Akt1 inhibition by RNA interference sensitizes human non-small cell lung cancer cells to cisplatin

Mechanism of Taxanes in the Treatment of Lung Cancer Based on Network Pharmacology and Molecular Docking

Taxanes are natural compounds for the treatment of lung cancer, but the molecular mechanism behind the effects is unclear. In the present study, through network pharmacology and molecular docking, the mechanism of the target and pathway of taxanes in the treatment of lung cancer was studied. The taxanes targets were determined by PubChem database, and an effective compounds-targets network was constructed. The GeneCards database was used to determine the disease targets of lung cancer, and the intersection of compound targets and disease targets was obtained. The Protein-Protein Interaction (PPI) network of the intersection targets was analyzed, and the PPI network was constructed by Cytoscape 3.6.0 software. The hub targets were screened according to the degree value, and the binding activity between taxanes and hub targets was verified by molecular docking. The results showed that eight taxane-active compounds and 444 corresponding targets were screened out, and 131 intersection targets were obtained after mapping with lung cancer disease targets. The hub targets obtained by PPI analysis were TP53, EGFR, and AKT1. Gene Ontology (GO) biological function enrichment analysis obtained 1795 biological process (BP) terms, 101 cellular component (CC) terms, and 164 molecular function (MF) terms. There were 179 signaling pathways obtained by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Twenty signaling pathways were screened out, mainly pathways in cancer, proteoglycans in cancer pathway, microRNAs in cancer pathway, and so on. Molecular docking shows that the binding energies of eight taxanes with TP53, EGFR, and AKT1 targets were less than -8.8 kcal/mol, taxanes acts on TP53, EGFR, and AKT1 targets through pathways in cancer, proteoglycans in cancer pathway and microRNAs in cancer pathway, and plays a role in treating lung cancer in biological functions such as protein binding, enzyme binding, and identical protein binding.

Ferroptosis as a Potential Cell Death Mechanism Against Cisplatin-Resistant Lung Cancer Cell Line

Purpose: Drug resistance is a challenging issue in cancer chemotherapy. Cell death induction is one of the main strategies to overcome chemotherapy resistance. Notably, ferroptosis has been considered a critical cell death mechanism in recent years. Accordingly, in this study, the different cell death strategies focused on ferroptosis have been utilized to overcome cisplatin resistance in an in vitro lung cancer model. Methods: The physiological functions of Akt1 and GPX4, as critical targets for ferroptosis and apoptosis induction, were suppressed by siRNA or antagonistic agents in resistant A549 cells. Afterward, the interventions' impacts on cell viability and reactive oxygen species (ROS) amount were analyzed by flow cytometry. Moreover, the alteration in the relevant gene and protein expression levels were quantified using Real-time PCR and western blot methods. Results: The result showed that the treatment with Akt1 siRNA reversed the cisplatin resistance in the A549 cell line through the induction of apoptosis. Likewise, the combination treatment of the GPX4 siRNA or FIN56 as ferroptosis inducers alongside cisplatin elevated ROS's cellular level, reduced the cellular antioxidant genes level and increased the cisplatin cytotoxic effect. Conclusion: In conclusion, our study indicated that ferroptosis induction can be considered a promising cell death strategy in cisplatin-resistant cancer cells.

Network Pharmacology and Molecular Docking Analysis on Molecular Targets and Mechanisms of Aidi Injection Treating of Nonsmall Cell Lung Cancer

Background. Aidi injection (ADI) is a compound preparation injection of Chinese herbs used to treat patients of nonsmall cell lung cancer (NSCLC) in China. This study aimed to reveal the mechanism of ADI in the treatment of NSCLC by using network pharmacology and molecular docking. Methods. The related targets of ADI and NSCLC were obtained from multiple databases. The network diagram of disease-drug-components-targets (DDCT) and protein-protein interaction (PPI) was constructed to screen key targets. Then, the key targets and main signaling pathways were screened by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Next, in order to validate the results of network pharmacology, expression analysis and survival analysis of key genes were performed. Finally, we carried out the technology of molecular docking to further validate the accuracy of the above results. Results. A total of 207 targets of ADI and 5282 targets of NSCLC were obtained finally. Through the construction of DDCT and PPI network diagrams, 28 key targets were finally obtained. The results of the KEGG enrichment analysis indicated that multiple signaling pathways were associated with NSCLC, which included the MAPK signaling pathway, the IL-17 signaling pathway, and the PI3K/AKT signaling pathway. The key genes in the signaling pathway mainly include TP53, CASP3, MMP9, AKT1, PTGS2, and MAPK1. The results of differently expressed analysis of key genes showed that TP53, CASP3, MMP9, AKT1, PTGS2, and MAPK1 had statistical differences in lung squamous cell carcinoma (LUSC) compared with normal tissue $\left(p<0.001\right)$ . In lung adenocarcinoma (LUAD), the expression of TP53, CASP3, MMP9, AKT1, and PTGS2 had statistical differences compared with normal tissue $\left(p<0.001\right)$ , while the expression of MAPK1 had no statistical difference $\left(p>0.05\right)$ . The results of survival analysis of key genes showed that AKT1, MAPK1, CASP3, MMP9, TP53, and PTGS2 had statistical differences in the OS or RFS of NSCLC patients $\left(p<0.05\right)$ . In addition, the results of molecular docking indicated that the key genes and the main components have good docking activity. Conclusions. This study revealed the potential mechanism of ADI in the treatment of NSCLC with multipathways and multitargets and provided a scientific basis for the in-depth study of ADI in the treatment of NSCLC.

The sodium/myo-inositol co-transporter SLC5A3 promotes non-small cell lung cancer cell growth

Identification of novel molecular signaling targets for non-small cell lung cancer (NSCLC) is important. The present study examined expression, functions and possible underlying mechanisms of the sodium/myo-inositol co-transporter SLC5A3 in NSCLC. The Cancer Genome Atlas (TCGA) database and local NSCLC tissue results demonstrated that SLC5A3 expression in NSCLC tissues (including patient-derived primary NSCLC cells) was significantly higher than that in normal lung tissues and lung epithelial cells. In primary NSCLC cells and immortalized lines, SLC5A3 depletion, using small hairpin RNA (shRNA) and CRSIRP/Cas9 methods, robustly impeded cell proliferation and migration, simultaneously provoking cell cycle arrest and apoptosis. Conversely, ectopic overexpression of SLC5A3 further enhanced proliferation and migration in primary NSCLC cells. The intracellular myo-inositol contents and Akt-mTOR activation were largely inhibited by SLC5A3 silencing or knockout (KO), but were augmented following SLC5A3 overexpression in primary NSCLC cells. Significantly, SLC5A3 KO-induced anti-NSCLC cell activity was largely ameliorated by exogenously adding myo-inositol or by a constitutively-active Akt construct. By employing the patient-derived xenograft (PDX) model, we found that the growth of subcutaneous NSCLC xenografts in nude mice was largely inhibited by intratumoral injection SLC5A3 shRNA adeno-associated virus (AAV). SLC5A3 silencing, myo-inositol depletion, Akt-mTOR inactivation and apoptosis induction were detected in SLC5A3 shRNA virus-injected NSCLC xenograft tissues. Together, elevated SLC5A3 promotes NSCLC cell growth possibly by maintaining myo-inositol contents and promoting Akt-mTOR activation.

Uncovering the Anti-Lung-Cancer Mechanisms of the Herbal Drug FDY2004 by Network Pharmacology

With growing evidence on the therapeutic efficacy and safety of herbal drugs, there has been a substantial increase in their application in the lung cancer treatment. Meanwhile, their action mechanisms at the system level have not been comprehensively uncovered. To this end, we employed a network pharmacology methodology to elucidate the systematic action mechanisms of FDY2004, an anticancer herbal drug composed of Moutan Radicis Cortex, Persicae Semen, and Rhei Radix et Rhizoma, in lung cancer treatment. By evaluating the pharmacokinetic properties of the chemical compounds present in FDY2004 using herbal medicine-associated databases, we identified its 29 active chemical components interacting with 141 lung cancer-associated therapeutic targets in humans. The functional enrichment analysis of the lung cancer-related targets of FDY2004 revealed the enriched Gene Ontology terms, involving the regulation of cell proliferation and growth, cell survival and death, and oxidative stress responses. Moreover, we identified key FDY2004-targeted oncogenic and tumor-suppressive pathways associated with lung cancer, including the phosphatidylinositol 3-kinase-Akt, mitogen-activated protein kinase, tumor necrosis factor, Ras, focal adhesion, and hypoxia-inducible factor-1 signaling pathways. Overall, our study provides novel evidence and basis for research on the comprehensive anticancer mechanisms of herbal medicines in lung cancer treatment.

Quercetin Inhibits the Proliferation and Metastasis of Human Non-Small Cell Lung Cancer Cell Line: The Key Role of Src-Mediated Fibroblast Growth Factor-Inducible 14 (Fn14)/ Nuclear Factor kappa B (NF-κB) pathway

Background

Quercetin (Que) is reported to induce apoptosis of lung cancer cells. Src is closely related to the progression of non-small cell lung cancer (NSCLC) and can be modulated by Que in macrophages. In the current study, the interaction between Que and Src signaling in NSCLC cells was explored to explain the anti-NSCLC function of Que.

Material/Methods

NSCLC cell line HCC827 was subjected to the administrations of Que at different concentrations. The effect of Que on tumor cell proliferation was detected using MTT and colony formation assays. Then the effect on the migration and invasion abilities was assessed using scratch and Transwell assays. At molecular level, the changes in Src/Fn14/NF-κB signaling were determined using western blotting assays. The role of Src in the function of Que was further explored by inducing the expression of Src gene in NSCLC cells before Que administration. The results of the in vitro assays were verified using a NSCLC mice model.

Results

Que inhibited the proliferation and anchorage-independent growth of NSCLC cells. Additionally, Que delayed in the gap closure rate in scratch assays and decreased the membrane-penetrating cell number in Transwell assays. At a molecular level, Que suppressed the expression of Src, which subsequently inhibited Fn14/NF-κB signaling. In in vivo assays, Que inhibited the growth of solid tumors. After the overexpression of Src in NSCLC cells, the anti-NSCLC effect of Que was blocked by inducing NSCLC proliferation and metastasis, and by activating Fn14/NF-κB signaling. Moreover, the induced level of Src promoted the growth and metastasis potential of solid tumors in mice.

Conclusions

Que exerted the anti-NSCLC effect by inhibiting Src-mediated Fn14/NF-κB pathway both in vitro and in vivo.

Folic acid conjugation improves the bioavailability and chemosensitizing efficacy of curcumin-encapsulated PLGA-PEG nanoparticles towards paclitaxel chemotherapy

Nanoencapsulation has emerged as a novel strategy to enhance the pharmacokinetic and therapeutic potential of conventional drugs. Recent studies from our lab have established the efficacy of curcumin in sensitizing cervical cancer cells and breast cancer cells towards paclitaxel and 5-FU chemotherapy respectively. Factors that hinder the clinical use of curcumin as a sensitizer or therapeutic agent include its poor bioavailability and retention time. Earlier reports of improvement in bioavailability and retention of drugs upon nanoencapsulation have motivated us in developing various nanoformulations of curcumin, which were found to exhibit significant enhancement in bioavailability and retention time as assessed by our previous in vitro studies. Among the various formulations tested, curcumin-entrapped in PLGA-PEG nanoparticles conjugated to folic acid (PPF-curcumin) displayed maximum cell death. In the present study, we have demonstrated the efficacy of this formulation in augmenting the bioavailability and retention time of curcumin, in vivo, in Swiss albino mice. Further, the acute and chronic toxicity studies proved that the formulation is pharmacologically safe. We have also evaluated its potential in chemosensitizing cervical cancer cells to paclitaxel and have verified the results using cervical cancer xenograft model in NOD-SCID mice. Folic acid conjugation significantly enhanced the efficacy of curcumin in down-regulating various survival signals induced by paclitaxel in cervical cancer cells and have considerably improved its potential in inhibiting the tumor growth of cervical cancer xenografts. The non-toxic nature coupled with improved chemosensitization potential makes PPF-curcumin a promising candidate formulation for clinical trials.

Protein kinase B: emerging mechanisms of isoform-specific regulation of cellular signaling in cancer

The serine/threonine protein kinase B (PKB), also known as Akt, is one of the multifaceted kinases in the human kinome, existing in three isoforms. PKB plays a vital role in phosphoinositide 3-kinase (PI3K)-mediated oncogenesis in various malignancies and is one of the attractive targets for cancer drug discovery. Recent studies have shown that the functional significance of an individual isoform of PKB is not redundant in cancer. It has been found that PKB isoforms play distinct roles in the regulation of cellular invasion and migration during tumorigenesis. PKB activation plays a central role during epithelial-mesenchymal transition, a cellular program required for the cancer cell invasion and migration. However, the differential behavior of each PKB isoform has been shown in the regulation of epithelial-mesenchymal transition. Recent studies have suggested that PKBα (Akt1) plays a conflicting role in tumorigenesis by acting either as a pro-oncogenic factor by suppressing the apoptotic machinery or by restricting tumor invasion. PKBβ (Akt2) promotes cell migration and invasion and similarly PKBγ (Akt3) has been reported to promote tumor migration. As PKB is known for its pro-oncogenic properties, it needs to be unraveled how three isoforms of PKB compensate during tumor progression. In this review, we attempted to sum up how different isoforms of PKB play a role in cancer progression, metastasis, and drug resistance.

Enhanced Sensitivity to Sunitinib by Inhibition of Akt1 Expression in Human Castration-resistant Prostate Cancer PC3 Cells Both In Vitro and In Vivo

OBJECTIVE

To investigate whether antitumor activity of sunitinib is enhanced by silencing Akt1 in a human castration-resistant prostate cancer PC3 model.

MATERIALS AND METHODS

We initially established PC3 in which the expression vector containing a short hairpin ribonucleic acid targeting Akt1 was introduced (PC3/sh-Akt1). Changes in various phenotypes of PC3/sh-Akt1 after treatment with sunitinib were compared with those of PC3 transfected with control vector alone (PC3/C) both in vitro and in vivo.

RESULTS

When cultured in the standard medium, in vitro growth of PC3/sh-Akt1 was almost similar to that of PC3/C. However, compared with PC3/C, PC3/sh-Akt1 showed a significantly higher sensitivity to sunitinib, accompanying impaired phosphorylation of p44/42 mitogen-activated protein kinase, downregulation of Bcl-2, and upregulation of Bax. In addition, treatment with sunitinib significantly suppressed the migration ability of PC3/sh-Akt1 compared with that of PC3/C. In vivo, administration of sunitinib induced the significantly marked growth inhibition of PC3/sh-Akt1 compared with that of PC3/C, and apoptotic index in PC3/sh-Akt1 tumor in mice treated with sunitinib was significantly greater than that in PC3/C tumor.

CONCLUSION

Combined treatment with Akt1 inhibitor and sunitinib could be a promising therapeutic approach for men with castration-resistant prostate cancer.

Functional specificity of Akt isoforms in cancer progression

Akt/PKB kinases are central mediators of cell homeostasis. There are three highly homologous Akt isoforms, Akt1/PKBα, Akt2/PKBβ and Akt3/PKBγ. Hyperactivation of Akt signaling is a key node in the progression of a variety of human cancer, by modulating tumor growth, chemoresistance and cancer cell migration, invasion and metastasis. It is now clear that, to understand the mechanisms on how Akt affects specific cancer cells, it is necessary to consider the relative importance of each of the three Akt isoforms in the altered cells. Akt1 is involved in tumor growth, cancer cell invasion and chemoresistance and is the predominant altered isoform found in various carcinomas. Akt2 is related to cancer cell invasion, metastasis and survival more than tumor induction. Most of the Akt2 alterations are observed in breast, ovarian, pancreatic and colorectal carcinomas. As Akt3 expression is limited to some tissues, its implication in tumor growth and resistance to drugs mostly occurs in melanomas, gliomas and some breast carcinomas. To explain how Akt isoforms can play different or even opposed roles, three mechanisms have been proposed: tissue-specificity expression/activation of Akt isoforms, distinct effect on same substrate as well as specific localization through the cyto-skeleton network. It is becoming clear that to develop an effective anticancer Akt inhibitor drug, it is necessary to target the specific Akt isoform which promotes the progression of the specific tumor.

Dasatinib enhances cisplatin sensitivity in human esophageal squamous cell carcinoma (ESCC) cells via suppression of PI3K/AKT and Stat3 pathways

The clinical efficacy of cisplatin in esophageal squamous cell carcinoma (ESCC) treatment remains undesirable. Src, a non-receptor tyrosine kinase involved in multiple fields of tumorigenesis, recently has been indicated as a promising therapeutic target in the treatment of solid tumors including ESCC. However, whether inhibition of Src activity can increase cisplatin efficacy in ESCC cells remains unknown. The present study found that inhibition of Src by its inhibitor-dasatinib sensitized ESCC cells to cisplatin in vitro. Our data also suggest a likely mechanism for this synergy that dasatinib reduces expression of critical oncogenic members of the signaling pathways, such as AKT or Stat3, and cisplatin-resistant molecules, such as ERCC1 and BRCA1, under the control of Src. Furthermore, dasatinib could sensitize ESCC cells to another platin-based agent, carboplatin. Therefore, this study provides a potential target for improving cisplatin efficacy in ESCC therapy.

[Effect of PI3K/AKT pathway on cisplatin resistance in non-small cell lung cancer]

Accumulating evidences indicate that aberrant activation of PI3K/AKT pathway in non-small cell lung cancer plays a vital role in tumor cell proliferation,apoptosis, and survival including drug resistance. Cisplatin as first-line chemotherapy are in widespread clinical use in patients with non-small cell lung cancer, however, the development of cisplatin resistance significantly impedes its clinic efficacy. Cisplatin resistance is a complicated process that various mechanisms participating in to interact, of which PI3K/AKT pathway keeping sustained activated is one of the most important reasons. This article reviewed the progress of research on the relationship between PI3K/AKT pathway and cisplatin resistance.

Strategic targeting of the PI3K-NFκB axis in cisplatin-resistant NSCLC

Chemoresistance is a major therapeutic challenge to overcome in NSCLC, in order to improve the current survival rates of<15% at 5 years. We and others have shown increased PI3K signaling in NSCLC to be associated with a more aggressive disease, and a poorer prognosis. In this study, targeted inhibition of three strategic points of the PI3K-NFκB axis was performed with the aim of exploiting vulnerabilities in cisplatin-resistant NSCLC cells. Cisplatin-resistant cell lines were previously generated through prolonged exposure to the drug. Expression of PI3K and NFκB pathway-related genes were compared between cisplatin-resistant cells and their matched parent cells using a gene expression array, qRT-PCR, DNA sequencing, western blot, and immunofluorescence. Targeted inhibition was performed using GDC-0980, a dual PI3K-mTOR inhibitor currently in Phase II clinical trials in NSCLC, and DHMEQ, an inhibitor of NFκB translocation which has been used extensively both in vitro and in vivo. Effects of the two inhibitors were assessed by BrdU proliferation assay and multiparameter viability assay. NFKBIA was shown to be 12-fold overexpressed in cisplatin-resistant cells, with no mutations present in exons 3, 4, or 5 of the gene. Corresponding overexpression of IκBα was also observed. Treatment with DHMEQ (but not GDC-0980) led to significantly enhanced effects on viability and proliferation in cisplatin-resistant cells compared with parent cells. We conclude that NFκB inhibition represents a more promising strategy than PI3K-mTOR inhibition for treatment in the chemoresistance setting in NSCLC.

Knockdown of CABYR-a/b increases chemosensitivity of human non-small cell lung cancer cells through inactivation of Akt

CABYR is a calcium-binding tyrosine phosphorylation-regulated protein that was identified as a novel cancer testis antigen in lung cancer in our previous study. However, the role of CABYR as a driver of disease progression or as a chemosensitizer is poorly understood. This study sought to investigate the relationship between the expression levels of CABYR-a/b, which are the two predominant isoforms of the five isoform proteins encoded by CABYR, and chemosensitivity in non-small cell lung cancer cells. We found that the short hairpin RNA-mediated knockdown of CABYR-a/b significantly inhibited the proliferation of NCI-H460 and A549 cells and resulted in the attenuation of Akt phosphorylation, which is constitutively active in lung cancer cells. The silencing of CABYR-a/b expression notably impacted the downstream components of the Akt pathways: decreasing the phospho-GSK-3β (Ser9) levels and increasing the expression of the p53 and p27 proteins. Furthermore, CABYR-a/b knockdown led to a significant increase in chemosensitivity in response to chemotherapeutic drugs and drug-induced apoptosis, both in vitro and in vivo. Conversely, the transient transfection of CABYR-a/b-depleted cells with constitutively active Akt partially restored the resistance to cisplatin and paclitaxel and significantly decreased the activation of GSK-3β and cleaved PARP. Taken together, our results suggest that the inhibition of CABYR-a/b is a novel method to improve the apoptotic response and chemosensitivity in lung cancer and that this cancer testis antigen is an attractive target for lung cancer drug development.

IMPLICATIONS

Suppression of CABYR-a/b expression increases chemosensitivity of lung cancer cells by inhibiting Akt activity.

miR-101 sensitizes A549 NSCLC cell line to CDDP by activating caspase 3-dependent apoptosis

MicroRNA-101 (miR-101) is evidently downregulated in several types of cancer, including non-small cell lung cancer (NSCLC), and is crucial in sensitizing cells to chemotherapy drugs. The aim of the present study was to investigate the correlation between miR-101 and chemosensitivity in the A549 NSCLC cell line. Here, we used the human A549 cell line for transfection with an miR-101 overexpressing vector and detected the cytotoxic acticity, proliferation and apoptosis of cis-diaminedichloroplatinum (CDDP) in A549-miR-101 and A549-mock cells. We demonstrated that overexpression of miR-101 sensitized A549 cells to CDDP, one of the most frequently used agents in curing or controlling NSCLC and enhanced CDDP-induced cell death and caspase 3-dependent apoptosis. In addition, miR-101 facilitated the inhibitory role of CDDP in A549 cell colony formation. Overall, the results of the present study demonstrated that miR-101 sensitizes the A549 NSCLC cell line to CDDP via the activation of caspase 3-dependent apoptosis.

Synergy of Taxol and rhein lysinate associated with the downregulation of ERK activation in lung carcinoma cells

In previous studies we observed that rhein lysinate (RHL), a salt of rhein and lysine that is easily dissolved in water, inhibited the growth of tumor cells in breast cancer, ovarian cancer, hepatocellular carcinoma and cervical cancer. The present study aimed to investigate the effects of RHL on H460 and A549 non-small cell lung cancer (NSCLC) cells using a combination of RHL and Taxol. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was used to determine the growth inhibition effect of the drugs in the H460 and A549 cells. Cell apoptosis was analyzed by flow cytometry combined with fluorescein-isothiocyanate-Annexin V/propidium iodide (PI) staining. The expression levels of proteins were detected by western blotting. There was a significant reduction in the proliferation of the NSCLC cell lines treated with a combination of Taxol and RHL. The overall growth inhibition was directly correlated with apoptotic cell death. RHL potentiated Taxol-induced cell killing by reducing extracellular signal-regulated kinase (ERK) activity and increasing the levels of cleaved poly(ADP-ribose) polymerase (PARP) and caspase-3. Notably, the results for the Bcl-2 and NF-κB proteins also showed downregulation in the combined treatment group compared with the single-agent treatment and the untreated control groups. The present results showed that RHL potentiates the growth inhibition induced by Taxol in NSCLC cells and showed that this synergy may be associated with the downregulation of ERK activation.

Direct TGF-β1 signaling between activated platelets and pancreatic cancer cells primes cisplatin insensitivity

The exact mechanisms underlying chemotherapy insensitivity in pancreatic cancer remain largely unclear. The dynamic cross talk between tumors and their microenvironment is an important determinant of cancer chemosensitivity. However, whether additional signals provided during the intravascular transit of tumor cells affect the sensitivity of pancreatic cancer cells to chemotherapy is unknown. We have found that activated platelet-cancer cell interactions are sufficient to prime cisplatin (CDDP) insensitivity in pancreatic cancer cells. Activated platelet-derived TGF-β1 rather than direct platelet-tumor cell contacts stimulates PI3K/Akt and MEK/Erk signaling in pancreatic cancer cells, resulting in reduction of CDDP sensitivity in these cells. Therefore, the platelet-tumor cell interactions and the relevant signaling pathways that prime CDDP insensitivity may be potential targets for adjuvant chemotherapy for pancreatic cancer.

p73 expression is associated with cellular chemosensitivity in human non-small cell lung cancer cell lines

p73 is a member of the p53 tumor suppressor protein family and induces apoptosis in tumor cells that lack functional p53. It has been demonstrated that methylation of CpG islands in the promoter and exon 1 region may result in silencing of the p73 gene. The aim of this study was to investigate the correlation between p73 gene expression and chemosensitivity in non-small cell lung cancer (NSCLC) cell lines. The expression of the p73 transcript in six NSCLC cell lines was investigated by reverse transcription-polymerase chain reaction (RT-PCR). The methylation status in these cell lines was determined by methylation-specific PCR (MSP) analysis. An in vitro demethylation assay was conducted using the DNA methyltransferase inhibitor 5-aza-2-deoxycytidine (5-aza-dC). Restored expression of p73 in the human lung squamous cell carcinoma cell line C57, both at the mRNA and protein level, was investigated by RT-PCR and immunohistochemistry, respectively. A colony formation assay was used to measure the surviving fraction of the C57 cell line. Transcript silencing of the p73 gene in the six NSCLC cell lines was observed and related to aberrant methylation. The expression of the p73 transcript and protein in the C57 cell line was restored by 5-aza-dC. The surviving fraction for colony formation in C57 cells pre-treated with 5-aza-dC was 0.059±0.006, which was significantly different from that of the control group (0.12±0.008; P<0.05). Our data demonstrated a significant correlation between expression of p73 and cellular chemosensitivity in NSCLC.

Differential effects of AKT1(p.E17K) expression on human mammary luminal epithelial and myoepithelial cells

Recently, we identified a somatic mutation in AKT1, which results in a glutamic acid to lysine substitution (p.Glu17Lys or E17K). E17K mutations appear almost exclusively in breast cancers of luminal origin. Cellular models involving cell lines such as human mammary epithelial and MCF10 are model systems that upon transformation lead to rare forms of human breast cancer. Hence, we studied the effects of E17K using a clinically pertinent luminal cell line model while providing evidence to explain why E17K mutations do not occur in the mammary myoepithelium. Thus the purpose of our study was to perform a functional and differential proteomics study to assess the role of AKT1(E17K) in the development of breast cancer. We used a set of genetically matched nontumorigenic and tumorigenic mammary luminal and myoepithelial cells. We demonstrated that in myoepithelial cells, expression of E17K inhibited growth, migration, and protein synthesis compared with wild-type AKT1. In luminal cells, E17K enhanced cell survival and migration, possibly offering a selective advantage in this type of cell. However, antineoplastic effects of E17K in luminal cells, such as inhibition of growth and protein synthesis, may ultimately be associated with favorable prognosis. Our study illustrates the importance of cellular context in determining phenotypic effects of putative oncogenic mutations.

Survivin expression in human lung cancer and the influence of its downregulation on the biological behavior of human lung cancer cells

The aim of the present study was to detect the expression of survivin in human lung cancer and to investigate the influence of its downregulation on the biological behavior of A549 lung cancer cells. The high expression of survivin in human lung cancer was verified by immunohistochemistry. Survivin small interfering RNA (siRNA) and unrelated sequence were synthesized and the siRNA lentiviral vector was constructed. The vector was transfected into A549 lung cancer cells, in which the clone with stable expression was screened out. We blocked the expression of survivin mRNA and protein by RNA interference (RNAi) technique. The downregulation of survivin mRNA and protein expression was confirmed by real-time quantitative PCR and western blotting. The proliferative activity and growth rate of A549 cells were determined by colony formation assay and mononuclear cell direct cytotoxicity assay (MTT assay). The reconstituted basement membrane (RBM) penetrating capacity was determined by cell invasion assay. The cell movement and migratory capacity were detected by wound-healing repair assay. The results showed that the sequence-specific siRNA significantly downregulated the expression of survivin at both the mRNA and protein levels. Downregulation of survivin expression dramatically decreased the invasive and metastatic capacities of the cells, suppressed the proliferation, decelerated the rate of growth, reduced the number of clones on soft agar and decreased the capacity of RBM penetration and migration. In conclusion, survivin, which plays an important role in carcinogenesis and development of lung cancer, can be effectively downregulated using the RNAi technique.

Chemotherapy-associated angiogenesis in neuroblastoma tumors

The influences of cytotoxic drugs on endothelial cells remain incompletely understood. Herein, we examined the effects of chemotherapeutic agents in experimental angiogenesis models and analyzed vessel densities in clinical neuroblastoma tumor samples. Cisplatin (20 to 500 ng/mL), doxorubicin (4 to 100 ng/mL), and vincristine (0.5 to 4 ng/mL), drugs commonly involved in neuroblastoma therapy protocols, induced pro-angiogenic effects in different angiogenesis models. They enhanced endothelial cell tube formation, endothelial cell sprouting from spheroids, formation of tip cells in the sprouting assay, expression of αvβ3 integrin, and vitronectin binding. All three drugs increased global cellular kinase phosphorylation levels, including the angiogenesis-relevant molecules protein kinase Cβ and Akt. Pharmacological inhibition of protein kinase Cβ or Akt upstream of phosphatidylinositol 3-kinase reduced chemotherapy-induced endothelial cell tube formation. Moreover, the investigated chemotherapeutics dose dependently induced vessel formation in the chick chorioallantoic membrane assay. Tumor samples from seven high-risk patients with neuroblastoma were analyzed for vessel density by IHC. Results revealed that neuroblastoma samples taken after chemotherapy consistently showed an enhanced microvessel density compared with the corresponding samples taken before chemotherapy. In conclusion, our data show that chemotherapy can activate endothelial cells by inducing multiple pro-angiogenic signaling pathways and exert pro-angiogenic effects in vitro and in vivo. Moreover, we report a previously unrecognized clinical phenomenon that might, in part, be explained by our experimental observations: chemotherapy-associated enhanced vessel formation in tumors from patients with neuroblastoma.

Atorvastatin sensitizes human non-small cell lung carcinomas to carboplatin via suppression of AKT activation and upregulation of TIMP-1

Platinum-based chemotherapy is the standard treatment for advanced non-small-cell lung carcinomas (NSCLCs). However, the antitumoral effect of carboplatin displays unsatisfactory in NSCLCs treatment due to the AKT pathway-mediated carboplatin insensitive in NSCLCs treatment. Previous studies have shown that statins have antitumor activity, but it is unknown whether atorvastatin can reverse carboplatin resistance in lung cancer. Treatment with atorvastatin and carboplatin reduced the growth of xenograft A549 tumors in nude mice and enhanced the survival rate compared with carboplatin alone. Atorvastatin in combination with carboplatin had stronger effects on growth inhibition and apoptosis of NSCLC than either agent used individually. Carboplatin conferred anti-invasive effect in NSCLC cells mainly through inhibition of AKT activity and resultant upregulation of TIMP-1. However, the inhibitory effect on AKT activity by carboplatin was short-term. Additional atorvastatin administration resulted in synergistic inhibition of NSCLC cell invasion and stimulation of TIMP-1 expression with carboplatin through stronger and persistent inhibition of AKT activity both in vivo and in vitro. The synergy of atorvastatin and carboplatin was confirmed using another human lung carcinoma cell line (H1299). Altogether, our data demonstrate that atorvastatin may overcome carboplatin resistance in lung cancer by suppressing AKT activity and upregulating TIMP-1. A combination of atorvastatin and carboplatin may be an effective strategy in clinical therapy against NSCLCs.

Effects and mechanism of downregulation of survivin expression by RNA interference on proliferation and apoptosis of lung cancer cells

The survivin protein, a member of the inhibitors of apoptosis (IAP) family, has gained popularity as a therapeutic target for cancer due to its selective expression in tumor cells and its significant involvement in tumor cell viability. The aim of this study was to investigate the effect of the survivin-small interfering RNA (siRNA) plasmid on survivin expression in the human lung cancer cell line, A549, and to observe its effects on apoptosis and proliferation of A549 cells. A549 human lung cancer cells were transfected with survivin-targeting siRNA. The downregulation of survivin expression was determined by real-time polymerase chain reaction and western blotting. The proliferation of A549 cells was determined by MTT assay. The apoptotic rate and cell cycle distribution were analyzed by flow cytometry (FCM). Caspase-9 activity was also detected to study the apoptosis of lung cancer cells induced by siRNA against survivin. The sequence-specific siRNA efficiently and specifically downregulated the expression of survivin at both the mRNA and protein levels. Downregulation of survivin expression dramatically suppressed the proliferation of A549 cells and arrested the cells at the G (1)/G (0) phase. Caspase-9 activity was significantly increased in A549 cells transfected with siRNA against survivin. In this study, we found that survivin-specific siRNA can efficiently suppress the expression of survivin, increase apoptosis and inhibit A549 cell proliferation. Our findings further indicate the possibility that the antitumor effects of survivin-siRNA are mediated through the activation of caspase-9.

Phospho-ΔNp63α/miR-885-3p axis in tumor cell life and cell death upon cisplatin exposure

The cisplatin-induced ATM-dependent phosphorylated (p)-ΔNp63α plays an important role in transcriptional regulation of specific genes encoding mRNAs and microRNAs (miRs) implicated in cell death, cell survival, and chemoresistance. The p-ΔNp63α-induced miR-885-3p functions as a critical regulator of MDM4, ATK1, BCL2, ATG16L2, ULK2, CASP2, and CASP3 mRNAs via pairing with their respective 'recognition' sequences. Cisplatin exposure modulated the levels of target proteins (reduced BCL2, AKT1, ATG16L2, and ULK2, while activated MDM4) in cisplatin-sensitive wild type ΔNp63α cells leading to distinct changes in cell viability. Finally, miR-885-3p modulated the cisplatin-induced TP53-dependent mitochondrial apoptosis by up regulation of MDM4 levels and down regulation of BCL2 levels in mitochondria. Altogether, our results support the notion that miR-885-3p might contribute in regulation of cell viability, apoptosis and/or autophagy in squamous cell carcinoma cells upon cisplatin exposure.

Roles of AKT1 and AKT2 in non-small cell lung cancer cell survival, growth, and migration

Although AKT ⁄ protein kinase B is constitutively active in nonsmall cell lung cancer (NSCLC) cells and is an attractive target for enhancing the cytotoxicity of therapeutic agents, the distinct roles of the AKT isoforms in NSCLC are largely unknown. In the present study, we investigated the roles of AKT1 and AKT2 in NSCLC cells using RNAi. The siRNA targeting of AKT1 or AKT2 effectively decreased protein levels of AKT1 and AKT2, respectively, in A549 and H460 cells. Cisplatin treatment of these cells increased apoptotic cell death compared with control. The siRNA-induced knockdown of AKT1 in H460 cells significantly decreased basal MEK⁄ ERK1 ⁄ 2 activity, resulting in nuclear factor-κB activation, whereas knockdown of AKT2 resulted in anti-apoptotic Bcl-2 family protein MCL-1 (MCL-1) cleavage, the collapse of mitochondrial membrane potential, cytochrome c release, and activation of the caspase cascade. Consequently, both siRNA treatments enhanced the chemosensitivity of H460 cells to cisplatin. However, neither AKT1 nor AKT2 siRNA treatment had any effect of p27 expression, and although both treatments tended to induced G₂ ⁄M phase arrest, the effect was not statistically significant. Treatment with AKT1 siRNA markedly decreased colony formation growth and migration, but AKT2 siRNA had no significant effects on these parameters. These data suggest that AKT1 and AKT2 both contribute to cell survival, albeit via different mechanisms, and that the effects on cell growth and migration are predominantly regulated by AKT1. These findings may aid in refining targeted strategies for the inhibition of AKT isoforms towards the sensitization of NSCLC cells to therapeutic agents.

Cationic drug-derived nanoparticles for multifunctional delivery of anticancer siRNA

Combined treatment of anticancer drugs and small interfering RNAs (siRNAs) have emerged as a new modality of anticancer therapy. Here, we describe a co-delivery system of anticancer drugs and siRNA in which anticancer drug-derived lipids form cationic nanoparticles for siRNA complexation. The anticancer drug mitoxantrone (MTO) was conjugated to palmitoleic acid, generating two types of palmitoleyl MTO (Pal-MTO) lipids: monopalmitoleyl MTO (mono-Pal-MTO) and dipalmitoleyl MTO (di-Pal-MTO). Among various lipid compositions of MTO, nanoparticles containing mono-Pal-MTO and di-Pal-MTO at a molar ratio of 1:1 (md11-Pal-MTO nanoparticles) showed the most efficient cellular delivery of siRNA, higher than that of Lipofectamine 2000. Delivery of red fluorescence protein-specific siRNA into B16F10-RFP cells using md11-Pal-MTO nanoparticles reduced the expression of RFP at both mRNA and protein levels, demonstrating silencing of the siRNA target gene. Moreover, delivery of Mcl-1-specific anticancer siRNA (siMcl-1) using md11-Pal-MTO enhanced antitumor activity in vitro, reducing tumor cell viability by 81% compared to a reduction of 68% following Lipofectamine 2000-mediated transfection of siMcl-1. Intratumoral administration of siMcl-1 using md11-Pal-MTO nanoparticles significantly inhibited tumor growth, reducing tumor size by 83% compared to untreated controls. Our results suggest the potential of md11-Pal-MTO multifunctional nanoparticles for co-delivery of anticancer siRNAs for effective combination therapy.

Up-regulation of extracellular signal-regulated kinase 1/2-dependent thymidylate synthase and thymidine phosphorylase contributes to cisplatin resistance in human non-small-cell lung cancer cells

Chemotherapy for advanced human non-small-cell lung cancer (NSCLC) includes platinum-containing compound such as cisplatin in combination with a second- or third-generation cytotoxic agent. 5-Fluorouracil (5-FU) belongs to antimetabolite chemotherapeutics, and its mechanism of cytotoxicity is involved in the inhibition of thymidylate synthase (TS). TS and thymidine phosphorylase (TP) are key enzymes of the pyrimidine salvage pathway. In this study, we have examined the molecular mechanism of TS and TP in regulating drug sensitivity to cisplatin in NSCLC cell lines. Cisplatin could increase the phosphorylation of mitogen-activated protein kinase kinase 1/2 (MKK1/2)-extracellular signal-regulated kinase 1/2 (ERK1/2) and the protein levels of TS and TP through enhancing the protein stability in A549 and H1975 cells. Blocking ERK1/2 activation by MKK1/2 inhibitor [U0126; 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene)] decreased TS and TP protein levels in both cell lines treated with cisplatin. Depletion of endogenous TS or TP expression by specific small interfering RNA transfection significantly increased cisplatin-induced cell death and growth inhibition. Combined treatment with 5-FU could decrease cisplatin-induced ERK1/2 activation and the induction of TS and TP, which subsequently resulted in synergistic cytotoxic effects. Enforced expression of constitutive active MKK1/2 vectors rescued the protein levels of phospho-ERK1/2, TS, and TP, and the cell viability that were decreased by cisplatin and 5-FU combination. In contrast, U0126 enhanced drug sensitivity to cisplatin and/or 5-FU in lung cancer cells. In conclusion, the up-regulation of ERK1/2-dependent TS and TP can protect human lung cancer cells from cisplatin-induced cytotoxicity.

PI3K/PTEN/AKT/mTOR pathway genetic variation predicts toxicity and distant progression in lung cancer patients receiving platinum-based chemotherapy

Non-small cell lung cancer (NSCLC) is still the leading cause of cancer-related deaths. The effect of the PI3K/PTEN/AKT/mTOR signaling pathway on cancer treatment, including NSCLC, has been well documented. In this study, we analyzed associations between genetic variations within this pathway and clinical outcomes following platinum-based chemotherapy in 168 patients with stage IIIB (wet) or stage IV NSCLC. Sixteen tagging SNPs in five core genes (PIK3CA, PTEN, AKT1, AKT2, and FRAP1) of this pathway and identified SNPs associated with development of toxicity and disease progression. We observed significantly increased toxicity for patients with PIK3CA:rs2699887 (OR: 3.86, 95% CI: 1.08-13.82). In contrast, a SNP in PTEN was associated with significantly reduced risk for chemotherapeutic toxicity (OR: 0.44, 95% CI: 0.20-0.95). We identified three SNPs in AKT1 resulting in significantly decreased risks of distant progression in patients carrying at least one variant allele with HRs of 0.66 (95% CI: 0.45-0.97), 0.52 (95% CI: 0.35-0.77), and 0.62 (95% CI: 0.42-0.91) for rs3803304, rs2498804, and rs1130214, respectively. Furthermore, these same variants conferred nearly 2-fold increased progression-free survival times. The current study provides evidence that genetic variations within the PI3K/PTEN/AKT/mTOR signaling pathway are associated with variation in clinical outcomes of NSCLC patients. With further validation, our findings may provide additional biomarkers for customized treatment of platinum-based chemotherapy for NSCLC.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

Cellular responses to Cisplatin-induced DNA damage

Cisplatin is one of the most effective anticancer agents widely used in the treatment of solid tumors. It is generally considered as a cytotoxic drug which kills cancer cells by damaging DNA and inhibiting DNA synthesis. How cells respond to cisplatin-induced DNA damage plays a critical role in deciding cisplatin sensitivity. Cisplatin-induced DNA damage activates various signaling pathways to prevent or promote cell death. This paper summarizes our current understandings regarding the mechanisms by which cisplatin induces cell death and the bases of cisplatin resistance. We have discussed various steps, including the entry of cisplatin inside cells, DNA repair, drug detoxification, DNA damage response, and regulation of cisplatin-induced apoptosis by protein kinases. An understanding of how various signaling pathways regulate cisplatin-induced cell death should aid in the development of more effective therapeutic strategies for the treatment of cancer.

MK-2206, an allosteric Akt inhibitor, enhances antitumor efficacy by standard chemotherapeutic agents or molecular targeted drugs in vitro and in vivo

The serine/threonine kinase Akt lies at a critical signaling node downstream of phosphatidylinositol-3-kinase and is important in promoting cell survival and inhibiting apoptosis. An Akt inhibitor may be particularly useful for cancers in which increased Akt signaling is associated with reduced sensitivity to cytotoxic agents or receptor tyrosine kinase inhibitors. We evaluated the effect of a novel allosteric Akt inhibitor, MK-2206, in combination with several anticancer agents. In vitro, MK-2206 synergistically inhibited cell proliferation of human cancer cell lines in combination with molecular targeted agents such as erlotinib (an epidermal growth factor receptor inhibitor) or lapatinib (a dual epidermal growth factor receptor/human epidermal growth factor receptor 2 inhibitor). Complementary inhibition of erlotinib-insensitive Akt phosphorylation by MK-2206 was one mechanism of synergism, and a synergistic effect was found even in erlotinib-insensitive cell lines. MK-2206 also showed synergistic responses in combination with cytotoxic agents such as topoisomerase inhibitors (doxorubicin, camptothecin), antimetabolites (gemcitabine, 5-fluorouracil), anti-microtubule agents (docetaxel), and DNA cross-linkers (carboplatin) in lung NCI-H460 or ovarian A2780 tumor cells. The synergy with docetaxel depended on the treatment sequence; a schedule of MK-2206 dosed before docetaxel was not effective. MK-2206 suppressed the Akt phosphorylation that is induced by carboplatin and gemcitabine. In vivo, MK-2206 in combination with these agents exerted significantly more potent tumor inhibitory activities than each agent in the monotherapy setting. These findings suggest that Akt inhibition may augment the efficacy of existing cancer therapeutics; thus, MK-2206 is a promising agent to treat cancer patients who receive these cytotoxic and/or molecular targeted agents.

Resistance to platinum-based chemotherapy in lung cancer cell lines

PURPOSE

A series of six lung cancer cell lines of different cell origin (including small cell and mesothelioma) were characterized immunohistochemically and the role of a series of protein candidates previously implicated in drug resistance were investigated.

METHODS

These include colony-forming and cell growth assays, immunohistochemistry, siRNA knockouts, real-time PCR and western blots.

RESULTS

No correlation was found with AKT, HO-1, HO-2, GRP78, 14-3-3zeta and ERCC1 levels and cisplatin nor oxaliplatin cytotoxicity, but an association was observed with levels of the enzyme, dihydrodiol dehydrogenase (DDH); an enzyme previously implicated in the development of platinum resistance. The relationship appeared to hold true for those cell lines derived from lung epithelial primary tumors but not for the neuroendocrine/small-cell and mesothelioma cell lines. siRNA knockouts to DDH-1 and DDH-2 were prepared with the cell line exhibiting the greatest resistance to cisplatin (A549) resulting in marked decreases in the DDH isoforms as assessed by real-time PCR, western blot and enzymatic activity. The DDH-1 knockout was far more sensitive to cisplatin than the DDH-2 knockout.

CONCLUSION

Thus, sensitivity to cisplatin appeared to be associated with DDH levels in epithelial lung cancer cell lines with the DDH-1 isoform producing the greatest effect. Results in keeping with transfection experiments with ovarian and other cell lines.

Inhibition of the insulin-like growth factor 1 receptor pathway enhances the antitumor effect of cisplatin in human malignant mesothelioma cell lines

Human malignant mesothelioma (HMM) is a fatal tumor and is poorly responsive to current therapeutic regimens. The insulin-like growth factor 1 receptor (IGF-1R) pathway is activated in HMM cell lines and tissues. Treatment with AG1024, an inhibitor of the IGF-1R pathway, significantly decreased cell proliferation and attenuated the phosphorylation of Akt and p44/42. In addition, it significantly enhanced the cytotoxic effects of cisplatin in HMM cell lines. This study supports the conjecture that inhibition of the IGF-1R pathway may be a useful target for reducing toxicity and alleviating chemoresistance to traditional anticancer drugs in HMM patients.

Phosphatidylinositol 3-kinase-Akt signaling in pulmonary carcinoid cells

BACKGROUND

In several types of cancer, upregulation of phosphatidylinositol 3-kinase (PI3K)-Akt signaling facilitates tumor cell growth and inhibits apoptosis. Previous reports demonstrated that this pathway promotes growth, survival, and chemotherapy resistance in non-small cell and small cell lung cancer cells. But the importance of PI3K-Akt signaling has not been explored in pulmonary carcinoids. In this study, our objective was to establish the role of the PI3K-Akt signal transduction pathway in pulmonary carcinoid cells.

STUDY DESIGN

Human pulmonary carcinoid NCI-H727 cells were treated with LY294002 (0 to 100 microM), a well-known PI3K inhibitor, or transfected with Akt1 small interfering RNA (75 nM). Cellular proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for up to 8 days. Western blot analysis was performed for expression of active, phosphorylated Akt (pAkt), total Akt, Akt1, and the neuroendocrine markers chromogranin A and achaete-scute complex-like1.

RESULTS

Treatment of NCI-H727 cells with LY294002 significantly reduced tumor cell growth (85.3%). Similarly, Akt1 small interfering RNA transfection led to diminished tumor cell proliferation (31.3%). A dose-dependent decrease in chromogranin A and achaete-scute complex-like1 production was observed with both PI3K inhibition and Akt1 RNA interference. Expression of Akt1 was reduced at all time points by transient Akt1 small interfering RNA transfection.

CONCLUSIONS

The PI3K-Akt pathway plays a role in both tumor cell growth and neuroendocrine hormone secretion in human pulmonary carcinoid cells. Inhibition of Akt1, PI3K-Akt signaling, or a downstream mediator of this pathway may provide therapeutic approaches for patients with pulmonary carcinoid tumors.

Conditional drug screening shows that mitotic inhibitors induce AKT/PKB-insensitive apoptosis

The phosphatidylinositol 3-kinase (PI3K)/AKT pathway is frequently upregulated in human cancer. Activation of this pathway has been reported to be associated with resistance to various chemotherapeutical agents. We here used a chemical biology/chemical informatic approach to identify apoptotic mechanisms that are insensitive to activation of the PI3K/AKT pathway. The National Cancer Institute (NCI) Mechanistic Set drug library was screened for agents that induce apoptosis in colon carcinoma cells expressing a constitutively active form of AKT1. The cytotoxicity screening data available as self-organized maps at the Developmental Therapeutics Program (DTP) of the NCI was then used to classify the identified compounds according to mechanism of action. The results showed that drugs that interfere with the mitotic process induce apoptosis which is comparatively insensitive to constitutive AKT1 activity. The conditional screening approach described here is expected to be useful for identifying relationships between the state of activation of signaling pathways and sensitivity to anticancer agents.

Perifosine inhibits growth of human experimental endometrial cancers by blockade of AKT phosphorylation

OBJECTIVE

Perifosine is an orally active alkylphospholipid analog, which has shown anti-tumor activity in a variety of cancers by inhibition of AKT phosphorylation. The objective of the current study was to evaluate its efficacy in in vitro models of human endometrial cancer.

STUDY DESIGN

The effect of 10microM and 40microM perifosine on AKT phophorylation in human endometrial cancer cell lines Ishikawa and HEC 1A was determined by Western blotting. To screen for a putative anti-tumor effect, HEC 1A and Ishikawa cells were incubated with increasing concentrations of perifosine for 24h, 48h and 72h and the number of viable cells was determined by crystal violet staining. Also the effect of a combined treatment with cisplatin and perifosine was investigated in Ishikawa cells. Flow cytometric analysis of DNA content was used to determine the effect of perifosine on the cell cycle distribution of HEC 1A and Ishikawa cells and to assess potential toxic side effects of perifosine on peripheral blood lymphocytes (PBL).

RESULTS

AKT phosphorylation was dose-dependently inhibited by perifosine. Concomitantly, perifosine displayed anti-tumor activity in both cell lines at concentrations that showed no effect on peripheral blood lymphocytes. Growth inhibitory effects became more pronounced with increasing treatment time. While IC 50 values at 24h were >40microM, IC 50 values after 48h were approximately 7microM in Ishikawa and 25microM in HEC 1A cells. After 72h, the IC 50 was below 1.25microM for Ishikawa and about 6microM for HEC 1A cells. Perifosine cotreatment substantially increased cytotoxic effects of cisplatin in human Ishikawa endometrial cancer cells. Of note, the anti-tumor activity of perifosine was not confined to a specific phase of the cell cycle.

CONCLUSIONS

The small molecule AKT inhibitor perifosine showed substantial anti-tumor activity in human endometrial cancer cell lines. Since these effects were increased with cisplatin, perifosine seems to be a good candidate for treatment combinations with classical cytostatic compounds. Thus, perifosine should be further evaluated in clinical studies in endometrial cancer.