Gefitinib (Iressa, ZD1839) inhibits SN38-triggered EGF signals and IL-8 production in gastric cancer cells

An emerging role of N-glycosylation in cancer chemoresistance

Chemoresistance poses a significant obstacle in the effective treatment of cancer, limiting the success of chemotherapy regimens. N-glycosylation, the most important post-translational modification (PTM), plays multifaceted roles in the intricate landscape of cancer progression, particularly drug resistance in cancer cells. This review explores the complex relationship between N-glycosylation and chemoresistance in cancer. Altered glycosylation patterns have been proven to impact drug efflux mechanisms in cancer cells, which can further influence the intracellular concentration of chemotherapy drugs. Moreover, N-glycosylation also plays a regulatory role in cell signaling pathways and apoptosis regulators, continuously affecting the stemness and survival of cancer cells under the selective pressure of chemotherapy. Additionally, the impact of the tumor microenvironment on glycosylation patterns adds complexity to this interplay. This review discusses current research findings, challenges, and future directions based on the roles of N-glycosylation in cancer chemoresistance, emphasizing the potential for targeted therapeutic interventions to enhance the effectiveness of chemotherapy and improve patient outcomes.

Treatment with S-adenosylmethionine ameliorates irinotecan-induced intestinal barrier dysfunction and intestinal microbial disorder in mice

This study aimed to investigate the protective effects of S-adenosylmethionine (SAM) on irinotecan-induced intestinal barrier dysfunction and microbial ecological dysregulation in both mice and human colon cell line Caco-2, which is widely used for studying intestinal epithelial barrier function. Specifically, this study utilized Caco-2 monolayers incubated with 7-ethyl-10-hydroxycamptothecin (SN-38) as well as an irinotecan-induced diarrhea model in mice. Our study found that SAM pretreatment significantly reduced body weight loss and diarrhea induced by irinotecan in mice. Furthermore, SAM inhibited the increase of intestinal permeability in irinotecan-treated mice and ameliorated the decrease of Zonula occludens-1(ZO-1), Occludin, and Claudin-1 expression. Additionally, irinotecan treatment increased the relative abundance of Proteobacteria compared to the control group, an effect that was reversed by SAM administration. In Caco-2 monolayers, SAM reduced the expression of reactive oxygen species (ROS) and ameliorated the decrease in transepithelial electrical resistance (TER) and increase in fluorescein isothiocyanate-dextran 4000 Da (FD-4) flux caused by SN-38. Moreover, SAM attenuated changes in the localization and distribution of ZO-1and Occludin in Caco-2 monolayers induced by SN-38 and protected barrier function by inhibiting activation of the p38 MAPK/p65 NF-κB/MLCK/MLC signaling pathway. These findings provide preliminary evidence for the potential use of SAM in treating diarrhea caused by irinotecan.

EGFR Blockade Reverses Cisplatin Resistance in Human Epithelial Ovarian Cancer Cells

Background:

EOC is one of the most lethal gynecological malignancy worldwide. Although the majority of EOC patients achieve clinical remission after induction therapy, over 80% relapse and succumb to the chemoresistant disease. Previous investigations have demonstrated the association of EGFR with resistance to cytotoxic chemotherapies, hormone therapy, and radiotherapy in the cancers. These studies have highlighted the role of EGFR as an attractive therapeutic target in cisplatin-resistant EOC cells.

Methods:

The human ovarian cell lines (SKOV3 and OVCAR3) were cultured according to ATCC recommendations. The MTT assay was used to determine the chemosensitivity of the cell lines in exposure to cisplatin and erlotinib. The qRT-PCR was applied to analyze the mRNA expression of the desired genes.

Results:

Erlotinib in combination with cisplatin reduced the cell proliferation in the chemoresistant EOC cells in comparison to monotherapy of the drugs (p < 0.05). Moreover, erlotinib/cisplatin combination synergistically decreased the expression of anti-apoptotic and also increased pro-apoptotic genes expression (p < 0.05). Cisplatin alone could increase the expression of MDR genes. The data suggested that EGFR and cisplatin drive chemoresistance in the EOC cells through MEKK signal transduction as well as through EGFR/MEKK pathways in the cells, respectively.

Conclusion:

Our findings propose that EGFR is an attractive therapeutic target in chemoresistant EOC to be exploited in translational oncology, and erlotinib/cisplatin combination treatment is a potential anti-cancer approach to overcome chemoresistance and inhibit the proliferation of the EOC cells.

Inhibitory effects of genistein in combination with gefitinib on the hepatocellular carcinoma Hep3B cell line

Combination therapy is an important method for treating advanced hepatocellular carcinoma (HCC). Gefitinib is an epidermal growth factor receptor (EGFR) inhibitor, which has profound effects on HCC. The purpose of the present study was to investigate the effects of genistein in combination with gefitinib on the proliferation and apoptosis of HCC cells and the associated mechanism. Cell counting kit-8 assay was performed to calculate the IC₅₀ values and cytotoxicity, whilst flow cytometry was used to assess cell apoptosis. Protein expression was detected using western blot analysis. The IC₅₀ of genistein and gefitinib on Hep3B cells were calculated to be 128.078 and 13.657 µM, respectively. Genistein in combination with gefitinib significantly inhibited cell viability, promoted apoptosis and reduced EGFR, vascular endothelial growth factor receptor and platelet-derived growth factor receptor phosphorylation. Genistein in combination with gefitinib promoted the expression of cleaved caspase-3 and cleaved poly ADP-ribose polymerase. In addition, combined treatment of genistein and gefitinib strongly inhibited the activation of the Akt/Erk/mTOR signaling pathway. In conclusion, findings from the present study suggest that genistein in combination with gefitinib inhibit HCC cell proliferation and promote apoptosis by inhibiting the Akt/Erk/mTOR pathway.

Tumor progression-dependent angiogenesis in gastric cancer and its potential application

Despite improvements in the early diagnosis, prognosis and therapeutic strategies for gastric cancer (GC), human GC remains one of the most frequently diagnosed malignant tumors in the world, and the survival rate of GC patients remains very poor. Thus, a suitable therapeutic strategy for GC is important for prolonging survival. Both tumor cells themselves and the tumor microenvironment play an important role in tumorigenesis, including angiogenesis, inflammation, immunosuppression and metastasis. Importantly, these cells contribute to gastric carcinogenesis by altering the angiogenic phenotype switch. The development, relapse and spreading of tumors depend on new vessels that provide the nutrition, growth factors and oxygen required for continuous tumor growth. Therefore, a state of tumor dormancy could be induced by blocking tumor-associated angiogenesis. Recently, several antiangiogenic agents have been identified, and their potential for the clinical management of GC has been tested. Here, we provide an up-to-date summary of angiogenesis and the angiogenic factors associated with tumor progression in GC. We also review antiangiogenic agents with a focus on the anti-vascular endothelial growth factor receptor (VEGFR)-mediated pathway for endothelial cell growth and their angiogenesis ability in GC. However, most antiangiogenic agents have reported no benefit to overall survival (OS) compared to chemotherapy alone in local or advanced GC. In phase III clinical trials, only ramucirumab (anti-VEGFR blocker) and apatinib (VEGFR-TKI blocker) have reported an improved median overall response rate and prolonged OS and progression-free survival outcomes as a 2nd-line agent combined with chemotherapy treatment in advanced GC. By providing insights into the molecular mechanisms of angiogenesis associated with tumor progression in GC, this review will hopefully aid the optimization of antiangiogenesis strategies for GC therapy in combination with chemotherapy and adjuvant treatment.

Berberine hydrochloride counteracts enhanced IL-8 expression induced by SN 38 in AGS cells

IL-8 over-expression could enhance cancer metastasis. In present study, berberine hydrochloride (BER) triggered proliferative inhibition and G2/M arrest in AGS cells, down-regulated protein expression of cyclin B1, Bcl-2, up-regulated expression of p21, p53 and cleaved caspase 3, but showed no effect on protein expression of CHOP, Bip, and caspase 4. BER could down-regulate the enhanced IL-8 expression through down-regulating ERK1/2 and p38 MAPK over-activation induced by SN 38. The increased IL-8 mediated adhesive ability of AGS cells to HUVECs induced by SN 38, could be reduced by BER. Thus, BER could reduce the side-effect of SN 38 in clinic.

SN38 increases IL-8 expression through the MAPK pathways in HCT8 cells

The overexpression of interleukin-8 (IL-8) is closely associated with poor tumor differentiation, metastasis and tumor progression. This study aimed to examine the effects and mechanisms of action of SN38 (a metabolite of the camptothecin derivative, CPT-11) on IL-8 expression in HCT8 cells, using ELISA, CCK-8 and western blot analysis. Among jatrorrhizine, evodiamine, 5-fluorouracil and SN38, SN38 was found to inhibit the proliferation of HCT8 cells in a dose-dependent manner, but to increase IL-8 secretion from HCT8 cells. Of the other agents, evodiamine was found to inhibit both IL-8 secretion and cell proliferation, and jatrorrhizine was found to increase IL-8 secretion without any obvious inhibitory effect on cell proliferation. Further experiments revealed that the increased activation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK)1/2 and c-Jun N-terminal kinase (JNK) by SN38 contributed to the decreased cell proliferation and to the overexpression of IL-8 induced by SN38. Our results suggested that the MAPK pathways are activated by SN38, resulting in the upregulation of IL-8 expression and in the inhibition of cell proliferation in an IL-8-independent manner. Thus, the potential benefit of the use of a combination of camptothecin-11 with other chemical drugs with inhibitory effects on IL-8 expression, should be paid more attention in treating colon cancer.

MAPK pathways are involved in the inhibitory effect of berberine hydrochloride on gastric cancer MGC 803 cell proliferation and IL-8 secretion in vitro and in vivo

Gastric cancer is the second leading cause of cancer-associated mortality worldwide. This investigation aimed to identify whether the mitogen‑activated protein kinase (MAPK) signaling pathways are involved in the inhibitory effect of berberine hydrochloride (BER) on MGC 803 cells in vitro and in vivo. BER time‑ and dose‑dependently inhibited proliferation of MGC 803 cells. It also suppressed tumorigenesis in nude mice xenografted with MGC 803 cells. Additionally, BER reduced interleukin‑8 (IL‑8) secretion in vitro and in vivo. Further investigation demonstrated that inactivation of p38 MAPK, extracellular-signal regulated kinase 1/2 and c‑Jun N‑terminal kinase by BER contributed to the decreased proliferation and tumorigenesis, and the change in IL‑8 expression levels. However, there was no significant synergistic inhibitory effect of combined BER and evodiamine (EVO) treatment on tumorigenesis, and BER reduced the upregulation of IL‑8 induced by EVO in vivo. The results of the current study suggested that BER may be an effective and safe drug candidate for treating gastric cancer via modulation of the MAPK signaling pathways.

Gefitinib Synergizes with Irinotecan to Suppress Hepatocellular Carcinoma via Antagonizing Rad51-Mediated DNA-Repair

Chemotherapy is the only choice for most of the advanced hepatocellular carcinoma (HCC) patients, while few agents were available, making it an urgent need to develop new chemotherapy strategies. A phase II clinical trial suggested that the efficacy of irinotecan in HCC was limited due to dose-dependent toxicities. Here, we found that gefitinib exhibited synergistic activity in combination with SN-38, an active metabolite of irinotecan, in HCC cell lines. And the enhanced apoptosis induced by gefitinib plus SN-38 was a result from caspase pathway activation. Mechanistically, gefitinib dramatically promoted the ubiquitin–proteasome-dependent degradation of Rad51 protein, suppressed the DNA repair, gave rise to more DNA damages, and ultimately resulted in the synergism of these two agents. In addition, the increased antitumor efficacy of gefitinib combined with irinotecan was further validated in a HepG2 xenograft mice model. Taken together, our data demonstrated for the first time that the combination of irinotecan and gefitinib showed potential benefit in HCC, which suggests that Rad51 is a promising target and provides a rationale for clinical trials investigating the efficacy of the combination of topoisomerase I inhibitors and gefitinib in HCC.

Acquisition of doxorubicin resistance facilitates migrating and invasive potentials of gastric cancer MKN45 cells through up-regulating aldo-keto reductase 1B10

Continuous exposure to doxorubicin (DOX) accelerates hyposensitivity to the drug-elicited lethality of gastric cells, with increased risks of the recurrence and serious cardiovascular side effects. However, the detailed mechanisms underlying the reduction of DOX sensitivity remain unclear. In this study, we generated a DOX-resistant variant upon continuously treating human gastric cancer MKN45 cells with incremental concentrations of the drug, and investigated whether the gain of DOX resistance influences gene expression of four aldo-keto reductases (AKRs: 1B10, 1C1, 1C2 and 1C3). RT-PCR analysis revealed that among the enzymes AKR1B10 is most highly up-regulated during the chemoresistance induction. The up-regulation of AKR1B10 was confirmed by analyses of Western blotting and enzyme activity. The DOX sensitivity of MKN45 cells was reduced and elevated by overexpression and inhibition of AKR1B10, respectively. Compared to the parental MKN45 cells, the DOX-resistant cells had higher migrating and invasive abilities, which were significantly suppressed by addition of AKR1B10 inhibitors. Zymographic and real-time PCR analyses also revealed significant increases in secretion and expression of matrix metalloproteinase (MMP) 2 associated with DOX resistance. Moreover, the overexpression of AKR1B10 in the parental cells remarkably facilitated malignant progression (elevation of migrating and invasive potentials) and MMP2 secretion, which were lowered by the AKR1B10 inhibitors. These results suggest that AKR1B10 is a DOX-resistance gene in the gastric cancer cells, and is responsible for elevating the migrating and invasive potentials of the cells through induction of MMP2.

Y-box binding protein 1 enhances DNA topoisomerase 1 activity and sensitivity to camptothecin via direct interaction

Background

The Y-box binding protein 1 (YB-1) possesses pleiotropic functions through its interactions with various cellular proteins, and its high expression levels make it a potential useful prognostic biomarker for cancer cells. Eukaryotic DNA topoisomerases, such as DNA topoisomerase 1 (TOPO1) and DNA topoisomerase 2 (TOPO2), are the essential DNA metabolism regulators that usually overexpressed in cancer cells, and multiple proteins have been reported to regulate the enzyme activity and the clinical efficacy of their inhibitors. The present study unraveled the interaction of YB-1 with TOPO1, and further investigated the related function and potential mechanisms during the interaction.

Methods

The direct association of TOPO1 with specific domain of YB-1 was explored by co-immunoprecipitation and GST pull-down assays. The interaction function was further clarified by DNA relaxation assays, co-immunoprecipitation and WST-8 assays with in vitro gain- and loss- of function models.

Results

We found that YB-1 interacts directly with TOPO1 (but not with TOPO2) and promotes TOPO1 catalytic activity. Interactions between YB-1 and TOPO1 increased when cancer cells were treated with the TOPO1 inhibitor, camptothecin (CPT), but not with the TOPO2 inhibitor, adriamycin (ADM). Furthermore, we found that the interaction is prevented by pretreatment with the antioxidant agent, N-acetyl cysteine, and that YB-1 downregulation renders cells resistant to CPT.

Conclusions

Our findings suggest that nuclear YB-1 serves as an intracellular promoter of TOPO1 catalytic activity that enhances CPT sensitivity through its direct interaction with TOPO1.

Berberine hydrochloride IL-8 dependently inhibits invasion and IL-8-independently promotes cell apoptosis in MDA-MB-231 cells

Breast cancer, the leading cause of cancer-related mortality worldwide in females, has high metastastic and recurrence rates. The aim of the present study was to evaluate the anti-metastatic and anticancer in situ effect of berberine hydrochloride (BER) in MDA-MB-231 cells. BER dose-dependently inhibited proliferation and the IL-8 secretion of MDA-MB-231 cells. Additional experiments revealed that the inactivation of PI3K, JAK2, NF-κB and AP-1 by BER contributed to the decreased IL-8 secretion. BER abrogated cell invasion induced by IL-8 accompanied with the downregulation of the gene expression of MMP-2, EGF, E-cadherin, bFGF and fibronectin. In addition, BER reduced cell motility but induced G2/M arrest and cell apoptosis in an IL-8‑independent manner. BER modulated multiple signaling pathway molecules involved in the regulation of cell apoptosis, including activation of p38 MAPK and JNK and deactivation of JAK2, p85 PI3K, Akt and NF-κB. The enhanced cell apoptosis induced by BER was eliminated by inhibitors of p38 MAPK and JNK but was strengthened by activator of p38 MAPK. Thus, BER inhibited cell metastasis partly through the IL-8 mediated pathway while it induced G2/M arrest and promoted cell apoptosis through the IL-8 independent pathway. Apoptosis induced by BER was mediated by crosstalks of various pathways including activation of p38 MAPK and JNK pathways and inactivation of Jak2/PI3K/NF-κB/AP-1 pathways. The results suggested that BER may be an efficient and safe drug candidate for treating highly metastatic breast cancer.

Chemical principles for the design of a novel fluorescent probe with high cancer-targeting selectivity and sensitivity

Understanding of principles governing selective and sensitive cancer targeting is critical for development of chemicals for cancer diagnostics and treatment. We determined the underlying mechanisms of how a novel fluorescent small organic molecule, 3,6-bis(1-methyl-4-vinylpyridinium)carbazole diiodide (BMVC), selectively labels cancer cells but not normal cells. We show that BMVC is retained in the lysosomes of normal cells. In cancer cells, BMVC escapes lysosomal retention and localizes to the mitochondria or to the nucleus, where DNA-binding dramatically increases BMVC fluorescence intensity, allowing it to light up only cancer cells. Structure-function analyses of BMVC derivatives show that hydrogen-bonding capacity is a key determinant of lysosomal retention in normal cells, whereas lipophilicity directs these derivatives to the mitochondria or the nucleus in cancer cells. In addition, drug-resistant cancer cells preferentially retain BMVC in their lysosomes compared to drug-sensitive cancer cells, and BMVC can be released from drug-resistant lysosomes using lysosomotropic agents. Our results further our understanding of how properties of cellular organelles differ between normal and cancer cells, which can be exploited for diagnostic and/or therapeutic use. We also provide physiochemical design principles for selective targeting of small molecules to different organelles. Moreover, our results suggest that agents which can increase lysosomal membrane permeability may re-sensitize drug-resistant cancer cells to chemotherapeutic agents.

Helicobacter pylori and interleukin-8 in gastric cancer

Helicobacter pylori (H. pylori) is a major etiological factor in the development of gastric cancer. Large-scale epidemiological studies have confirmed the strong association between H. pylori infection and both cancer development and progression. Interleukin-8 (IL-8) is overexpressed in gastric mucosa exposed to H. pylori. The expression of IL-8 directly correlates with a poor prognosis in gastric cancer. IL-8 is multifunctional. In addition to its potent chemotactic activity, it can induce proliferation and migration of cancer cells. In this review, we focus on recent insights into the mechanisms of IL-8 signaling associated with gastric cancer. The relationship between IL-8 and H. pylori is discussed. We also summarize the current therapeutics against IL-8 in gastric cancer.

Treatment with gefitinib or lapatinib induces drug resistance through downregulation of topoisomerase IIα expression

The EGF receptor (EGFR) is therapeutically targeted by antibodies and small molecules in solid tumors including lung, colorectal, and breast cancer. However, chemotherapy remains important, and efforts to improve efficacy through combination with targeted agents is challenging. This study examined the effects of short and long durations of exposure to the EGFR- and HER2-targeted tyrosine kinase inhibitors (TKI) gefitinib and lapatinib, on induction of cell death and DNA damage by topoisomerase IIα (Topo IIα) poisons, in the SK-Br-3 HER2-amplified breast cancer cell line. Short exposure to either gefitinib or lapatinib for 1 hour did not affect the induction of apoptosis by the Topo IIα poisons doxorubicin, etoposide, and m-AMSA. In contrast, cells treated for 48 hours were resistant to all three drugs. Short exposure (1 hour) to TKI did not alter the number of DNA single- or double-strand breaks (DSB) induced, whereas longer exposure (48 hours) reduced the number of DNA DSBs and the formation of γ-H2AX foci. Both gefitinib and lapatinib reduced the expression and activity of Topo IIα at 48 hours. Studies using a cell line with inducible downregulation of Topo IIα showed that expression of Topo IIα, and not Topo IIβ, determined the number of DNA strand breaks induced by these chemotherapeutic agents. These results indicate that prolonged exposure to TKIs targeting EGFR and HER2 induce resistance to doxorubicin, etoposide, and m-AMSA through downregulation of Topo IIα. This may explain why their addition to chemotherapy regimens have not increased efficacy.

Berberine counteracts enhanced IL-8 expression of AGS cells induced by evodiamine

AIMS

Although showing an anti-tumor activity, evodiamine also up-regulated IL-8 production of human gastric cancer AGS cells. This study aimed to assess this effect and to examine whether co-administration with berberine counteracts it.

MAIN METHODS

MTT assay was used to assess the cell proliferation and adhesive ability. Flow cytometry was performed to measure the cell cycle distribution. Wound healing assay was used to detect the migration ability of cells. IL-8 production was determined by ELISA. Levels of mRNA expression of IL-8, VCAM-1 and ICAM-1 were measured by real-time PCR. Molecular pathways involved were evaluated by ELISA and western-blotting methods.

KEY FINDINGS

Evodiamine triggered proliferative inhibition and cell cycle arrest, and decreased migration of AGS cells. IL-8 expression and the adhesive ability of AGS cells to HUVECs were significantly increased by evodiamine, but were inhibited after being co-treated with berberine in AGS cells. As IL-8 was neutralized, increased adhesion of AGS cells to HUVECs induced by evodiamine was abolished. Berberine significantly suppressed the up-regulation of VCAM-1 and the down-regulation of ICAM-1 induced by evodiamine. Evodiamine provoked IL-8 secretion via ERK1/2, SAPK/JNK, JAK2 and AP-1 pathways which could be counteracted by berberine.

SIGNIFICANCE

Although showing anti-proliferative and anti-migratory activities in AGS cells, evodiamine displayed a potential tendency to promote metastasis of gastric cancer cells by increasing IL-8 secretion and adhesion molecules. However, berberine could counteract the side-effect and simultaneously keep anti-proliferative and anti-migratory properties of evodiamine on AGS cells, which reduces the risk to use evodiamine in therapy of gastric cancers.

Association among polymorphisms in EGFR gene exons, lifestyle and risk of gastric cancer with gender differences in Chinese Han subjects

Background

The epidermal growth factor receptor (EGFR) gene plays a key role in tumor survival, invasion, angiogenesis, and metastatic spread. Recent studies showed that gastric cancer (GC) was associated with polymorphisms of the EGFR gene and environmental influences, such as lifestyle factors. In this study, seven known SNPs in EGFR exons were investigated in a high-risk Chinese population in Jiangsu province to test whether genetic variants of EGFR exons and lifestyle are associated with an increased risk of GC.

Methodology/Principal Findings

A hospital-based case-control study was performed in Jiangsu province. The results showed that smoking, drinking and preference for salty food were significantly associated with the risk of GC. The differences of lifestyle between males and females might be as the reason of higher incidence rates in males than those in females. Seven exon SNPs were genotyped rs2227983,rs2072454,rs17337023,rs1050171,rs1140475, rs2293347, and rs28384375. It was noted that the variant rs2072454 T allele and TT genotype were significantly associated with an increased risk of GC. Interestingly, our result suggested the ACAGCA haplotype might be associated with decreased risk of GC. However, no significant association was examined between the other six SNPs and the risk of GC both in the total population and the age-matching population even with gender differences.

Conclusions

Smoking, drinking and preference for salty food were significantly associated with the risk of GC in Jiangsu province with gender differences. Although only one SNP (rs2072454) was significantly associated with an increased risk of GC, combined the six EGFR exon SNPs together may be useful for predicting the risk of GC.

PDGF α receptor is a mediator for Cisplatin-induced Met expression

For decades, platinum drugs have been the mainstay of cancer treatment. However, over time, drug resistance develops, leaving few treatment options. Here we show that platelet-derived growth factor α receptor (PDGF α receptor)-mediated signaling plays a key role in hepatocyte growth factor (HGF) receptor (c-Met) upregulation, which in turn is thought to play an important role in chemotherapy resistance. PDGF α receptor inhibition eliminates cisplatin-dependent Met expression in cervical cancer cell lines. PDGF α receptor inhibitors are widely used in clinical settings, suggesting that the clinical translation of our findings could reduce the suffering of people from drug resistance.

Erlotinib increases sensitivity of MKN45 cells to radiotherapy

AIM: To observe the effect of erlotinib combined with radiotherapy on cell cycle progression and apoptosis of human gastric carcinoma MKN45 cells to explore the mechanism by which erlotinib increases the sensitivity of MKN45 cells to radiotherapy.

METHODS: The effect of erlotinib and radiotherapy on MKN45 cells was examined by MTT assay and colony formation assay. The median inhibitory concentration (IC₅₀) and radiobiological parameters D₀ and Dq were calculated. Cell apoptosis and cell cycle progression were examined by flow cytometry. The expression of Bcl-2 and Bax proteins was detected by Western blot.

RESULTS: Both erlotinib and radiotherapy could inhibit MKN45 cell growth in a concentration- and dose-dependent manner (both P < 0.01). The inhibitory effect of erlotinib combined with radiotherapy on MKN45 cell growth was better than that of erlotinib or radiation alone. Combination treatment significantly decreased the percentages of cells in S phase cells and increased those in G₂/M and G₀/G₁ phases (71.87 ± 0.77 vs 60.72 ± 0.26, P < 0.01) and cell apoptosis. After treatment with erlotinib combined with radiotherapy, Bcl-2 protein expression decreased and Bax protein expression increased.

CONCLUSION: Erlotinib increases radiosensitivity of MKN45 cells by increasing the percentages of cells in G₂/M and G₀/G₁ phases and decreasing Bcl-2/Bax ratio to induce apoptosis.

Targeted therapies for gastric cancer: current status

Gastric cancer represents one of the most common cancers internationally. Unfortunately the majority of patients still present at an advanced stage, and despite advances in diagnostic and treatment strategies, outcomes still remain poor with high mortality rates despite a decline in incidence. Whilst the utility of classical chemotherapy agents has been explored thoroughly (and continues to be investigated, alone or in various combinations), advances have been slow and the efficacy of these agents has reached a plateau. As such, the focus of recent study has shifted toward developing a greater understanding of the molecular biology of carcinogenesis and the cancer cell phenotype, and, in turn, the development of rationally designed drugs that target molecular aberrancies in signal transduction pathways specific to gastric cancer. These targets include circulating growth and angiogenic factors, cell surface receptors, and other molecules that comprise downstream intracellular signalling pathways, including receptor tyrosine kinases. Therapeutic advances in this area significantly lag behind other solid organ malignancies such as breast and colorectal cancer. This article reviews the role of targeted therapies in gastric cancer, including rationale and mechanism of action, current and emerging data, as single-agent therapy or in combination regimens. A recently published randomized phaseIII trial supporting the use of trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2)/neu monoclonal antibody, in a selected population of patients is discussed. Therapies that have been evaluated in phase II trials are also reviewed, as well as promising new therapies currently being investigated in preclinical or phase I studies. There is optimism that targeted therapies, whether as single-agent therapy or in combination with traditional therapies, including chemotherapy, radiotherapy and surgery, may yet have an impact on improvement of the overall prognosis of gastric cancer.

Breast cancer expressing the activated HER2/neu is sensitive to gefitinib in vitro and in vivo and acquires resistance through a novel point mutation in the HER2/neu

The HER2/neu oncogene is an important diagnostic and prognostic factor and therapeutic target in breast and other cancers. We developed and characterized a breast cancer cell line (Bam1a) that overexpresses the activated HER2/neu and ErbB-3 and has a gene expression profile consistent with the ErbB-2 genetic signature. We evaluated the effects of the epidermal growth factor receptor (EGFR)/HER2 inhibitor, gefitinib, on this breast tumor line in vitro and in vivo. We characterized the effects of gefitinib on EGFR, HER2, and ErbB-3 phosphorylation by Western blot and determined the effects on downstream signaling through growth, survival, and stress pathways and the effect on proliferation, cell cycle, and apoptosis. Gefitinib treatment diminished phosphorylation of the ErbB-3 > EGFR > HER2/neu and signal transducers and activators of transcriptions in a dose-dependent fashion. Downstream mitogenic signaling through mitogen-activated protein (MAP)/extracellular signal regulated kinase kinase, p44/42 MAP kinase (MAPK) and stress signaling through c-Jun-NH(2)-kinase (JNK) 1 and c-Jun was impaired (1 micromol/L, 4-24 h), leading to cytostasis and cell cycle arrest within 24 h by decreased cyclin D1, cyclin B1, and p(Ser795)Rb and increased p27. Proliferation and colony formation were inhibited at 0.5 and 1 micromol/L, respectively, and correlated with altered gene expression profiles. Diminished survival signaling through Akt, induction of bim, loss of connexin43, and decreased production of vascular endothelial growth factor-D preceded caspase-3 and poly(ADP)ribose polymerase (PARP) cleavage and apoptosis (>50% 2 micromol/L, 48 h). Oral administration of gefitinib was able to prevent the outgrowth of Bam1a tumor cells from palpable lesions, shrink established tumors, eliminate HER2 and HER3 phosphorylation, and decrease MAPK and Akt signaling in vivo. A variant of the Bam1a cell line, IR-5, with acquired ability to grow in 5 micromol/L gefitinib was developed and characterized. IR-5 bears a novel point mutation in the HER2/neu that corresponds to a L726I in the ATP-binding pocket and correlates with a log decrease in sensitivity to gefitinib, increased heterodimerization with EGFR and HER3, and impaired down-regulation. Gene expression profiling of IR-5 showed increased expression of EMP-1, NOTCH-1, FLT-1, PDGFB, and several other genes that may contribute to the resistant phenotype and sustain signaling through MAPK and Akt. This model will be useful in understanding the differences between intrinsic drug sensitivity and acquired resistance in the context of therapeutic strategies that target oncogene addicted diseases.