Gefitinib induces apoptosis in human glioma cells by targeting Bad phosphorylation

Application of EGFR-TKIs in brain tumors, a breakthrough in future?

Brain tumors, both primary and secondary, represent a significant clinical challenge due to their high mortality and limited treatment options. Primary brain tumors, such as gliomas and meningiomas, and brain metastases from cancers such as non-small cell lung cancer and breast cancer require innovative therapeutic strategies. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR -TKIs) have emerged as a promising treatment option, particularly for tumors harboring EGFR mutations. This review examines the use of EGFR-TKIs in brain tumors, highlighting both laboratory and clinical research findings. In primary brain tumors and brain metastases, EGFR-TKIs have shown potential in controlling tumor growth and improving patient outcomes. Advanced applications, such as nano-formulated EGFR-TKIs and combination therapies with other pathway inhibitors, are being investigated to improve efficacy and overcome resistance. Challenges such as treatment-related events, resistance mechanisms and blood-brain barrier penetration remain significant hurdles. Addressing tumor heterogeneity through personalized medicine approaches is critical to optimizing EGFR-TKI therapies. This review highlights the need for continued research to refine these therapies and improve survival for patients with brain tumors.

Cinnamaldehyde impacts key cellular signaling pathways for induction of programmed cell death in high-grade and low-grade human glioma cells

OBJECTIVE

Primary tumors of the brain and a large percent of malignant brain tumors are gliomas. Gliomas comprise high-grade gliomas like glioblastoma multiforme (GBMs), many of which have mutation in the tumor suppressor p53 gene and low-grade gliomas (LGGs). LGGs can progress to GBMs due to various factors. The available treatment options for GBMs and LGGs include surgical resection, radiation and chemotherapy. The chemotherapeutic drug available in the clinic is temozolomide (TMZ). However, TMZ can cause damage to DNA if taken for prolonged period. This warrants the discovery of drugs that would potentially elicit less adverse side effects while maintaining anticancer activity. To this end, we evaluated the impact of cinnamaldehyde (CA), a single, purified component of the natural product cinnamon.

RESULTS

The elucidation of the mechanism of action revealed the impact of CA on reactive oxygen species (ROS) levels. Moreover, its effect on the extrinsic programmed cell death pathway resulted in the increase of apoptotic cell populations, invoking multicaspase. Notably, the cell survival/death pivotal molecule Bcl-2 was impacted. These effects were observed in both the types of brain tumor cells studied: GBMs, represented by U251 cells (p53 mutated cell line) and LGGs represented by H4 cells. Results from the current study suggest potential for CA as a therapeutic option as it is expected to have fewer adverse side effects due to it being a component of a natural product and possibly deter the progression of LGGs to GBMs.

18β-glycyrrhetinic acid regulates mitochondrial ribosomal protein L35-associated apoptosis signaling pathways to inhibit proliferation of gastric carcinoma cells

BACKGROUND

Gastric carcinoma (GC) is a common gastrointestinal malignancy worldwide. Based on the cancer-related mortality, the current prevention and treatment strategies for GC still show poor clinical results. Therefore, it is important to find effective drug treatment targets.

AIM

To explore the mechanism by which 18β-glycyrrhetinic acid (18β-GRA) regulates mitochondrial ribosomal protein L35 (MRPL35) related signal proteins to inhibit the proliferation of GC cells.

METHODS

Cell counting kit-8 assay was used to detect the effects of 18β-GRA on the survival rate of human normal gastric mucosal cell line GES-1 and the proliferation of GC cell lines MGC80-3 and BGC-823. The apoptosis and cell cycle were assessed by flow cytometry. Cell invasion and migration were evaluated by Transwell assay, and cell scratch test was used to detect cell migration. Furthermore, a tumor model was established by hypodermic injection of 2.5 × 10⁶ BGC-823 cells at the selected positions of BALB/c nude mice to determine the effect of 18β-GRA on GC cell proliferation, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to detect MRPL35 expression in the engrafted tumors in mice. We used the term tandem mass tag (TMT) labeling combined with liquid chromatography–tandem mass spectrometry to screen for differentially expressed proteins (DEPs) extracted from GC cells and control cells after 18β-GRA intervention. A detailed bioinformatics analysis of these DEPs was performed, including Gene Ontology annotation and enrichment analysis, Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, and so on. Moreover, STRING database (https://string-db.org/) was used to predict protein-protein interaction (PPI) relationships and Western blot was used to detect the expression of proteins of interest in GC cells.

RESULTS

The results indicated that 18β-GRA could inhibit the proliferation of GC cells in a dose- and time-dependent manner. It could induce GC cell apoptosis and arrest the cell cycle at G0/G1 phase. The proportion of cells arrested at S phase decreased with the increase of 18-GRA dose, and the migration and invasiveness of GC cells were inhibited. The results of animal experiments showed that 18β-GRA could inhibit tumor formation in BALB/c nude mice, and qRT-PCR results showed that MRPL35 expression level was significantly reduced in the engrafted tumors in mice. Using TMT technology, 609 DEPs, among which 335 were up-regulated and 274 were down-regulated, were identified in 18β-GRA intervention compared with control. We found that the intervention of 18β-GRA in GC cells involved many important biological processes and signaling pathways, such as cellular processes, biological regulation, and TP53 signaling pathway. Notably, after the drug intervention, MRPL35 expression was significantly down-regulated (P = 0.000247), TP53 expression was up-regulated (P = 0.02676), and BCL2L1 was down-regulated (P = 0.01699). Combined with the Retrieval of Interacting Genes/Proteins database, we analyzed the relationship between MRPL35, TP53, and BCL2L1 signaling proteins, and we found that COPS5, BAX, and BAD proteins can form a PPI network with MRPL35, TP53, and BCL2L1. Western blot analysis confirmed the intervention effect of 18β-GRA on GC cells, MRPL35, TP53, and BCL2L1 showed dose-dependent up/down-regulation, and the expression of COPS5, BAX, and BAD also increased/decreased with the change of 18β-GRA concentration.

CONCLUSION

18β-GRA can inhibit the proliferation of GC cells by regulating MRPL35, COPS5, TP53, BCL2L1, BAX, and BAD.

Crystal structure of human 14-3-3ζ complexed with the noncanonical phosphopeptide from proapoptotic BAD

Several signaling pathways control phosphorylation of the proapoptotic protein BAD and its phosphorylation-dependent association with 14-3-3 proteins in the cytoplasm. The stability of the 14-3-3/BAD complex determines the cell fate: unphosphorylated BAD escapes from 14-3-3, migrates to the mitochondria and initiates apoptosis. While the 14-3-3/BAD interaction represents a promising drug target, it lacks structural characterization. Among several phosphosites identified in vivo, Ser75 and Ser99 of human BAD match the consensus sequence RXXpSXP recognized by 14-3-3 and, therefore, represent canonical 14-3-3-binding sites. Yet, BAD contains other serines phosphorylatable in vivo, whose role is less understood. Here, we report a 2.36 Å crystal structure of 14-3-3ζ complexed with a BAD fragment which includes residues Ser74 and Ser75, both being substrates for protein kinases. While the BAD peptide is anchored to 14-3-3 by phosphoserine as expected, the BAD peptide was unexpectedly phosphorylated at Ser74 instead of Ser75, revealing noncanonical binding within the amphipathic groove and leading to a one-step positional shift and reorganization of the interface. This observation exemplifies plasticity of the amphipathic 14-3-3 groove in accommodating various peptides and suggests the redundancy of Ser74 and Ser75 phosphosites with respect to binding of BAD to 14-3-3.

Regulation of autophagy as a therapeutic option in glioblastoma

Around three out of one hundred thousand people are diagnosed with glioblastoma multiforme, simply called glioblastoma, which is the most common primary brain tumor in adults. With a dismal prognosis of a little over a year, receiving a glioblastoma diagnosis is oftentimes fatal. A major advancement in its treatment was made almost two decades ago when the alkylating chemotherapeutic agent temozolomide (TMZ) was combined with radiotherapy (RT). Little progress has been made since then. Therapies that focus on the modulation of autophagy, a key process that regulates cellular homeostasis, have been developed to curb the progression of glioblastoma. The dual role of autophagy (cell survival or cell death) in glioblastoma has led to the development of autophagy inhibitors and promoters that either work as monotherapies or as part of a combination therapy to induce cell death, cellular senescence, and counteract the ability of glioblastoma stem cells (GSCs) for initiating tumor recurrence. The myriad of cellular pathways that act upon the modulation of autophagy have created contention between two groups: those who use autophagy inhibition versus those who use promotion of autophagy to control glioblastoma growth. We discuss rationale for using current major therapeutics, their molecular mechanisms for modulation of autophagy in glioblastoma and GSCs, their potentials for making strides in combating glioblastoma progression, and their possible shortcomings. These shortcomings may fuel the innovation of novel delivery systems and therapies involving TMZ in conjunction with another agent to pave the way towards a new gold standard of glioblastoma treatment.

Endoplasmic Reticulum Stress Contributes to Gefitinib-Induced Apoptosis in Glioma

Adequate stress on the Endoplasmic Reticulum (ER) with the Unfolded Protein Response (UPR) could maintain glioma malignancy. Uncontrolled ER stress, on the other hand, predisposes an apoptosis-dominant UPR program. We studied here the proapoptotic actions of the Epidermal Growth Factor Receptor (EGFR) inhibitor gefitinib, with the focus on ER stress. The study models were human H4 and U87 glioma cell lines. We found that the glioma cell-killing effects of gefitinib involved caspase 3 apoptotic cascades. Three branches of ER stress, namely Activating Transcription Factor-6 (ATF6), Protein Kinase R (PKR)-Like ER Kinase (PERK), and Inositol-Requiring Enzyme 1 (IRE1), were activated by gefitinib, along with the elevation of intracellular free Ca2+, Reactive Oxygen Species (ROS), and NADPH Oxidase2/4 (NOX2/4). Specifically, elevated IRE1 phosphorylation, Tumor Necrosis Factor (TNF) Receptor-Associated Factor-2 (TRAF2) expression, Apoptosis Signal-Regulating Kinase-1 (Ask1) phosphorylation, c-Jun N-Terminal Kinase (JNK) phosphorylation, and Noxa expression appeared in gefitinib-treated glioma cells. Genetic, pharmacological, and biochemical studies further indicated an active ROS/ER stress/Ask1/JNK/Noxa axis causing the glioma apoptosis induced by gefitinib. The findings suggest that ER-stress-based therapeutic targeting could be a promising option in EGFR inhibitor glioma therapy, and may ultimately achieve a better patient response.

Autophagy as a Potential Therapy for Malignant Glioma

Glioma is the most frequent and aggressive type of brain neoplasm, being anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM), its most malignant forms. The survival rate in patients with these neoplasms is 15 months after diagnosis, despite a diversity of treatments, including surgery, radiation, chemotherapy, and immunotherapy. The resistance of GBM to various therapies is due to a highly mutated genome; these genetic changes induce a de-regulation of several signaling pathways and result in higher cell proliferation rates, angiogenesis, invasion, and a marked resistance to apoptosis; this latter trait is a hallmark of highly invasive tumor cells, such as glioma cells. Due to a defective apoptosis in gliomas, induced autophagic death can be an alternative to remove tumor cells. Paradoxically, however, autophagy in cancer can promote either a cell death or survival. Modulating the autophagic pathway as a death mechanism for cancer cells has prompted the use of both inhibitors and autophagy inducers. The autophagic process, either as a cancer suppressing or inducing mechanism in high-grade gliomas is discussed in this review, along with therapeutic approaches to inhibit or induce autophagy in pre-clinical and clinical studies, aiming to increase the efficiency of conventional treatments to remove glioma neoplastic cells.

Design, expression, purification and crystallization of human 14-3-3ζ protein chimera with phosphopeptide from proapoptotic protein BAD

14-3-3 protein isoforms regulate multiple processes in eukaryotes, including apoptosis and cell division. 14-3-3 proteins preferentially recognize phosphorylated unstructured motifs, justifying the protein-peptide binding approach to study 14-3-3/phosphotarget complexes. Tethering of human 14-3-3σ with partner phosphopeptides via a short linker has provided structural information equivalent to the use of synthetic phosphopeptides, simultaneously facilitating purification and crystallization. Nevertheless, the broader applicability to other 14-3-3 isoforms and phosphopeptides was unclear. Here, we designed a novel 14-3-3ζ chimera with a conserved phosphopeptide from BAD, whose complex with 14-3-3 is a gatekeeper of apoptosis regulation. The chimera could be bacterially expressed and purified without affinity tags. Co-expressed PKA efficiently phosphorylates BAD within the chimera and blocks its interaction with a known 14-3-3 phosphotarget, suggesting occupation of the 14-3-3 grooves by the tethered BAD phosphopeptide. Efficient crystallization of the engineered protein suggests suitability of the "chimeric" approach for studies of other relevant 14-3-3 complexes.

Synergistic Action of Gefitinib and GSK41364A Simultaneously Loaded in Ratiometrically-Engineered Polymeric Nanoparticles for Glioblastoma Multiforme

Glioblastoma Multiforme is a deadly cancer of glial cells with very low survival rates. Current treatment options are invasive and have serious side effects. Single drug treatments make the tumor refractory after a certain period. Combination therapies have shown improvements in treatment responses against aggressive forms of cancer and are becoming a mainstay in the management of cancer. The purpose of this study is to design a combinatorial treatment regimen by engineering desired ratios of two different small molecule drugs (gefitinib and GSK461364A) in a single carrier that can reduce off-target effects and increase their bioavailability. Synergistic effects were observed with our formulation when optimal ratios of gefitinib and GSK461364A were loaded in poly (lactic-co-glycolic) acid and polyethylene glycol (PLGA-PEG) nanoparticles and tested for efficacy in U87-malignant glioma (U87-MG) cells. Combination nanoparticles proved to be more effective compared to single drug encapsulated nanoparticles, free drug combinations, and the mixture of two single loaded nanoparticles, with statistically significant values at certain ratios and drug concentrations. We also observed drastically reduced clonogenic potential of the cells that were treated with free drugs and nanoparticle combinations in a colony forming assay. From our findings, we conclude that the combination of GSK461364A and higher concentrations of gefitinib when encapsulated in nanoparticles yield synergistic killing of glioma cells. This study could form the basis for designing new combination treatments using nanoparticles to deliver multiple drugs to cancer cells for synergistic effects.

Autophagic and Apoptotic Pathways as Targets for Chemotherapy in Glioblastoma

Glioblastoma multiforme is the most malignant and aggressive type of brain tumor, with a mean life expectancy of less than 15 months. This is due in part to the high resistance to apoptosis and moderate resistant to autophagic cell death in glioblastoma cells, and to the poor therapeutic response to conventional therapies. Autophagic cell death represents an alternative mechanism to overcome the resistance of glioblastoma to pro-apoptosis-related therapies. Nevertheless, apoptosis induction plays a major conceptual role in several experimental studies to develop novel therapies against brain tumors. In this review, we outline the different components of the apoptotic and autophagic pathways and explore the mechanisms of resistance to these cell death pathways in glioblastoma cells. Finally, we discuss drugs with clinical and preclinical use that interfere with the mechanisms of survival, proliferation, angiogenesis, migration, invasion, and cell death of malignant cells, favoring the induction of apoptosis and autophagy, or the inhibition of the latter leading to cell death, as well as their therapeutic potential in glioma, and examine new perspectives in this promising research field.

Cancer stem cell metabolism: a potential target for cancer therapy

Cancer Stem cells (CSCs) are a unipotent cell population present within the tumour cell mass. CSCs are known to be highly chemo-resistant, and in recent years, they have gained intense interest as key tumour initiating cells that may also play an integral role in tumour recurrence following chemotherapy. Cancer cells have the ability to alter their metabolism in order to fulfil bio-energetic and biosynthetic requirements. They are largely dependent on aerobic glycolysis for their energy production and also are associated with increased fatty acid synthesis and increased rates of glutamine utilisation. Emerging evidence has shown that therapeutic resistance to cancer treatment may arise due to dysregulation in glucose metabolism, fatty acid synthesis, and glutaminolysis. To propagate their lethal effects and maintain survival, tumour cells alter their metabolic requirements to ensure optimal nutrient use for their survival, evasion from host immune attack, and proliferation. It is now evident that cancer cells metabolise glutamine to grow rapidly because it provides the metabolic stimulus for required energy and precursors for synthesis of proteins, lipids, and nucleic acids. It can also regulate the activities of some of the signalling pathways that control the proliferation of cancer cells.

This review describes the key metabolic pathways required by CSCs to maintain a survival advantage and highlights how a combined approach of targeting cellular metabolism in conjunction with the use of chemotherapeutic drugs may provide a promising strategy to overcome therapeutic resistance and therefore aid in cancer therapy.

Gefitinib induces lung cancer cell autophagy and apoptosis via blockade of the PI3K/AKT/mTOR pathway

Gefitinib is a selective inhibitor of the tyrosine kinase epidermal growth factor receptor, which inhibits tumor pathogenesis, metastasis and angiogenesis, as well as promoting apoptosis. Therefore, gefitinib presents an effective drug for the targeted therapy of lung cancer. However, the underlying mechanisms by which gefitinib induces lung cancer cell death remain unclear. To investigate the effects of gefitinib on lung cancer cells and the mechanism of such, the present study analyzed the effect of gefitinib on the autophagy, apoptosis and proliferation of the A549 and A549-gefitinib-resistant (GR) cell lines GR. The regulation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) pathway was also investigated. Acridine orange staining revealed that gefitinib induced autophagy of A549 cells but not A549-GR cells. In addition, gefitinib promoted apoptosis and inhibited proliferation of A549 cells but not A549-GR cells. Furthermore, western blot analysis demonstrated that gefitinib treatment led to the downregulation of PI3K, AKT, pAKT, mTOR and phosphorylated-mTOR protein expression in A549 cells but not A549-GR cells. LY294002 blocked the PI3K/AKT/mTOR pathway and induced autophagy and apoptosis of A549 cells, however, no synergistic effect was observed following combined treatment with gefitinib and LY294002. In conclusion, the results of the present study indicate that gefitinib promotes autophagy and apoptosis of lung cancer cells via blockade of the PI3K/AKT/mTOR pathway, which leads to lung cancer cell death.

Epidermal growth factor receptor inhibitor cancer drug gefitinib modulates cell growth and differentiation of acute myeloid leukemia cells via histamine receptors

BACKGROUND

Epidermal growth factor receptor (EGFR) inhibitor gefitinib (Iressa) is used for treating non-small cell lung cancer. Gefitinib also induces differentiation in acute myeloid leukemia (AML) cell lines and patient samples lacking EGFR by an unknown mechanism. Here we dissected the mechanism of gefitinib action responsible for its EGFR-independent effects.

METHODS

Signaling events were analyzed by homogenous time-resolved fluorescence and immunoblotting. Cellular proliferation and differentiation were assessed by ATP measurement, trypan blue exclusion, 5-bromo-2'-deoxyuridine incorporation and flow-cytometry. Gefitinib and G protein-coupled receptor (GPCR) interactions were assessed by β-arrestin recruitment, luciferase and radioligand competition assays. Role of histamine receptors (HR) in gefitinib actions were assessed by HR knockdown or pharmacological modulation. EGFR and HR interaction was assessed by co-immunoprecipitation.

RESULTS

Gefitinib reduced cyclic AMP content in both AML and EGFR-expressing cells and induced ERK phosphorylation in AML cells. Dibutyryl-cAMP or PD98059 suppressed gefitinib-induced AML cell cytostasis and differentiation. Gefitinib bound to and modulated HRs with subtype selectivity. Pharmacological or genetic modulations of H2 and H4 HRs (H2R and H4R) not only suppressed gefitinib-induced cytostasis and differentiation of AML cells but also blocked EGFR and ERK1/2 inhibition in MDA-MB-231 cells. Moreover, in MDA-MB-231 cells gefitinib enhanced EGFR interaction with H4R that was blocked by H4R agonist 4-methyl histamine (4MH).

CONCLUSION

HRs play critical roles in anti-cancer effects of gefitinib in both EGFR-deficient and EGFR-rich environments.

GENERAL SIGNIFICANCE

We furnish fresh insights into gefitinib functions which may provide new molecular clues to its efficacy and safety issues.

Metabolic reprogramming in cancer cells: glycolysis, glutaminolysis, and Bcl-2 proteins as novel therapeutic targets for cancer

Nearly a century ago, Otto Warburg made the ground-breaking observation that cancer cells, unlike normal cells, prefer a seemingly inefficient mechanism of glucose metabolism: aerobic glycolysis, a phenomenon now referred to as the Warburg effect. The finding that rapidly proliferating cancer cells favors incomplete metabolism of glucose, producing large amounts of lactate as opposed to synthesizing ATP to sustain cell growth, has confounded scientists for years. Further investigation into the metabolic phenotype of cancer has expanded our understanding of this puzzling conundrum, and has opened new avenues for the development of anti-cancer therapies. Enhanced glycolytic flux is now known to allow for increased synthesis of intermediates for sustaining anabolic pathways critical for cancer cell growth. Alongside the increase in glycolysis, cancer cells transform their mitochondria into synthesis machines supported by augmented glutaminolysis, supplying lipid production, amino acid synthesis, and the pentose phosphate pathways. Inhibition of several of the key enzymes involved in these pathways has been demonstrated to effectively obstruct cancer cell growth and multiplication, sensitizing them to apoptosis. The modulation of various regulatory proteins involved in metabolic processes is central to cancerous reprogramming of metabolism. The finding that members of one of the major protein families involved in cell death regulation also aberrantly regulated in cancers, the Bcl-2 family of proteins, are also critical mediators of metabolic pathways, provides strong evidence for the importance of the metabolic shift to cancer cell survival. Targeting the anti-apoptotic members of the Bcl-2 family of proteins is proving to be a successful way to selectively target cancer cells and induce apoptosis. Further understanding of how cancer cells modify metabolic regulation to increase channeling of substrates into biosynthesis will allow for the discovery of novel drug targets to treat cancer. In the present review, we focused on the recent developments in therapeutic targeting of different steps in glycolysis, glutaminolysis and on the metabolic regulatory role of Bcl-2 family proteins.

Valproic acid sensitizes human glioma cells to gefitinib-induced autophagy

Autophagy and apoptosis represent important cellular processes involved in cancer cell killing mechanisms. Epidermal growth factor receptor inhibitor gefitinib and valproic acid have been implicated in the treatment of malignancies including glioma involving autophagic and apoptotic mechanisms. Therefore, it is interesting to investigate whether a combination of gefitinib and valproic acid shows better cancer cell killing effect on human glioma cells. We found that a nontoxic concentration of valproic acid sensitized U87 and T98G glioma cells to gefitinib cytotoxicity by inhibiting cell growth and long-term clonogenic survival. The augmented consequences were accompanied by the formation of autophagic vacuoles, conversion of microtubule-associated protein-1 light chain 3-II (LC3-II), and degradation of p62. Autophagy inhibitor 3-methyladenosine and chloroquine and genetic silencing of LC3 but not broad-spectrum caspase inhibitor attenuated gefitinib/valproic acid-induced growth inhibition. Gefitinib/valproic acid-induced autophagy was accompanied by the activation of liver kinase-B1 (LKB1)/AMP-activated protein kinase (AMPK)/ULK1. Silencing of AMPK and ULK1 suppressed gefitinib/valproic acid-induced autophagy and growth inhibition. Mechanistic studies showed that gefitinib/valproic acid increased intracellular reactive oxygen species generation and N-acetyl cysteine attenuated gefitinib/valproic acid-caused autophagy and growth inhibition. In addition to demonstrating the autophagic mechanisms of gefitinib/valproic acid, the results of this study further suggest that intracellular oxidative stress and the LKB1/AMPK signaling might be a potential target for the development of therapeutic strategy against glioma.

[Association between GNAS1 T393C polymorphism and therapeutic efficacy of tyrosine kinase inhibitor in pretreated advanced non-small cell lung cancer with unknown EGFR mutation status]

BACKGROUND AND OBJECTIVE

Epidermal growth factor receptor (EGFR)-activating mutation predicts excellent response to EGFR tyrosine kinase inhibitors (TKIs). However, lung cancer patients are often with unknown EGFR mutation status because there are little tumor specimen to determine. TKIs induce tumor cell apoptosis which associates with several apoptosis-related genes. To explore the association between GNAS1 T393C polymorphism and therapeutic efficacy of TKI in pretreated advanced non-small cell lung cancer (NCSLC) with unknown EGFR mutation status.

METHODS

A total of 116 patients were recruited for the study from Zhejiang Cancer Hospital, all of whom were treated with gefitinib or erlotinib after failure to prior chemotherapy. We detected the genotype of peripheral blood lymphocytes of patients with GNAS1 T393C polymorphism through polymerase chain reaction (PCR). Statistical analysis was performed by SPSS version 18.0.

RESULTS

The overall response rate was 29.3%. No significant associations were found among GNAS1 T393C polymorphism and the objective response rate. The disease control rate of patients with GNAS1 T393C CC genotype was lower than that of patients with variant genotype (TT or CT) (46.2% vs 73.8%, P=0.039). Univariate analysis identified gender, smoking history, histology and GNAS1 T393C polymorphism as predictive marker of PFS (P=0.04, P<0.001, P<0.001 and P=0.005). Multivariate analysis of factors, including smoking history, performance status score, histology, GNAS1 T393C polymorphism demonstrated that GNAS1 T393C polymorphism was correlated independently with PFS (P=0.007).

CONCLUSIONS

Our data suggest the role of GNAS1 T393C CC genotype as a poor predictive marker both of DCR and PFS in advanced NSCLC patients treated with tyrosine kinase inhibitor.

Autophagy contributes to gefitinib-induced glioma cell growth inhibition

Epidermal growth factor receptor tyrosine kinase inhibitors, including gefitinib, have been evaluated in patients with malignant gliomas. However, the molecular mechanisms involved in gefitinib-mediated anticancer effects against glioma are incompletely understood. In the present study, the cytostatic potential of gefitinib was demonstrated by the inhibition of glioma cell growth, long-term clonogenic survival, and xenograft tumor growth. The cytostatic consequences were accompanied by autophagy, as evidenced by monodansylcadaverine staining of acidic vesicle formation, conversion of microtubule-associated protein-1 light chain 3-II (LC3-II), degradation of p62, punctate pattern of GFP-LC3, and conversion of GFP-LC3 to cleaved-GFP. Autophagy inhibitor 3-methyladenosine and chloroquine and genetic silencing of LC3 or Beclin 1 attenuated gefitinib-induced growth inhibition. Gefitinib-induced autophagy was not accompanied by the disruption of the Akt/mammalian target of rapamycin signaling. Instead, the activation of liver kinase-B1/AMP-activated protein kinase (AMPK) signaling correlated well with the induction of autophagy and growth inhibition caused by gefitinib. Silencing of AMPK suppressed gefitinib-induced autophagy and growth inhibition. The crucial role of AMPK activation in inducing glioma autophagy and growth inhibition was further supported by the actions of AMP mimetic AICAR. Gefitinib was shown to be capable of reducing the proliferation of glioma cells, presumably by autophagic mechanisms involving AMPK activation.

Molecular mechanism of apoptosis induction in skin cancer cells by the centipedegrass extract

Background

Centipedegrass extract (CGE) is mainly composed of maysin and its derivatives, which are recognized internationally as natural compounds. Compared to other flavonoids, maysin has a unique structure in that mannose is bound to the flavonoid backbone. CGE exhibits some biological properties in that it can function as an anti-oxidant, anti-inflammatory, anti-adipogenic, and insecticidal. Whether CGE has other biological functions, such as anti-cancer activity, is unknown.

Methods

B16F1 (mouse) and SKMEL-5 (human) cells were treated with CGE, and their subsequent survival was determined using MTT assay. We performed a cell cycle analysis using propidium iodide (PI), and detected apoptosis using double staining with annexin V-FITC/PI. In addition, we examined mitochondrial membrane potentials using flow cytometry, as well as signaling mechanisms with an immunoblotting analysis.

Results

CGE inhibited skin cancer cell growth by arresting the cell cycle in the G₂/M phase, and increased both early and late apoptotic cell populations without affecting normal cells. Furthermore, we observed mitochondrial transmembrane depolarization, increased cytochrome-c release, caspase-3 and caspase-7 activation, and increased poly ADP-ribose polymerase degradation. CGE also downregulated activation of p-AKT, p-glycogen synthase kinase-3β (GSK-3β), and p-BAD in a time-dependent manner. LY294002 inhibition of phosphoinositide 3-kinase (PI3K) significantly sensitized skin cancer cells, which led to an increase in CGE-induced apoptosis.

Conclusions

CGE controlled skin cancer cell growth by inhibiting the PI3K/AKT/GSK-3β signaling pathway and activating the effector caspases. This study is the first to demonstrate anti-cancer properties for CGE, and that CGE may be an effective therapeutic agent for treating skin cancer.

Tumor derived mutations of protein tyrosine phosphatase receptor type k affect its function and alter sensitivity to chemotherapeutics in glioma

Poor prognosis and resistance to therapy in malignant gliomas is mainly due to the highly dispersive nature of glioma cells. This dispersive characteristic results from genetic alterations in key regulators of cell migration and diffusion. A better understanding of these regulatory signals holds promise to improve overall survival and response to therapy. Using mapping arrays to screen for genomic alterations in gliomas, we recently identified alterations of the protein tyrosine phosphatase receptor type kappa gene (PTPRK) that correlate to patient outcomes. These PTPRK alterations are very relevant to glioma biology as PTPRK can directly sense cell–cell contact and is a dephosphorylation regulator of tyrosine phosphorylation signaling, which is a major driving force behind tumor development and progression. Subsequent sequencing of the full length PTPRK transcripts revealed novel PTPRK gene deletion and missense mutations in numerous glioma biopsies. PTPRK mutations were cloned and expressed in PTPRK-null malignant glioma cells. The effect of these mutations on PTPRK anti-oncogenic function and their association with response to anti-glioma therapeutics, such as temozolomide and tyrosine kinase inhibitors, was subsequently analyzed using in vitro cell-based assays. These genetic variations altered PTPRK activity and its post-translational processing. Reconstitution of wild-type PTPRK in malignant glioma cell lines suppressed cell growth and migration by inhibiting EGFR and β-catenin signaling and improved the effect of conventional therapies for glioma. However, PTPRK mutations abrogated tumor suppressive effects of wild-type PTPRK and altered sensitivity of glioma cells to chemotherapy.

Induction of apoptosis by luteolin involving akt inactivation in human 786-o renal cell carcinoma cells

There is a growing interest in the health-promoting effects of natural substances obtained from plants. Although luteolin has been identified as a potential therapeutic and preventive agent for cancer because of its potent cancer cell-killing activity, the molecular mechanisms have not been well elucidated. This study provides evidence of an alternative target for luteolin and sheds light on the mechanism of its physiological benefits. Treatment of 786-O renal cell carcinoma (RCC) cells (as well as A498 and ACHN) with luteolin caused cell apoptosis and death. This cytotoxicity was caused by the downregulation of Akt and resultant upregulation of apoptosis signal-regulating kinase-1 (Ask1), p38, and c-Jun N-terminal kinase (JNK) activities, probably via protein phosphatase 2A (PP2A) activation. In addition to being a concurrent substrate of caspases and event of cell death, heat shock protein-90 (HSP90) cleavage might also play a role in driving further cellular alterations and cell death, at least in part, involving an Akt-related mechanism. Due to the high expression of HSP90 and Akt-related molecules in RCC and other cancer cells, our findings suggest that PP2A activation might work in concert with HSP90 cleavage to inactivate Akt and lead to a vicious caspase-dependent apoptotic cycle in luteolin-treated 786-O cells.

Purine nucleoside analog--sulfinosine modulates diverse mechanisms of cancer progression in multi-drug resistant cancer cell lines

Achieving an effective treatment of cancer is difficult, particularly when resistance to conventional chemotherapy is developed. P-glycoprotein (P-gp) activity governs multi-drug resistance (MDR) development in different cancer cell types. Identification of anti-cancer agents with the potential to kill cancer cells and at the same time inhibit MDR is important to intensify the search for novel therapeutic approaches. We examined the effects of sulfinosine (SF), a quite unexplored purine nucleoside analog, in MDR (P-gp over-expressing) non-small cell lung carcinoma (NSCLC) and glioblastoma cell lines (NCI-H460/R and U87-TxR, respectively). SF showed the same efficacy against MDR cancer cell lines and their sensitive counterparts. However, it was non-toxic for normal human keratinocytes (HaCaT). SF induced caspase-dependent apoptotic cell death and autophagy in MDR cancer cells. After SF application, reactive oxygen species (ROS) were generated and glutathione (GSH) concentration was decreased. The expression of key enzyme for GSH synthesis, gamma Glutamyl-cysteine-synthetase (γGCS) was decreased as well as the expression of gst-π mRNA. Consequently, SF significantly decreased the expression of hif-1α, mdr1 and vegf mRNAs even in hypoxic conditions. SF caused the inhibition of P-gp (coded by mdr1) expression and activity. The accumulation of standard chemotherapeutic agent – doxorubicin (DOX) was induced by SF in concentration- and time-dependent manner. The best effect of SF was obtained after 72 h when it attained the effect of known P-gp inhibitors (Dex-verapamil and tariquidar). Accordingly, SF sensitized the resistant cancer cells to DOX in subsequent treatment. Furthermore, SF decreased the experssion of vascular endothelial growth factor (VEGF) on mRNA and protein level and modulated its secretion. In conclusion, the effects on P-gp (implicated in pharmacokinetics and MDR), GSH (implicated in detoxification) and VEGF (implicated in tumor-angiogenesis and progression) qualify SF as multi-potent anti-cancer agent, which use must be considered, in particular for resistant malignancies.