Suppression of tumorigenicity and metastasis in B16F10 cells by PTEN/MMAC1/TEP1 gene

PTEN Expression Was Significantly Associated with PD-L1 Score but Not with EBV Infection in Gastric Cancer

Purpose

Gastric cancer (GC) remains a prevalent aggressive tumor with high morbidity and mortality globally. The identification of GC subtypes based on molecular features improved the prediction of prognosis and the selection of targeted therapies. PTEN is a characteristic tumor suppressor, while its association with different GC subtypes was unknown.

Patients and Methods

The cohort consisted of 248 patients diagnosed with gastric cancer who were hospitalized and received radical gastrectomy. In addition, PTEN gene expression matrix of STAD was retrieved from TCGA. The mRNA and protein levels of PTEN and PD-L1 were detected using qRT-PCR and IHC staining. Multivariate logistic regression and Kaplan–Meier analysis were used to examine the relationship between PTEN expression and clinical characteristics.

Results

In our study, PTEN was downregulated in gastric tumors both in mRNA and protein levels. Its inactivation was closely linked to higher histological grade (P = 0.005), neural invasion (P = 0.012), depth of invasion (P = 0.021), lymph metastasis (P = 0.026), and TNM stage (P = 0.001) of GC in the present study. Moreover, according to the molecular subtypes, high PTEN expression was related to high TPS score of PD-L1 positively (P = 0.010) but was not associated with MSI and EBV infection. Further, TCGA data validated that PTEN was indeed correlated with histological grade and invasion depth and positively related to PD-L1 expression (R = 0.29, adjusted P < 0.001).

Conclusion

The above results suggested that PTEN expression was a useful marker in gastric carcinogenesis and progression and in the selection of immunotherapy-based treatments for GC patients.

MetastaSite: Predicting metastasis to different sites using deep learning with gene expression data

Deep learning has massive potential in predicting phenotype from different omics profiles. However, deep neural networks are viewed as black boxes, providing predictions without explanation. Therefore, the requirements for these models to become interpretable are increasing, especially in the medical field. Here we propose a computational framework that takes the gene expression profile of any primary cancer sample and predicts whether patients' samples are primary (localized) or metastasized to the brain, bone, lung, or liver based on deep learning architecture. Specifically, we first constructed an AutoEncoder framework to learn the non-linear relationship between genes, and then DeepLIFT was applied to calculate genes' importance scores. Next, to mine the top essential genes that can distinguish the primary and metastasized tumors, we iteratively added ten top-ranked genes based upon their importance score to train a DNN model. Then we trained a final multi-class DNN that uses the output from the previous part as an input and predicts whether samples are primary or metastasized to the brain, bone, lung, or liver. The prediction performances ranged from AUC of 0.93-0.82. We further designed the model's workflow to provide a second functionality beyond metastasis site prediction, i.e., to identify the biological functions that the DL model uses to perform the prediction. To our knowledge, this is the first multi-class DNN model developed for the generic prediction of metastasis to various sites.

LncRNA CASC9 promotes proliferation, migration and inhibits apoptosis of hepatocellular carcinoma cells by down-regulating miR-424-5p

INTRODUCTION AND OBJECTIVES

CASC9 and miR-424-5p are closely related with hepatocellular carcinoma (HCC) progression. This study aimed to evaluate the effect of CASC9 involved with miR-424-5p on the development of HCC.

MATERIALS AND METHODS

qRT-PCR was performed to determine the mRNA expressions of CASC9 and miR-424-5p in HCC tissues/cells and adjacent normal tissues/human hepatic epithelial cells, and to analyze the relationship of CASC9 with the clinico-pathological characteristics and prognosis of HCC patients. Then, cell proliferation was measured by CCK-8 and¹ clone formation assays. Apoptosis of HCC cells was measured by flow cytometry. Besides, cell migration and invasion were determined by scratch wound-healing and Transwell assays, respectively. DIANA-LncBase V2 and dual luciferase reporter gene assay were used to verify the targeted relationship between CASC9 and miR-424-5p. Bcl-2, Bax and cleaved caspase-3 expressions were detected by Western blot.

RESULTS

Higher expression of CASC9 was observed in HCC tissues/ cells than in adjacent normal tissues/ human hepatic epithelial cells, and was closely linked to poor prognosis of HCC, tumor size, TNM stage, differentiation degree, lymph node metastasis and alpha-fetoprotein (AFP). Down-regulation of CASC9 decreased the proliferation, invasion and migration of HCC cells while enhancing apoptosis. Besides, CASC9 was negatively correlated with miR-424-5p. MiR-424-5p inhibitor enhanced cell proliferation, invasion and migration while decreasing apoptosis. Interestingly, siRNA-CASC9 partially offset the effects of miR-424-5p inhibitor on HCC cells.

CONCLUSION

CASC9 promoted proliferation, invasion and migration and inhibited apoptosis in HCC cells by inhibiting miR-424-5p.

Upregulation of DJ-1 expression in melanoma regulates PTEN/AKT pathway for cell survival and migration

Cutaneous melanoma is known to be one of the most dangerous skin cancers because of its metastatic functions. Today, it is essential to investigate specific biomarkers for the target treatment in many diseases including cancers. DJ-1 protein, also known as Parkinson disease 7, has various functions associated with cancer progression including cell survival and migration. Phosphatase and tensin homolog (PTEN) is a tumor suppressor that regulates the PI3K/AKT signaling pathway and its mutations have been reported to frequently occur in many cancers such as thyroid, breast and skin. Recently, DJ-1 has been identified as a negative regulator of PTEN in many human cancer cells. However, the impacts and relationship of DJ-1 and PTEN have not been studied yet in melanoma. To confirm the expression of DJ-1 and PTEN in melanoma compared to normal skin tissues and find out functions of DJ-1 in melanoma cells, Western blot analysis and immunohistochemical staining were used. Transfection of G361 cells with DJ-1-specific small interfering RNA was performed to figure out the roles of DJ-1 and the relationship between DJ-1 and PTEN in melanoma cells. In our study, the DJ-1 protein was significantly increased with loss of PTEN protein in melanoma compared to that in normal skin. Inhibition of DJ-1 in G361 cells induced apoptosis, and suppressed cell survival and migration. Furthermore, suppression of DJ-1 in G361 cells increased the expression of cleaved caspase-3, cleaved PARP, Bax, p53, and Daxx as well as PTEN, while it decreased expression of survivin, caspase-3, and PARP. Also, downregulated DJ-1 inhibited phosphorylation of AKT in G361 cells. Collectively, DJ-1 overexpression could affect the proliferative and invasive capabilities of melanoma cells via regulating the PTEN/AKT pathway and apoptosis-related proteins. This study suggests that DJ-1 may be a potential target for the treatment of melanoma.

Unravelling the anticancer efficacy of 10-oxo-7-epidocetaxel: in vitro and in vivo results

PURPOSE

To prepare 7-epidocetaxel (7ED) and 10-oxo-7-epidocetaxel (10-O-7ED) formulations as like marketed Taxotere® (TXT) injection and to screen them for in vitro and in vivo anticancer efficacy including their in vivo toxicity behavior.

METHODS

The 7ED and 10-O-7ED formulations were screened for in vitro anti-proliferative, anti-metastatic and cell cycle arresting behaviors. Further, in vivo acute toxicity of TXT injection containing 10% of 7ED and 10-O-7ED separately and the therapeutic study of 10-O-7ED alone were studied in B16F10 experimental metastasis mouse model.

RESULTS

10-O-7ED caused significantly higher cytotoxicity after 48 and 72 h than 22 h study. 10-O-7ED showed significantly increased in vitro anti-metastatic activity than TXT. The TXT caused more arrest of cells at S phase, whereas 10-O-7ED arrested more at G2-M phase and vice versa at higher concentration. In vivo acute toxicity study revealed better therapeutic effect with reduced toxicity of TXT containing 10% 10-O-7ED than TXT alone. Similarly, the therapeutic study revealed significantly less number of surface metastatic nodules formation with 10-O-7ED treated group (107 ± 49) (***p < .0001) than control group (348 ± 56). Also, the control group showed significant weight loss at the end (20th day) of the experiment (*p < .05, p = .041) than 10-O-7ED treated group which showed about 4% increased mean group weight.

CONCLUSION

Our study revealed the significantly higher in vivo anti-metastatic behavior, with no toxicity, of 10-O-7ED. However, it is a preliminary observation being noticed but further investigations are needed to address the potential of 10-O-7ED in cancer treatment with mechanisms behind the improved therapeutic efficacy with no toxicity.

Concomitant modulation of PTEN and Livin in gastric cancer treatment

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and Livin are important in the development of gastric cancer (GC). PTEN and Livin are involved in the regulation of tumor cell proliferation, migration and apoptosis. The modulation of PTEN or Livin has been investigated extensively in various cancer models. However, no studies have been performed to evaluate the combined effect of concurrently modulating these two genes on the development of GC. In the present study, the BGC823 human gastric carcinoma cell line was transfected with a dual gene modified vector (pCL-neo-PTEN-siLivin) in parallel with single gene modified vectors (pCL‑neo‑PTEN or pRNAT‑U6.1‑siLivin), and an empty control vector. Dual gene modulation (pCL‑neo‑PTEN‑siLivin) had a more marked effect on the inhibition of cell proliferation, induction of apoptosis, and reduction of cell penetration in Matrigel, compared with either single gene alone or empty vector transfection. In a xenograft nude mouse model, the inoculation of pCL‑neo‑PTEN‑siLivin‑transfected BGC823 cells led to a markedly reduced tumor burden, compared with that in all other inoculation groups. In conclusion, the overexpression of PTEN concomitant with Livin gene silencing was confirmed as a feasible and effective in vitro and in vivo gene modulation method, which may represent a potential therapeutic strategy for the treatment of GC.

LDOC1 regulates Wnt5a expression and osteosarcoma cell metastasis and is correlated with the survival of osteosarcoma patients

Osteosarcomas are common bone malignancies in children and adolescents. LDOC1 (leucine zipper, down-regulated in cancer 1), a tumor suppressor, is down-regulated in many cancers. In this study, we investigated the role of LDOC1 in tumor metastasis and its prognostic significance in osteosarcomas. We established osteosarcoma cells stably expressing LDOC1, driven by an HIV-based lentiviral system. We investigated the impact of LDOC1 on migration and invasion abilities in these cells using a transwell assay. LDOC1-associated changes in expression of metastasis-promoting genes were analyzed with a quantitative real-time polymerase chain reaction primer array. A xenograft tumor model (n = 7 mice/group) was used to assess the effect of LDOC1 on osteosarcoma metastasis in vivo. The overall survival and disease-free survival of osteosarcoma patients (n = 74) were analyzed retrospectively based on immunohistochemical analysis of LDOC1 levels in tumors and Kaplan-Meier analysis. LDOC1-expressing osteosarcoma cells displayed decreased migration and invasion in vitro. The quantitative real-time polymerase chain reaction primer array data showed that increased LDOC1 expression up-regulated many metastasis-suppressor genes. In the xenograft model, micro-computed tomography imaging data indicated that increased LDOC1 expression is associated with weaker lung metastasis ability. The Wnt5a signaling pathway promotes osteosarcoma metastasis; LDOC1 expression decreased Wnt5a levels in osteosarcoma cells. Kaplan-Meier analysis showed that higher LDOC1 expression was associated with improved osteosarcoma patient overall survival and disease free survival (p = 0.022). Our data show that LDOC1 is a tumor suppressor in osteosarcoma, and that it regulates metastasis of osteosarcoma cells. Furthermore, LDOC1 might be a valuable prognostic marker in osteosarcomas.

PERK Is a Haploinsufficient Tumor Suppressor: Gene Dose Determines Tumor-Suppressive Versus Tumor Promoting Properties of PERK in Melanoma

The unfolded protein response (UPR) regulates cell fate following exposure of cells to endoplasmic reticulum stresses. PERK, a UPR protein kinase, regulates protein synthesis and while linked with cell survival, exhibits activities associated with both tumor progression and tumor suppression. For example, while cells lacking PERK are sensitive to UPR-dependent cell death, acute activation of PERK triggers both apoptosis and cell cycle arrest, which would be expected to contribute tumor suppressive activity. We have evaluated these activities in the BRAF-dependent melanoma and provide evidence revealing a complex role for PERK in melanoma where a 50% reduction is permissive for Braf^V600E-dependent transformation, while complete inhibition is tumor suppressive. Consistently, PERK mutants identified in human melanoma are hypomorphic with dominant inhibitory function. Strikingly, we demonstrate that small molecule PERK inhibitors exhibit single agent efficacy against Braf^V600E-dependent tumors highlighting the clinical value of targeting PERK.

PERK is critical for progression of specific cancers and has provided stimulus for the generation of small molecule PERK inhibitors. Paradoxically, the anti-proliferative and pro-death functions of PERK have potential tumor suppressive qualities. We demonstrate that PERK can function as either a tumor suppressor or a pro-adaptive tumor promoter and the nature of its function is determined by gene dose. Preclinical studies suggest a therapeutic threshold exists for PERK inhibitors.

PTEN Promoter Methylation and Protein Expression in Normal Early Placentas and Hydatidiform Moles

OBJECTIVE

To investigate the relationship between PTEN promoter methylation and protein expression, and the possible involvement of the PTEN gene in development of gestational trophoblasts and the pathogenesis of hydatidiform moles.

METHODS

DNA was extracted from choria of normal early placentas, partial hydatidiform moles, complete hydatidiform moles, and invasive moles, and overdigested by methylation-sensitive endonuclease HpaII. The PTEN promoter was amplificated by polymerase chain reaction. PTEN protein expression was detected by immunohistochemistry.

RESULTS

In partial and complete hydatidiform moles, the PTEN promoter methylation rate was significantly higher than in early placentas (72%, 59.4%, 14.3%; P = .000, .002, respectively), and the PTEN protein expression rate was significantly lower than in early placentas (9.1%, 4.5%, 90.5%; P = .000, .000, respectively). However, partial hydatidiform moles, complete hydatidiform moles, and invasive moles were not significant different in terms of PTEN promoter methylation and protein expression.

CONCLUSIONS

These findings suggest that the regulation of PTEN expression may play an important role in the development of the early gestational trophoblast and in the pathogenesis of hydatidiform mole, but not in its malignant transformation.

Directed migration of cancer cells guided by the graded texture of the underlying matrix

Living cells and the extracellular matrix (ECM) can exhibit complex interactions that define key developmental, physiological and pathological processes. Here, we report a new type of directed migration-which we term 'topotaxis'-guided by the gradient of the nanoscale topographic features in the cells' ECM environment. We show that the direction of topotaxis is reflective of the effective cell stiffness, and that it depends on the balance of the ECM-triggered signalling pathways PI(3)K-Akt and ROCK-MLCK. In melanoma cancer cells, this balance can be altered by different ECM inputs, pharmacological perturbations or genetic alterations, particularly a loss of PTEN in aggressive melanoma cells. We conclude that topotaxis is a product of the material properties of cells and the surrounding ECM, and propose that the invasive capacity of many cancers may depend broadly on topotactic responses, providing a potentially attractive mechanism for controlling invasive and metastatic behaviour.

Synergistic tumor suppression by adenovirus-mediated ING4/PTEN double gene therapy for gastric cancer

Both inhibitor of growth 4 (ING4) and phosphatase and tensin homolog (PTEN) have been shown to be strong candidate tumor suppressors. However, the combined efficacy of ING4 and PTEN for human gastric cancer remains to be determined. In this report, we constructed a multiple promoter expression cassette-based recombinant adenovirus coexpressing ING4 and PTEN (AdVING4/PTEN), assessed the combined effects of AdVING4/PTEN on gastric cancer using wild-type p53 AGS and SNU-1 human gastric cancer cell lines, and elucidated its underlying mechanisms. We found that AdVING4/PTEN-induced synergistic growth inhibition and apoptosis in vitro AGS or SNU-1 tumor cells and in vivo AGS xenografted tumors subcutaneously inoculated in athymic BALB/c nude mice. Mechanistically, AdVING4/PTEN exhibited an enhanced effect on upregulation of p53, Ac-p53 (K382), P21, Bax, PUMA, Noxa, cleaved Caspase-9, cleaved Caspase-3 and cleaved PARP as well as downregulation of Bcl-2 in vitro and in vivo. In addition, AdVING4/PTEN synergistically downregulated tumor vessel CD34 expression and reduced microvessel density, and additively inhibited vascular endothelial growth factor (VEGF) expression in vivo. The synergistic tumor suppression elicited by AdVING4/PTEN was closely associated with the synergistic induction of apoptosis possibly via enhancement of endogenous p53 responses through cooperatively facilitating p53's stability and acetylation, and the synergistic inhibition of tumor angiogenesis probably via overlapping reduction of VEGF through cooperatively downregulating hypoxia inducible factor-1α's level and transcription activity. Thus, our results indicate that cancer gene therapy combining ING4 and PTEN may constitute a novel and effective therapeutic modality for human gastric cancer and other cancers.

Phosphatase and Tensin Homolog (PTEN) Represses Colon Cancer Progression through Inhibiting Paxillin Transcription via PI3K/AKT/NF-κB Pathway

The tumor suppressor gene phosphatase and tensin homolog (PTEN) is frequently mutated in colon cancer. However, the potential contribution of loss of PTEN to colon cancer progression remains unclear. In this study, we demonstrated that PTEN overexpression or knockdown in Lovo colon cancer cells decreased or increased paxillin expression, respectively. Moreover, paxillin reversed PTEN-mediated inhibition of Lovo cell invasion and migration. Overexpression of PTEN in an orthotropic colon cancer nude mice model inhibited tumor formation and progression. In addition, PTEN protein level was negatively correlated with that of paxillin in human colon cancer tissues. Mechanistically, we identified three NF-κB binding sites on paxillin promoter and confirmed that paxillin was a direct transcriptional target of NF-κB. Our findings reveal a novel mechanism by which PTEN inhibits the progression of colon cancer by inhibiting paxillin expression downstream of PI3K/AKT/NF-κB pathway. Thereby, PTEN/PI3K/AKT/NF-κB/paxillin signaling cascade is an attractive therapeutic target for colon cancer progression.

Roles of PTEN (Phosphatase and Tensin Homolog) in gastric cancer development and progression

Gastric cancer is highly invasive, aggressively malignant, and amongst the most prevalent of all forms of cancer. Despite improved management strategies, early stage diagnosis of gastric cancer and accurate prognostic assessment is still lacking. Several recent reports have indicated that the pathogenesis of gastric cancer involves complex molecular mechanisms and multiple genetic and epigenetic alterations in oncogenes and tumor suppressor genes. Functional inactivation of the tumor suppressor protein PTEN (Phosphatase and Tensin Homolog) has been detected in multiple cases of gastric cancer, and already shown to be closely linked to the development, progression and prognosis of the disease. Inactivation of PTEN can be attributed to gene mutation, loss of heterozygosity, promoter hypermethylation, microRNA- mediated regulation of gene expression, and post-translational phosphorylation. PTEN is also involved in mechanisms regulating tumor resistance to chemotherapy. This review provides a comprehensive analysis of PTEN and its roles in gastric cancer, and emphasizes its potential benefits in early diagnosis and gene therapy-based treatment strategies.

The hedgehog receptor patched1 in T cells is dispensable for adaptive immunity in mice

Hedgehog (Hh) signaling modulates T cell development and function but its exact role remains a matter of debate. To further address this issue we made use of conditional knock-out mice in which the Hh receptor Patched1 (Ptch) is inactivated in the T cell lineage. Thymocyte development was moderately compromised by the deletion of Ptch as characterized by reduced numbers of CD4 and CD8 single-positive cells. In contrast, peripheral T cells were not affected. Proliferation and IFNγ secretion by Ptch-deficient T cells were indistinguishable from controls irrespectively of whether we used strong or suboptimal conditions for stimulation. Analysis of CTL and T_reg cell functions did not reveal any differences between both genotypes, and T cell apoptosis induced by glucocorticoids or γ-irradiation was also similar. Surprisingly, absence of Ptch did not lead to an activation of canonic Hh signaling in peripheral T cells as indicated by unaltered expression levels of Gli1 and Gli2. To test whether we could uncover any role of Ptch in T cells in vivo we subjected the mutant mice to three different disease models, namely allogeneic bone marrow transplantation mimicking graft-versus-host disease, allergic airway inflammation as a model of asthma and growth of adoptively transferred melanoma cells as a means to test tumor surveillance by the immune system. Nonetheless, we were neither able to demonstrate any difference in the disease courses nor in any pathogenic parameter in these three models of adaptive immunity. We therefore conclude that the Hh receptor Ptch is dispensable for T cell function in vitro as well as in vivo.

Enhanced tumor suppression by adenoviral PTEN gene therapy combined with cisplatin chemotherapy in small-cell lung cancer

DNA-damaging anticancer drug cisplatin (cis-diamminedichloroplatinum) (DDP)-based chemotherapy is the mainstay and standard treatment for small-cell lung cancer (SCLC). However, frequent relapse and chemoresistance of SCLC remains a significant therapeutic hurdle. Tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) as a negative regulator of phosphoinositide 3-kinase/AKT survival pathway exhibits strong tumor-suppressive activities. A combination of chemotherapy and gene therapy (chemogene therapy) is a promising practice in cancer therapy. In this report, we examined the combined antitumor effect of adenovirus-mediated PTEN (AdVPTEN) gene therapy and DDP chemotherapy on PTEN-null NCI-H446 human SCLC cells in vitro and in vivo in athymic BALB/c nude mice. We demonstrated that AdVPTEN plus DDP enhanced growth suppression, cell-cycle G1 phase arrest and apoptosis in in vitro NCI-H446 tumor cells and in vivo NCI-H446 xenografted tumors subcutaneously inoculated in nude mice. Mechanistically, AdVPTEN plus DDP exerted an overlapping effect on upregulation of P53, P21, P27, Bax and Cleaved Caspase-3 as well as downregulation of Bcl-2 and survivin in in vitro and in vivo NCI-H446 tumor cells. Moreover, AdVPTEN plus DDP additively reduced tumor vessel CD34 expression and microvessel density in vivo. The enhanced therapeutic efficacy elicited by AdVPTEN plus DDP was closely associated with additive induction of G1 phase arrest and apoptosis via substantially modulating cell-cycle regulation molecules and activating intrinsic apoptotic pathway through P53 restoration, and overlapping inhibition of tumor angiogenesis. Thus, our results indicated that AdVPTEN combined with DDP may be a novel and effective chemogene therapy modality for human SCLC.

PTEN/MAPK pathways play a key role in platelet-activating factor-induced experimental pulmonary tumor metastasis

In this study, we investigated the role of PTEN (phosphatase and tensin homolog deleted on chromosome 10) in a platelet-activating factor (PAF)-induced experimental pulmonary tumor metastasis model. An adenovirus carrying PTEN cDNA (Ad-PTEN) reversed PAF-induced increase in phosphorylation of AKT as well as pulmonary metastasis of B16F10. PAF-induced pulmonary metastasis was inhibited by MAPK inhibitors, but not by PI3K inhibitor. Ad-PTEN abrogated PAF-induced phosphorylation of MAPKs. These data indicate PTEN/MAPK pathways play a key role in PAF-induced tumor metastasis.

Genetic alterations of PTEN in human melanoma

The PTEN gene is one of the most frequently inactivated tumor suppressor genes in sporadic cancers. Inactivating mutations and deletions of the PTEN gene are found in many types of cancers, including melanoma. However, the exact frequency of PTEN alteration in melanoma is unknown. In this study, we comprehensively reviewed 16 studies on PTEN genetic changes in melanoma cell lines and tumor biopsies. To date, 76 PTEN alterations have been reported in melanoma cell lines and 38 PTEN alterations in melanoma biopsies. The rate of PTEN alterations in melanoma cell lines, primary melanoma, and metastatic melanoma is 27.6, 7.3, and 15.2%, respectively. Three mutations were found in both melanoma cell lines and biopsies. These mutations are scattered throughout the gene, with the exception of exon 9. A mutational hot spot is found in exon 5, which encodes the phosphatase activity domain. Evidence is also presented to suggest that numerous homozygous deletions and missense variants exist in the PTEN transcript. Studying PTEN functions and implications of its mutations and other genes could provide insights into the precise nature of PTEN function in melanoma and additional targets for new therapeutic approaches.

Growth suppression of human lung cancer cells and implanted tumors by adenovirus-mediated transfer of the PTEN gene

This study examined the effects of a recombinant adenovirus Ad-PTEN-EGFP on the proliferation of A549 cells, a human lung carcinoma cell line, in vitro and on the growth of the implanted tumors in the nude mice in vivo, explored the underlying mechanisms and evaluated the in vitro transfection efficiency of Ad-PTEN-EGFP into A549 cells. The expression of Ad-PTEN-EGFP in the A549 cells was determined. The proliferation and the apoptosis rates of the A549 cells with Ad-PTEN-EGFP transfection or not was detected by MTT and flow cytometry. Ad-PTEN-EGFP at different doses was injected intratumorally to the tumor-bearing mice induced by the A549 cells. Tumor sizes were measured on an alternate day. After all the mice were sacrificed, the implanted tumors were removed for routine histological examination, weight test, HE staining and immunohistochemical staining. The expressions of Bax, P16 and P53 in the tumor tissues and those of caspase-3, CD34 and VEGF in the mouse sera were detected. Tumor cell apoptosis was measured by TUNEL method. The results showed that the vitality of the A549 cells after transfection with Ad-PTEN-EGFP declined. The expression of green fluorescent protein was observed under fluorescent microscope. The transfection rate was in excess of 50%. The mRNA and protein expression of PTEN in the transfected cells was confirmed. The proliferation rate of the transfected cells was significantly decreased when compared with that of the non-transfected cells (P<0.05). The number of the apoptosis cells was increased in the transfected cells (P<0.05). The models of implanted tumors were successfully established by injection of the A549 cells in the flank of Balb/c nude mice. Administration of Ad-PTEN-EGFP to the tumor-bearing nude mice resulted in a suppression of tumor growth. There were statistically significant differences in the tumor weight and tumor volume between the Ad-PTEN-EGFP-treated group and the control groups (P<0.05). In contrast to those in the control groups, tumor tissues in the Ad-PTEN-EGFP-treated group were shown to have typical extensive vacuolar degeneration and massive hemorrhagic necrosis. Apoptotic bodies were also observed in the tumor cells. The expressions of Bax, caspase-3 and P16 were increased (P<0.05) while those of CD34, VEGF and P53 decreased (P<0.05) in the Ad-PTEN-EGFP-treated group. It is concluded that Ad-PTEN-EGFP could induce the apoptosis of the A549 cells and inhibit their proliferation. And it could also substantially suppress the tumor growth in the tumor-bearing nude mice and induce apoptosis of the tumor cells as well. These findings carry significant implications for adenovirus vector-based PTEN gene therapies for lung cancers.

Molecular pathogenesis of cutaneous melanocytic neoplasms

Melanoma is the deadliest form of skin cancer without an effective treatment. An understanding of the genetic basis of melanoma has recently shed light on some of the mechanisms of melanomagenesis. This review explores the major genes involved in familial and sporadic cutaneous melanoma with an emphasis on CDKN2A, CDK4, MC1R, and MAPK pathway targets (e.g., RAS and BRAF), apoptosis regulators (e.g., BCL-2, AKT, and APAF-1), and the tumor-suppressor genes TP53 and PTEN. New directions for therapeutics based on our current knowledge of the genes implicated in melanoma are also discussed.

Pten deficiency in melanocytes results in resistance to hair graying and susceptibility to carcinogen-induced melanomagenesis

Phosphate and tensin homologue deleted on chromosome 10 (PTEN) is a tumor suppressor gene inactivated in numerous sporadic cancers, including melanomas. To analyze Pten functions in melanocytes, we used the Cre-loxP system to delete Pten specifically in murine pigment-producing cells and generated DctCrePten(flox/flox) mice. Half of DctCrePten(flox/flox) mice died shortly after birth with enlargements of the cerebral cortex and hippocampus. Melanocytes were increased in the dermis of perinatal DctCrePten(flox/flox) mice. When the mutants were subjected to repeated depilations, melanocyte stem cells in the bulge of the hair follicle resisted exhaustion and the mice were protected against hair graying. Although spontaneous melanomas did not form in DctCrePten(flox/flox) mice, large nevi and melanomas developed after carcinogen exposure. DctCrePten(flox/flox) melanocytes were increased in size and exhibited heightened activation of Akt and extracellular signal-regulated kinases, increased expression of Bcl-2, and decreased expression of p27(Kip1). Our results show that Pten is important for the maintenance of melanocyte stem cells and the suppression of melanomagenesis.

Combination of all-trans retinoic acid and interferon-gamma upregulated p27(kip1) and down regulated CDK2 to cause cell cycle arrest leading to differentiation and apoptosis in human glioblastoma LN18 (PTEN-proficient) and U87MG (PTEN-deficient) cells

PURPOSE

Deletion or mutation of phosphatase and tensin homolog located on chromosome ten (PTEN) occurs in as high as 80% glioblastoma. All-trans retinoic acid (ATRA) induces differentiation in cancer cells. Interferon-gamma (IFN-gamma) induces apoptosis in many cancers including glioblastoma. We used the combination of ATRA and IFN-gamma to control growth of human glioblastoma LN18 (PTEN-proficient) and U87MG (PTEN-deficient) cells and explored any advantage of having PTEN in the cells.

METHODS

LN18 and U87MG cells were treated with ATRA (1 microM) for 7 days and then IFN-gamma (5 ng/ml) for 1 day. Methylene blue staining indicated astrocytic differentiation. Wright staining and ApopTag assay showed characteristic features of apoptosis. Western blotting demonstrated the levels of specific proteins.

RESULTS

ATRA and IFN-gamma alone and in combination could induce apoptosis in LN18 cells; while ATRA alone induced differentiation only, IFN-gamma alone induced apoptosis, and ATRA plus IFN-gamma increased apoptosis in U87MG cells. The variation in induction of apoptosis by ATRA alone might be attributed to difference in PTEN expression in the two cell lines. Compared with control cells, IFN-gamma alone and ATRA plus IFN-gamma increased PTEN expression in LN18 cells while there was no PTEN expression or induction in U87MG cells after treatments with ATRA alone and ATRA plus IFN-gamma. Apoptosis in both cell lines was associated with increases in Bax:Bcl-2 ratio, mitochondrial release of cytochrome c into the cytosol, and calpain and caspase-3 activities. Treatments elevated p27(kip1) and decreased CDK2 levels in both cell lines, indicating cell cycle arrest at G(1)/S phase.

CONCLUSIONS

The combination of ATRA and IFN-gamma could control the growth of both PTEN-proficient and PTEN-deficient glioblastoma cells by arresting cell division and inducing differentiation and apoptosis. Thus, our study indicated that the growth of both PTEN-proficient and PTEN-deficient glioblastoma cells could effectively be controlled by treatment with the combination of ATRA and IFN-gamma.

PCR-SSCP-DNA sequencing method in detecting PTEN gene mutation and its significance in human gastric cancer

AIM: To discuss the possible effect of PTEN gene mutations on occurrence and development of gastric cancer.

METHODS: Fifty-three gastric cancer specimens were selected to probe PTEN gene mutations in genome of gastric cancer and paracancerous tissues using PCR-SSCP-DNA sequencing method based on microdissection and to observe the protein expression by immunohistochemistry technique.

RESULTS: PCR-SSCP-DNA sequencing indicated that 4 kinds of mutation sites were found in 5 of 53 gastric cancer specimens. One kind of mutation was found in exons. AA-TCC mutation was located at 40bp upstream of 3’ lateral exon 7 (115946 AA-TCC). Such mutations led to terminator formation in the 297th codon of the PTEN gene. The other 3 kinds of mutation were found in introns, including a G-C point mutation at 91 bp upstream of 5’ lateral exon 5(90896 G-C), a T-G point mutation at 24 bp upstream of 5’ lateral exon 5 (90963 T-G), and a single base A mutation at 7 bp upstream of 5’ lateral exon 5 (90980 A del). The PTEN protein expression in gastric cancer and paracancerous tissues detected using immunohistochemistry technique indicated that the total positive rate of PTEN protein expression was 66% in gastric cancer tissue, which was significantly lower than that (100%) in paracancerous tissues (P < 0.005).

CONCLUSION: PTEN gene mutation and expression may play an important role in the occurrence and development of gastric cancer.

Understanding signaling cascades in melanoma

Understanding regulatory pathways involved in melanoma development and progression has advanced significantly in recent years. It is now appreciated that melanoma is the result of complex changes in multiple signaling pathways that affect growth control, metabolism, motility and the ability to escape cell death programs. Here we review the major signaling pathways currently known to be deregulated in melanoma with an implication to its development and progression. Among these pathways are Ras, B-Raf, MEK, PTEN, phosphatidylinositol-3 kinase (PI3Ks) and Akt which are constitutively activated in a significant number of melanoma tumors, in most cases due to genomic change. Other pathways discussed in this review include the [Janus kinase/signal transducer and activator of transcription (JAK/STAT), transforming growth factor-beta pathways which are also activated in melanoma, although the underlying mechanism is not yet clear. As a paradigm for remodeled signaling pathways, melanoma also offers a unique opportunity for targeted drug development.

The RTK/RAS/BRAF/PI3K pathways in melanoma: biology, small molecule inhibitors, and potential applications

The discovery of mutations in the BRAF signaling molecule in a large proportion of cutaneous melanomas immediately suggested the prospect of effective therapies for this disease. The most appealing initial target has been BRAF itself, as most mutations involve a single residue in the kinase domain of the protein. But the identification of the high mutation rate in this signaling intermediate also suggests that other molecules up- and downstream of BRAF might be productively targeted. Indeed, several receptor tyrosine kinases, as well as RAS, are mutated in a small number of melanoma cases. Moreover, genetic alterations in the phosphotidylinositol-3-kinase (PI3K) pathway, especially in PTEN, suggest that this route also poses opportunities for therapeutic exploitation. We will review here the genetic evidence suggesting the utility of targets on these pathways. We will also summarize the recent clinical data that have accumulated from initial trials designed to test BRAF inhibition and targeting of other molecules. Finally, we provide an overview of molecules entering the clinic and soon to be tested in clinical studies, as well as strategies for their employment as monotherapy and in combinations.

Genetics of melanoma tumorigenesis

Melanoma therapy is moving away from combinatorial approaches and towards newer targeted strategies. With the identification of mutations in various RAS pathway genes, there are now tremendous opportunities to bring inhibitors of RAS signalling to the clinical arena.

Combination of all-trans retinoic acid and interferon-gamma suppressed PI3K/Akt survival pathway in glioblastoma T98G cells whereas NF-kappaB survival signaling in glioblastoma U87MG cells for induction of apoptosis

Phosphatase and tension homolog located on chromosome ten (PTEN) is a tumor suppressor as it negatively regulates activation of Akt. Mutation or deletion of PTEN has been found in as high as 80% of glioblastomas, which harbor aberrant cell signaling passing through the phosphatidylinositol-3-kinase (PI3K) and Akt (PI3K/Akt) survival pathway. Glioblastoma cells without functional PTEN are not easily amenable to apoptosis. We investigated the possibility of modulation of signal transduction pathways for induction of apoptosis in human glioblastoma T98G (PTEN-harboring) and U87MG (PTEN-deficient) cell lines after treatment with the combination of all-trans retinoic acid (ATRA) and interferon-gamma (IFN-gamma). Treatment with ATRA plus IFN-gamma stimulated PTEN expression and suppressed Akt activation in T98G cells, whereas no PTEN expression but Akt activation in U87MG cells under the same conditions. Pretreatment of U87MG cells with the PI3K inhibitor LY294002 could prevent Akt activation. Interestingly, ATRA plus IFN-gamma could significantly decrease cell viability and increase morphological features of apoptosis in both cell lines. Combination of ATRA and IFN-gamma showed more efficacy than IFN-gamma alone in causing apoptosis that occurred due to increases in Bax:Bcl-2 ratio, mitochondrial release of cytochrome c, and caspase-3 activity. Luciferase reporter gene assay showed that combination of ATRA and IFN-gamma significantly down regulated transcriptional activity of the nuclear factor kappa B (NF-kappaB), a survival signaling factor, in U87MG cells. Thus, combination of ATRA and IFN-gamma caused significant amounts of apoptosis in T98G cells due to suppression of the PI3K/Akt survival pathway while the same treatment caused apoptosis in U87MG cells due to down regulation of the NF-kappaB activity. Therefore, the combination of ATRA and IFN-gamma could modulate different survival signal transduction pathways for induction of apoptosis and should be considered as an effective therapeutic strategy for controlling the growth of both PTEN-harboring and PTEN-deficient glioblastomas.

Peroxisome proliferator-activated receptor gamma and retinoic acid receptor synergistically up-regulate the tumor suppressor PTEN in human promyeloid leukemia cells

Peroxisome proliferator-activated receptor gamma (PPARgamma) and retinoic acid receptors (RARs) have been a focus in chemotherapy for human cancers. The tumor suppressor PTEN plays a pivotal role in the growth of human cancer cells. We investigated whether costimulation of PPARgamma and RAR could synergistically up-regulate PTEN in human leukemia cells and consequently potentiate the inhibition of growth and cell cycle progression of these cells. We found that overexpression of PTEN with the adenoviral vector Ad/PTEN caused growth arrest at the G1 phase of the cell cycle of HL-60 cells. HL-60 cells treated with either a PPARgamma ligand (ciglitazone) or a RAR ligand (all-trans retinoic acid [ATRA]) up-regulated PTEN in HL-60 cells. The 2 compounds in combination showed synergistic effects on PTEN expression at the protein and messenger RNA levels. Moreover, the combination of ciglitazone and ATRA synergistically reduced cell growth rates and cell cycle arrest at the G1 phase. Our results suggest that, PPARgamma and RAR play an important role in controlling the growth of leukemia cells via the up-regulation of PTEN.

Amphiphilic triblock copolymer poly(p-dioxanone-co-L-lactide)-block-poly(ethylene glycol), enhancement of gene expression and inhibition of lung metastasis by aerosol delivery

We describe the development of an aerosol system for topical gene delivery to the lungs of C57BL/6 mice. This system is based on the combination of the commercial cationic lipid Lipofectin with a novel amphiphilic triblock copolymer, poly(p-dioxanone-co-L-lactide)-block-poly(ethylene glycol) (PPDO/PLLA-b-PEG, and abbreviated in the text as polymeric micelles). After optimizing conditions for DNA delivery to the lungs of mice using the combination of polymeric micelles with Lipofectin and LacZ DNA, we used the Lipofectin/polymeric micelle system to deliver the tumor suppressor gene PTEN to the lungs of C57BL/6 mice bearing the B16-F10 melanoma. Lipofectin/PTEN/polymeric micelles significantly improved gene expression of PTEN in the lungs of mice with no evidence of cell toxicity or acute inflammation. Importantly, lung metastasis, as measured by lung weight, was significantly reduced (P<0.001), as were total tumor foci in the lungs (P<0.001) and size of individual tumor nodules in animals treated with Lipofectin/PTEN/polymeric micelles compared with control animals. Survival time was also extended. These results suggest that the Lipofectin/polymeric micelle system is appropriate for enhancing gene delivery in vivo and that it can be applied as a non-invasive gene therapy for lung cancer.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) reduces vascular endothelial growth factor expression in allergen-induced airway inflammation

Vascular endothelial growth factor (VEGF) plays a pivotal role in the pathogenesis of bronchial asthma. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) has been implicated in regulating cell survival signaling through the phosphoinositide 3-kinase (PI3K)/Akt pathway. The key role of PI3K in VEGF-mediated signal transduction is established. However, the effects of PTEN on VEGF-mediated signaling in asthma are unknown. This study aimed to determine the effect of PI3K inhibitors and PTEN on VEGF expression in allergen-induced airway inflammation. We have used a female C57BL/6 mouse model for asthma to determine the role of PTEN in allergen-induced airway inflammation, specifically in the expression of VEGF. Allergen-induced airway inflammation leads to increased activity of PI3K in lung tissue. These mice develop the following typical pathophysiological features of asthma in the lungs: increased numbers of inflammatory cells of the airways; airway hyper-responsiveness; increased expression of interleukin (IL)-4, IL-5, IL-13, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, regulated on activation normal T cell expressed and secreted (RANTES), and eotaxin; increased vascular permeability; and increased levels of VEGF. Administration of PI3K inhibitors or adenoviruses carrying PTEN cDNA reduced the symptoms of asthma and decreased the increased levels of plasma extravasation and VEGF in allergen-induced asthmatic lungs. These results indicate that PTEN reduces VEGF expression in allergen-induced airway inflammation.

The Akt pathway in human breast cancer: a tissue-array-based analysis

The Akt pathway, an important regulator of cell proliferation and survival, is deregulated in many cancers. The pathway has achieved considerable importance due to the development of kinase inhibitors that are able to successfully reduce tumor growth. This study was conducted to determine the status of the Akt pathway in human breast cancers and to study the relationship between the different component proteins. Expression levels of PTEN, phosphorylated forms of the constituent proteins (Akt, FKHR, mTOR, and S6) and cyclin D1 were evaluated by immunohistochemistry, on consecutive sections from a tissue microarray containing 145 invasive breast cancers and 140 pure ductal carcinomas in-situ. Aberrant expression was correlated statistically with tumor characteristics and disease outcome. The Akt pathway was found to be activated early in breast cancer, in the in-situ stage. In all, 33, 15, 32, and 60% of ductal carcinoma in-situ showed overexpression of Akt, FKHR, mTOR, and cyclin D1. PTEN loss did not correlate statistically with expression of AKT or any of the other proteins with the exception of S6, indicating that Akt activation was not a result of PTEN loss. Expression levels of PTEN and S6 were significantly different in in-situ and invasive cancers, indicating association with disease progression. Loss of PTEN was noted in 11% of in-situ as compared to 26% of invasive cancers, while S6 overexpression was seen in 47% in-situ and in 72% invasive cancers. High-grade carcinomas were associated with PTEN loss, while low-grade carcinomas with good prognostic features showed cyclin D1 overexpression and were associated with longer disease free survival. Additionally, cancers with mTOR overexpression showed a three times greater risk for disease recurrence. Overall, a large proportion of in-situ and invasive breast cancers overexpressed cyclinD1 and S6. Our results may have significant implications in the development and application of targeted therapy.

Roles of PDK-1 and PKN in regulating cell migration and cortical actin formation of PTEN-knockout cells

Mutations in the tumor suppressor protein PTEN (phosphatase and tensin homologue deleted on chromosome 10) enhance cell migration, yet the underlying molecular mechanisms remain largely uncharacterized. Loss of PTEN in mouse embryonic fibroblasts (MEFs) correlates with striking cortical actin accumulation. However, how loss of PTEN leads to cortical actin formation and whether the presence of cortical actin contributes to the increased cell migration are unclear. Here we show that overexpression of dominant-negative forms of (DN) PTEN, RhoA or its kinase-dead (KD) effector, PKN, inhibited cortical actin formation, indicating that cortical actin of Pten(-/-) MEFs is mediated by the PTEN/Rho/PKN pathway. However, neither DN RhoA nor KD PKN inhibited the enhanced migration of Pten(-/-) cells, in contrast to the inhibitory effect of DN Rac. In agreement with the previous observation that DN Akt inhibits migration of Pten(-/-) cells, we demonstrate here that overexpression of KD PDK-1, the Akt kinase, reduces Pten(-/-) cell migration. Furthermore, overexpression of DN forms of Akt, Rac, or PDK-1, all of which inhibit migration of Pten(-/-) cells, had no effect on cortical actin accumulation. Our findings suggest that PDK-1/Akt signaling pathway plays a major role in regulating cell migration induced by PTEN deficiency.

PTEN up-regulates the tumor metastasis suppressor gene Drg-1 in prostate and breast cancer

PTEN (phosphatase and tensin homologue deleted on chromosome 10) has been shown to be inactivated in a wide variety of cancers, and the role of this gene as a tumor suppressor has been well established. On the other hand, results of recent animal studies as well as clinical evidence indicate that PTEN is also involved in tumor metastasis suppression. Although PTEN is known to play a key role in controlling cell growth and apoptosis, how PTEN exerts the metastasis suppressor function remains largely unknown. Recently, a microarray analysis identified the Drg-1 gene (differentiation related gene 1) as one of the potential targets of PTEN. The Drg-1 gene has been shown to suppress tumor metastasis in animal models of prostate and colon cancer, and the expression of this gene is significantly reduced with advancement of prostate and breast cancers in clinical setting. In this study, we explored the possibility that PTEN controls tumor metastasis by regulating the expression of the Drg-1 gene. Our results indicate that overexpression of PTEN significantly augments the endogenous expression of Drg-1 protein, whereas inhibition of PTEN by small interfering RNA decreases Drg-1 in a dose- and time-dependent manner. We also found that the control of the Drg-1 gene by PTEN seems to be at the transcriptional level, and that a phospho-Akt inhibitor restores the Drg-1 expression, indicating that PTEN controls Drg-1 by an Akt-dependent pathway. Consistent with these results, our immunohistochemical analysis revealed that PTEN expression correlates significantly with Drg-1 in both prostate and breast cancer cases. Furthermore, combination of the two markers, PTEN and Drg-1, emerged as a significantly better predictor of prostate and breast cancer patient survival than either marker alone.

The assessment of PTEN tumor suppressor gene in combination with Gleason scoring and serum PSA to evaluate progression of prostate carcinoma

OBJECTIVE

The purpose of the study was to determine if the tumor suppressor gene phosphate and tensin homolog (PTEN) (mutated in multiple advanced cancers 1) in combination with Gleason scoring and serum prostate specific antigen (PSA) could be employed to better predict the progression of prostate carcinoma.

MATERIALS AND METHODS

The study group consisted of 43 patients with benign prostate hyperplasia (BPH), 15 with organ confined prostate carcinoma (OCPCa), and 18 with advanced prostate carcinoma (APCa). Prostate tissue samples were obtained from radical prostatectomy, transurethral resection, and TRUS guided trans-rectal needle biopsy and then evaluated for biomarker expression. The clinical stage was assessed according to tumor node metastasis classification and grade according to Gleason system. Serum PSA was measured by conventional techniques and Western blotting analysis was used to determine PTEN expression in the primary tissue. Multivariate analysis was performed to analyze whether these markers could individually predict the progression of prostate carcinoma.

RESULTS

APCa patients displayed higher Gleason scores and serum PSA levels. But much lower PTEN expression was detected in prostate of APCa patients compared to patients with BPH or OCPCa. Hormone refractory (HR) and hormone sensitive (HS) APCa cases did not yield any significant differences in terms of Gleason scoring, serum PSA and PTEN expression. PSA levels were significantly higher in patients with OCPCa or APCa compared to patients with BPH.

CONCLUSION

Our results suggested that both PTEN and serum PSA appeared to be useful as independent markers to depict the nature of tumor behavior as benign or malign. In addition, PTEN also appeared to be useful as an independent marker to predict the progression of prostate carcinoma.

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Pharmacogenetic candidate genes for melanoma

The incidence of melanoma is rising at an alarming rate and has become an important public health concern. If detected early, melanoma carries an excellent prognosis after appropriate surgical resection. Unfortunately, advanced melanoma has a poor prognosis and is notoriously resistant to radiation and chemotherapy. The relative resistance of melanoma to a wide-range of chemotherapeutic agents and high toxicity of current therapies has prompted a search for effective alternative treatments that would improve prognosis and limit side effects. Advances in molecular genetics are revealing in increasing detail the mechanisms responsible for the development of melanoma. Hopefully, elucidation of these pathways will provide a means of screening high-risk individuals and allow new drug development for prevention and treatment by identification of specific pharmacological targets. This review will summarize the genetics of melanoma with the goal of providing insights into potential pharmacogenetic candidate genes.

Dual-specificity phosphatase Pyst2-L is constitutively highly expressed in myeloid leukemia and other malignant cells

Northern blotting confirmed previous results indicating that the mitogen-activated protein kinase (MAPK) phosphatase Pyst2-L was highly expressed in leukocytes obtained from acute myeloid leukemia (AML) patients. High levels of Pyst2-L mRNA were expressed in bone marrow (BM) and peripheral leukocytes from nine AML and acute lymphoblastic leukemia (ALL) patients. BM from healthy individuals expressed very low levels of Pyst2-L. Whereas high levels of Pyst2-L mRNA and protein were detected in several leukemia cell lines, Pyst2-L mRNA was detected neither in 33/34 samples of normal peripheral blood mononuclear cells (PBMC) nor in leukocyte fractions enriched with CD34+ cells. Certain solid tumor and lymphoblastoid cell lines expressed high levels of Pyst2-L mRNA. In view of the association of Pyst2-L to MAPK signaling cascades, we tested if cell activation, a process involving MAPK signaling, influences Pyst2-L expression. Indeed, activation of T cells and endothelial cells increased Pyst2-L in these cells. Furthermore, TPA, a known MAPK activator, induces the expression of both Pyst2-L mRNA as well as the Pyst2-L protein in leukemia cells. This induction was partially inhibited by PD098059, an Mek1/2-specific inhibitor. Based on the results of this and previous studies, we hypothesize that the high levels of Pyst2-L detected in the active state of AML and ALL diseases and in other types of cancer reflect an altered MAPK signaling pathway in such malignant processes. This alteration may be the result of a failed attempt to counter the constitutive activation of MAPK in transformed cells or alternatively, may represent the activated state of such cells.

The genetics of malignant melanoma: lessons from mouse and man

Therapeutic resistance and proclivity for metastasis are hallmarks of malignant melanoma. Genetic, epidemiological and genomic investigations are uncovering the spectrum of stereotypical mutations that are associated with melanoma and how these mutations relate to risk factors such as ultraviolet exposure. The ability to validate the pathogenetic relevance of these mutations in the mouse, coupled with advances in rational drug design, has generated optimism for the development of effective prevention programmes, diagnostic measures and targeted therapeutics in the near future.

PTEN signaling pathways in melanoma

Phosphatase and tensin homolog deleted in from chromosome ten (PTEN), initially also known as mutated in multiple advanced cancers or TGF-beta-regulated and epithelia cell-enriched phosphatase, is a tumor suppressor gene that is mutated in a large fraction of human melanomas. A broad variety of human cancers carry PTEN alterations, including glioblastomas, endometrial, breast, thyroid and prostate cancers. The PTEN protein has at least two biochemical functions: it has both lipid phosphatase and protein phosphatase activity. The lipid phosphatase activity of PTEN decreases intracellular PtdIns(3,4,5)P(3) level and downstream Akt activity. Cell-cycle progression is arrested at G1/S, mediated at least partially through the upregulation of the cyclin-dependent kinase inhibitor p27. In addition, agonist-induced apoptosis is mediated by PTEN, through the upregulation of proapoptotic machinery involving caspases and BID, and the downregulation of antiapoptotic proteins such as Bcl2. The protein phosphatase activity of PTEN is apparently less central to its involvement in tumorigenesis. It is involved in the inhibition of focal adhesion formation, cell spreading and migration, as well as the inhibition of growth factor-stimulated MAPK signaling. Therefore, the combined effects of the loss of PTEN lipid and protein phosphatase activity may result in aberrant cell growth and escape from apoptosis, as well as abnormal cell spreading and migration. In melanoma, PTEN loss has been mostly observed as a late event, although a dose-dependent loss of PTEN protein and function has been implicated in early stages of tumorigenesis as well. In addition, loss of PTEN and oncogenic activation of RAS seem to occur in a reciprocal fashion, both of which could cooperate with CDKN2A loss in contribution to melanoma tumorigenesis.

Apoptosis and melanoma chemoresistance

Melanoma is the most aggressive form of skin cancer and is notoriously resistant to all current modalities of cancer therapy. A large set of genetic, functional and biochemical studies suggest that melanoma cells become 'bullet proof' against a variety of chemotherapeutic drugs by exploiting their intrinsic resistance to apoptosis and by reprogramming their proliferation and survival pathways during melanoma progression. In recent years, the identification of molecules involved in the regulation and execution of apoptosis, and their alteration in melanoma, have provided new insights into the molecular basis for melanoma chemoresistance. With this knowledge in hand, the challenge is now to devise strategies potent enough to compensate or bypass these cell death defects and improve the actual poor prognosis of patients at late stages of the disease.

Involvement of PTEN in airway hyperresponsiveness and inflammation in bronchial asthma

Phosphatase and tensin homologue deleted on chromosome ten (PTEN) is part of a complex signaling system that affects a variety of important cell functions. PTEN blocks the action of PI3K by dephosphorylating the signaling lipid phosphatidylinositol 3,4,5-triphosphate. We have used a mouse model for asthma to determine the effect of PI3K inhibitors and PTEN on allergen-induced bronchial inflammation and airway hyperresponsiveness. PI3K activity increased significantly after allergen challenge. PTEN protein expression and PTEN activity were decreased in OVA-induced asthma. Immunoreactive PTEN localized in epithelial layers around the bronchioles in control mice. However, this immunoreactive PTEN dramatically disappeared in allergen-induced asthmatic lungs. The increased IL-4, IL-5, and eosinophil cationic protein levels in bronchoalveolar lavage fluids after OVA inhalation were significantly reduced by the intratracheal administration of PI3K inhibitors or adenoviruses carrying PTEN cDNA (AdPTEN). Intratracheal administration of PI3K inhibitors or AdPTEN remarkably reduced bronchial inflammation and airway hyperresponsiveness. These findings indicate that PTEN may play a pivotal role in the pathogenesis of the asthma phenotype.

Expression and significance of PTEN, hypoxia-inducible factor-1 alpha in colorectal adenoma and adenocarcinoma

AIM: To investigate the expression and significance of PTEN, hypoxia-inducible factor-1 alpha (HIF-1α), and targeting gene VEGF during colorectal carciogenesis.

METHODS: Total 71 cases colorectal neoplasms (9 cases of colorectal adenoma and 62 colorectal adenocarcinoma) were formalin fixed and paraffin-embedded, and all specimens were evaluated for PTEN mRNA, HIF-1α mRNA and VEGF protein expression. PTEN mRNA, HIF-1α mRNA were detected by in situ hybridization. VEGF protein was identified by citrate-microwave SP immunohistochemical method.

RESULTS: There were significant differences in PTEN, HIF-1α and VEGF expression between colorectal adenomas and colorectal adenocarcinoma (P < 0.05). The level of PTEN expression decreased as the pathologic stage increased. Conversely, HIF-1α and VEGF expression increased with the Dukes stage as follows: stage A (0.1029 ± 0.0457: 0.1207 ± 0.0436), stage B (0.1656 ± 0.0329: 0.1572 ± 0.0514), and stage C + D (0.2335 ± 0.0748: 0.2219 ± 0.0803). For PTEN expression, there was a significant difference among Dukes stage A, B, and C + D, and the level of PTEN expression was found to be significant higher in Dukes stage A or B than that of Dukes stage C or D. For HIF-1α expression, there was a significant difference between Dukes stage A and B, and the level of HIF-1α expression was found to be significantly higher in Dukes stage C+D than that of Dukes stage A or B. The VEGF expression had similar results as HIF-1α expression. In colorectal adenocarcinoma, decreased levels of PTEN were significantly associated with increased expression of HIF-1α mRNA (r = -0.36, P < 0.05) and VEGF protein (r = -0.48, P < 0.05) respectively. The levels of HIF-1 were positively correlated with VEGF expression (r = 0.71, P < 0.01).

CONCLUSION: Loss of PTEN expression and increased levels of HIF-1α and VEGF may play an important role in carcinogenesis and progression of colorectal adenocarcinoma.

Type 1 insulin-like growth factor regulates MT1-MMP synthesis and tumor invasion via PI 3-kinase/Akt signaling

The membrane type 1 matrix metalloproteinase (MT1-MMP) has been identified as a major activator of MMP-2 - a process involving the formation of a trimolecular complex with TIMP-2. We previously identified the IGF-I receptor as a positive regulator of MMP-2 synthesis. Here, we investigated the role of IGF-IR in the regulation of MT1-MMP. Highly invasive Lewis lung carcinoma subline H-59 cells express MT1-MMP and utilize it to activate their major extracellular matrix degrading proteinase-MMP-2. These cells were transiently transfected with a plasmid vector expressing a luciferase reporter gene downstream of the mouse MT1-MMP promoter. IGF-I treatment increased luciferase activity in the transfected cells by up to 10-fold and augmented endogenous MT1-MMP mRNA and protein synthesis by up to 2-3-fold, relative to controls. MT1-MMP induction and invasion were blocked by the PI 3-kinase inhibitors LY294002 and wortmannin and by rapamycin, but not by the MEK inhibitor PD98059. Overexpression of a dominant negative Akt mutant or of the tumor suppressor phosphatase and tensin homologue, PTEN, in these cells also caused a significant reduction in MT1-MMP expression and invasion. The results demonstrate that IGF-IR controls tumor cell invasion by coordinately regulating MMP-2 expression and its MT1-MMP-mediated activation and identify PI 3-kinase/Akt/mTOR signaling as critical to this regulation.

PTEN encoding product: A marker for tumorigenesis and progression of gastric carcinoma

AIM: To detect the expression of PTEN encoding product in normal mucosa, intestinal metaplasia (IM), dysplasia and carcinoma of the stomach, and to investigate its clinical implication in tumorigenesis and progression of gastric carcinoma.

METHODS: Formalin-fixed paraffin embedded specimens from 184 cases of gastric carcinoma, their adjacent normal mucosa, IM and dysplasia were evaluated for PTEN protein expression by SABC immunohistochemistry. PTEN expression was compared with tumor stage, lymph node metastasis, Lauren’s and WHO’s histological classification of gastric carcinoma. Expression of VEGF was also detected in 60 cases of gastric carcinoma and its correlation with PTEN was concerned.

RESULTS: The positive rates of PTEN protein were 100% (102/102), 98.5% (65/66), 66.7% (4/6) and 47.8% (88/184) in normal mucosa, IM, dysplasia and carcinoma of the stomach, respectively. The positive rates in dysplasia and carcinoma were lower than in normal mucosa and IM (P < 0.01). Advanced gastric cancers expressed less frequent PTEN than early gastric cancer (42.9% vs 67.6%, P < 0.01). The positive rate of PTEN protein was lower in gastric cancer with than without lymph node metastasis (40.3% vs 63.3%, P < 0.01). PTEN was less expressed in diffuse-type than in intestinal-type gastric cancer (41.5% vs 57.8%, P < 0.05). Signet ring cell carcinoma showed the expression of PTEN at the lowest level (25.0%, 7/28); less than well and moderately differentiated ones (P < 0.01). Expression of PTEN was not correlated with expression of VEGF (P > 0.05).

CONCLUSION: Loss or reduced expression of PTEN protein occures commonly in tumorigenesis and progression of gastric carcinoma. It is suggested that PTEN can be an objective marker for pathologically biological behaviors of gastric carcinoma.

Loss of cellular adhesion to matrix induces p53-independent expression of PTEN tumor suppressor

BACKGROUND

The tumor suppressor gene PTEN has been found mutated in many types of advanced tumors. When introduced into tumor cells that lack the wild-type allele of the gene, exogenous PTEN was able to suppress their ability to grow anchorage-independently, and thus reverted one of the typical characteristics of tumor cells. As these findings indicated that PTEN might be involved in the regulation of anchorage-dependent cell growth, we analyzed this aspect of PTEN function in non-tumor cells with an anchorage-dependent phenotype.

RESULTS

We found that in response to the disruption of cell-matrix interactions, expression of endogenous PTEN was transcriptionally activated, and elevated levels of PTEN protein and activity were present in the cells. These events correlated with decreased phosphorylation of focal adhesion kinase, and occurred even in the absence of p53, a tumor suppressor protein and recently established stimulator of PTEN transcription.

CONCLUSIONS

In view of PTEN's potent growth-inhibitory capacity, we conclude that its induction after cell-matrix disruptions contributes to the maintenance of the anchorage-dependent phenotype of normal cells.