expression or induce apoptosis in EGFR mutation-positive NSCLC cells with PTEN loss. Downregulation of survivin either by transfection with a specific short interfering RNA or by exposure to the small-molecule survivin suppressor YM155 reversed erlotinib resistance in such cells in vitro. Furthermore, combination therapy with YM155 and erlotinib inhibited the growth of tumors formed by EGFR mutation-positive, PTEN-deficient NSCLC cells in nude mice to a greater extent than did treatment with either drug alone. These results thus indicate that persistent activation of signaling by the AKT-survivin pathway induced by PTEN loss underlies a mechanism of resistance to erlotinib-induced apoptosis in EGFR mutation-positive NSCLC. They further suggest that the targeting of survivin has the potential to overcome EGFR-TKI resistance in EGFR mutation-positive NSCLC.

MET tyrosine kinase inhibitor crizotinib (PF-02341066) shows differential antitumor effects in non-small cell lung cancer according to MET alterations.

INTRODUCTION: Tyrosine kinase inhibitors (TKIs) targeted to MET are undergoing clinical trials in patients with solid tumors, but the precise mechanism of the antitumor activity of these drugs remains unclear. We examined the antitumor action of the MET-TKI crizotinib (PF-02341066) in lung cancer cells that are positive or negative for MET amplification or mutation. METHODS: The antitumor action of crizotinib was evaluated on the basis of signal transduction, cell proliferation, apoptosis, and progression of tumor xenografts. RESULTS: Inhibition of MET signaling by crizotinib or by RNA interference-mediated MET depletion resulted in the induction of apoptosis accompanied by inhibition of AKT and extracellular signal-regulated kinase phosphorylation in lung cancer cells with MET amplification but not in cells with a MET mutation or in those without amplification or mutation of MET. These results suggest that MET signaling is essential for the survival of cells with MET amplification but not for that of cells without this genetic change, including those with a MET mutation. Crizotinib up-regulated the expression of BIM, a proapoptotic member of the Bcl-2 family, and down-regulated that of survivin, a member of the inhibitor of apoptosis protein family, in cells with MET amplification. Forced depletion of BIM and expression of survivin each inhibited crizotinib-induced apoptosis, suggesting that both up-regulation of BIM and down-regulation of survivin contribute to the proapoptotic effect of crizotinib. CONCLUSIONS: Crizotinib shows a marked antitumor action in MET amplification-positive lung cancer cells but not in cells without MET amplification, including those with a MET mutation.

Role of survivin in EGFR inhibitor-induced apoptosis in non-small cell lung cancers positive for EGFR mutations.

The molecular mechanism by which epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) induce apoptosis in non-small cell-lung cancer (NSCLC) cells that are positive for activating mutations of the EGFR remains unclear. In this study, we report the effects of the EGFR-TKI gefitinib on expression of the antiapoptotic protein survivin that have functional consequences in EGFR mutation-positive NSCLC cells. Immunoblot analysis revealed that gefitinib downregulated survivin expression, likely through inhibition of the PI3K-AKT signaling pathway, in NSCLC cells positive for EGFR mutation. Stable overexpression of survivin attenuated gefitinib-induced apoptosis and also inhibited the antitumor effect of gefitinib in human tumor xenografts. Furthermore, the combination of survivin overexpression with inhibition of the gefitinib-induced upregulation of the proapoptotic protein BIM attenuated gefitinib-induced apoptosis to a greater extent than either approach alone. Our results indicate that downregulation of survivin plays a pivotal role in gefitinib-induced apoptosis in EGFR mutation-positive NSCLC cells. Furthermore, they suggest that simultaneous interruption of the PI3K-AKT-survivin and MEK-ERK-BIM signaling pathways is responsible for EGFR-TKI-induced apoptotic death in these cells.

TAK-701, a humanized monoclonal antibody to hepatocyte growth factor, reverses gefitinib resistance induced by tumor-derived HGF in non-small cell lung cancer with an EGFR mutation.

Most non-small cell lung cancer (NSCLC) tumors with an activating mutation of the epidermal growth factor receptor (EGFR) are initially responsive to EGFR tyrosine kinase inhibitors (TKI) such as gefitinib but ultimately develop resistance to these drugs. Hepatocyte growth factor (HGF) induces EGFR-TKI resistance in NSCLC cells with such a mutation. We investigated strategies to overcome gefitinib resistance induced by HGF. Human NSCLC cells with an activating EGFR mutation (HCC827 cells) were engineered to stably express HGF (HCC827-HGF cells). HCC827-HGF cells secreted large amounts of HGF and exhibited resistance to gefitinib in vitro to an extent similar to that of HCC827 GR cells, in which the gene for the HGF receptor MET is amplified. A MET-TKI reversed gefitinib resistance in HCC827-HGF cells as well as in HCC827 GR cells, suggesting that MET activation induces gefitinib resistance in both cell lines. TAK-701, a humanized monoclonal antibody to HGF, in combination with gefitinib inhibited the phosphorylation of MET, EGFR, extracellular signal-regulated kinase, and AKT in HCC827-HGF cells, resulting in suppression of cell growth and indicating that autocrine HGF-MET signaling contributes to gefitinib resistance in these cells. Combination therapy with TAK-701 and gefitinib also markedly inhibited the growth of HCC827-HGF tumors in vivo. The addition of TAK-701 to gefitinib is a promising strategy to overcome EGFR-TKI resistance induced by HGF in NSCLC with an activating EGFR mutation.

Enhanced anticancer effect of the combination of BIBW2992 and thymidylate synthase-targeted agents in non-small cell lung cancer with the T790M mutation of epidermal growth factor receptor.

Most non-small cell lung cancer (NSCLC) tumors with activating mutations of the epidermal growth factor receptor (EGFR) are initially responsive to first-generation, reversible EGFR tyrosine kinase inhibitors (TKI) such as gefitinib, but they subsequently develop resistance to these drugs through either acquisition of an additional T790M mutation of EGFR or amplification of the proto-oncogene MET. We have now investigated the effects of combination treatment with thymidylate synthase (TS)-targeting drugs and the second-generation, irreversible EGFR-TKI BIBW2992 on the growth of NSCLC cells with the T790M mutation. The effects of BIBW2992 on EGFR signaling and TS expression in gefitinib-resistant NSCLC cells were examined by immunoblot analysis. The effects of BIBW2992 and the TS-targeting agents S-1 (or 5-fluorouracil) or pemetrexed on the growth of gefitinib-resistant NSCLC cells were examined both in vitro and in vivo. The combination of BIBW2992 with 5-fluorouracil or pemetrexed synergistically inhibited the proliferation of NSCLC cells with the T790M mutation in vitro, whereas an antagonistic interaction was apparent in this regard between gefitinib and either of these TS-targeting agents. BIBW2992 induced downregulation of TS in the gefitinib-resistant NSCLC cells, implicating depletion of TS in the enhanced antitumor effect of the combination therapy. The combination of BIBW2992 and either the oral fluoropyrimidine S-1 or pemetrexed also inhibited the growth of NSCLC xenografts with the T790M mutation to an extent greater than that apparent with either agent alone. The addition of TS-targeting drugs to BIBW2992 is a promising strategy to overcome EGFR-TKI resistance in NSCLC with the T790M mutation of EGFR.