N4 -aryl substituted thiosemicarbazones derived from 1-indanones as potential anti-tumor agents for breast cancer treatment.

Breast cancer is the first cause of cancer death in women. Many patients are resistant to current therapies, and even those were sensitive at first may eventually become resistant later. Thiosemicarbazones (TSCs) are synthetic compounds that exhibit several pharmacological activities. In this study, we investigated the potential anti-tumor activity of a set of N4 -arylsubstituted TSCs (N4 -TSCs) on human breast cancer cell lines. Studies on the effect of N4 -TSCs (T1, T2, and T3) were carried on MCF-7, MDA-MB 231, and BT 474 cell lines which differ in their expression of ER, PR, and Her2/neu. Non-transformed MCF-10A breast cell line were used as normal cells. Action of N4 -TSCs were evaluated by proliferation assay, quantification of apoptosis and cell cycle analysis. Modulation of clonogenic efficiency and migratory capacity by N4 -TSCs were also evaluated. We further investigated the effects of N4 -TSCs on ROS level and Ribonucleotide Reductase (RR) activity. We analyzed the action of these compounds on cellular mammosphere-forming capacity. We found that T1 and T2 had specific anti-tumor effect on all breast cancer cell lines based on their pro-apoptotic action and inhibitory effect on clonogenic efficiency and cell migration capacity. We also showed that both compounds increased ROS level and inhibited RR activity. Finally, we found that all N4 -TSCs diminished mammospehere-forming capacity of MCF-7 and BT 474 cells. N4 -TSCs showed specific anti-tumor action on human breast cancer cells independently their biomarkers expression pattern. Our results place these compounds as promising novel anti-tumor drugs with potential therapeutic application against different types of breast cancer.

Breast cancer stem cells are involved in Trastuzumab resistance through the HER2 modulation in 3D culture.

Breast cancer human cells culture as spheroids develop autophagy and apoptosis, which promotes Trastuzumab resistance in HER2 overexpressing cells. Our aim was to study the association of the hostile environment developed in 3D with the breast cancer stem cells population and the HER2 modulation. Human mammary adenocarcinoma cell lines were cultured as spheroids using the hanging drop method. We generated hypoxia conditions by using a hypoxic chamber and CoCl2 treatment. Breast cancer stem cells were measured with mammosphere assays, the analysis of CD44 + CD24low population by flow cytometry and the pluripotent gene expression by RT-qPCR. HER2 expression was evaluated by flow cytometry and Western blot. MTS assays were conducted to study cell viability. Hostil environment developed in spheroids, defined by hypoxia and autophagy, modulated the response to Trastuzumab. In HER2+ cells with acquired resistance, we observed an increase in the breast cancer stem cell population. In BT474 spheroids, Trastuzumab induced the acquisition of resistance, along with an increase in breast cancer stem cells. Also, in 3D culture conditions we determined a modulation in the HER2 expression. Moreover, breast cancer stem cells showed enhanced HER2 expression. Finally, cells without HER2 gene amplification cultured as spheroids were sensitive to Trastuzumab, diminishing HER2 expression and cancer stem cells. Our findings show that 3D architecture is able to modulate breast cancer stem cell population and HER2 distribution, modifying the cell response to Trastuzumab.

The Immune System As a New Possible Cell Target for AFP 464 in a Spontaneous Mammary Cancer Mouse Model.

Aminoflavone (AFP 464, NSC 710464), an antitumor agent which recently entered phase II clinical trials, acts against estrogen-positive breast cancer (ER+). AFP 464, which has a unique mechanism of action by activating aryl hydrocarbon receptor (AhR) signaling pathway, decreased tumor size, and growth rate in the estrogen dependent, Tamoxifen-sensitive spontaneous M05 mouse model. Considering that AhR has recently emerged as a physiological regulator of the innate and adaptive immune responses, we investigated whether AFP 464 modulates the immune response in our mouse model. Studies on the effect of AFP 464 on the immune system were carried in BALB/c mice bearing M05 semi-differentiated mammary adenocarcinomas that express estrogen and progesterone receptors. Splenic cells and tumor inflammatory infiltrates were studied by cytometric analyses. The modulation of splenocytes cytotoxic activity by AFP 464 was also evaluated. We further investigated the effects of AFP 464 on peritoneal macrophages by evaluating metalloproteinase, arginase, and iNOS activities. We found that AFP 464 increased splenic cytotoxic activity, diminished the number of systemic and local Treg lymphocytes, and MDSCs, and induced a M1 phenotype in peritoneal macrophages of M05 tumor bearing mice. Therefore, we conclude that AFP 464 modulates immune response which collaborates with its anti-tumor activity. Our results place the immune system as a novel target for this anti-cancer agent to strengthen the rationale for its inclusion in breast cancer treatment regimens. J. Cell. Biochem. 118: 2841-2849, 2017. © 2017 Wiley Periodicals, Inc.

Therapeutic blockade of Foxp3 in experimental breast cancer models.

PURPOSE: Regulatory T cells (Tregs) impair the clinical benefit of cancer immunotherapy. To optimize the antitumor efficacy of therapeutic dendritic cell (DC) vaccines, we aimed to inhibit Foxp3, a transcription factor required for Treg function. METHODS: Mice bearing established syngeneic LM3 and 4T1 breast tumors were treated with antitumor DC vaccines and a synthetic peptide (P60) that has been shown to inhibit Foxp3. RESULTS: Treatment with P60 improved the therapeutic efficacy of DC vaccines in these experimental models. In addition, monotherapy with P60 inhibited tumor growth in immunocompetent as well as in immuno-compromised animals bearing established tumors. We found expression of Foxp3 in human and murine breast tumor cells. P60 inhibited IL-10 secretion in breast cancer cells that expressed Foxp3. CONCLUSIONS: Our results suggest that Foxp3 blockade improves the therapeutic efficacy of DC vaccines by inhibition of Tregs and through a direct antitumor effect. This strategy could prove useful to neutralize the immunosuppressive microenvironment and to boost antitumor immunity in breast cancer.

The synthetic peptide CIGB-300 modulates CK2-dependent signaling pathways affecting the survival and chemoresistance of non-small cell lung cancer cell lines.

BACKGROUND: Lung cancer is the most frequently diagnosed cancer and the leading cause of cancer-related deaths worldwide. Up to 80% of cancer patients are classified as non-small-cell lung cancer (NSCLC) and cisplatin remains as the gold standard chemotherapy treatment, despite its limited efficacy due to both intrinsic and acquired resistance. The CK2 is a Ser/Thr kinase overexpressed in various types of cancer, including lung cancer. CIGB-300 is an antitumor peptide with a novel mechanism of action, since it binds to CK2 substrates thus preventing the enzyme activity. The aim of this work was to analyze the effects of CIGB-300 treatment targeting CK2-dependent signaling pathways in NSCLC cell lines and whether it may help improve current chemotherapy treatment. METHODS: The human NSCLC cell lines NCI-H125 and NIH-A549 were used. Tumor spheroids were obtained through the hanging-drop method. A cisplatin resistant A549 cell line was obtained by chronic administration of cisplatin. Cell viability, apoptosis, immunoblotting, immunofluorescence and luciferase reporter assays were used to assess CIGB-300 effects. A luminescent assay was used to monitor proteasome activity. RESULTS: We demonstrated that CIGB-300 induces an anti-proliferative response both in monolayer- and three-dimensional NSCLC models, presenting rapid and complete peptide uptake. This effect was accompanied by the inhibition of the CK2-dependent canonical NF-κB pathway, evidenced by reduced RelA/p65 nuclear levels and NF-κB protein targets modulation in both lung cancer cell lines, as well as conditionally reduced NF-κB transcriptional activity. In addition, NF-κB modulation was associated with enhanced proteasome activity, possibly through its α7/C8 subunit. Neither the peptide nor a classical CK2 inhibitor affected cytoplasmic ß-CATENIN basal levels. Given that NF-κB activation has been linked to cisplatin-induced resistance, we explored whether CIGB-300 could bring additional therapeutic benefits to the standard cisplatin treatment. We established a resistant cell line that showed higher p65 nuclear levels after cisplatin treatment as compared with the parental cell line. Remarkably, the cisplatin-resistant cell line became more sensitive to CIGB-300 treatment. CONCLUSIONS: Our data provide new insights into CIGB-300 mechanism of action and suggest clinical potential on current NSCLC therapy.

Differential response of myeloid-derived suppressor cells to the nonsteroidal anti-inflammatory agent indomethacin in tumor-associated and tumor-free microenvironments.

Myeloid-derived suppressor cells (MDSCs) are key regulatory cells that control inflammation and promote tumor-immune escape. To date, no specific immunomodulatory drug has proven efficacy in targeting the expansion and/or function of these cells in different pathophysiologic settings. In this study, we identified a context-dependent effect of the nonsteroidal anti-inflammatory drug indomethacin (IND) on MDSCs, depending on whether they were derived from tumor microenvironments (TME) or from tumor-free microenvironments (TFME). Treatment of mice bearing the LP07 lung adenocarcinoma with IND inhibited the suppressive activity of splenic MDSCs, which restrained tumor growth through mechanisms involving CD8(+) T cells. The same effect was observed when MDSCs were treated with IND and conditioned media from LP07 tumor cells in vitro. However, in the absence of a tumor context, IND enhanced the intrinsic suppressive function of MDSCs and amplified their protumoral activity. In a model of autoimmune neuroinflammation, IND-treated MDSCs differentiated in TFME attenuated inflammation, whereas IND-treated MDSCs differentiated in TME aggravated clinical symptoms and delayed resolution of the disease. Mechanistically, IND reduced arginase activity as well as NO and reactive oxygen species production in MDSCs differentiated in TME but not in TFME. Moreover, expression of the C/EBP-ß transcription factor isoforms correlated with the suppressive activity of IND-treated MDSCs. Our study unveils the dual and context-dependent action of IND, a drug that serves both as an anti-inflammatory and anticancer agent, which differentially affects MDSC activity whether these cells are derived from TME or TFME. These results have broad clinical implication in cancer, chronic inflammation and autoimmunity.

Involvement of protein kinase C α and δ activities on the induction of the retinoic acid system in mammary cancer cells.

It has been established that retinoids exert some of their effects on cell differentiation and malignant phenotype reversion through the interaction with different members of the protein kinase C (PKC) family. Till nowadays the nature and extension of this interaction is not well understood. Due to the cytostatic and differentiating effects of retinoids, in the present study we propose to evaluate whether the crosstalk between the retinoid system and the PKC pathway could become a possible target for breast cancer treatment. We could determine that ATRA (all-trans retinoic) treatment showed a significant growth inhibition due to (G1 or G2) cell cycle arrest both in LM3 and SKBR3, a murine and human mammary cell line respectively. ATRA also induced a remarkable increase in PKCα and PKCδ expression and activity. Interestingly, the pharmacological inhibition of these two PKC isoforms prevented the activation of retinoic acid receptors (RARs) by ATRA, indicating that both PKC isoforms are required for RARs activation. Moreover, PKCδ inhibition also impaired ATRA-induced RARα translocation to the nucleus. In vivo assays revealed that a combined treatment using ATRA and PKCα inhibitors prevented lung metastatic dissemination in an additive way. Our results clearly indicate that ATRA modulates the expression and activity of different PKCs. Besides inducing cell arrest, the activity of both PKC is necessary for the induction of the retinoic acid system. The combined ATRA and PKCα inhibitors could be an option for the hormone-independent breast cancer treatment.

Oral-specific ablation of Klf4 disrupts epithelial terminal differentiation and increases premalignant lesions and carcinomas upon chemical carcinogenesis.

BACKGROUND: Squamous cell carcinoma (SSC) of the head and neck is the sixth most common cancer and is rarely diagnosed in early stages. The transcription factor Krϋppel-like factor 4 (Klf4) suppresses cell proliferation and promotes differentiation. Inducible mice carrying an oral-specific ablation of Klf4 (K14-CreER(tam) /Klf4(flox/flox) ) develop mild dysplastic lesions and abnormal differentiation in the tongue. Aiming to analyze whether Klf4 cooperate in oral chemical carcinogenesis,we applied 4-nitroquinoline 1-oxide (4NQO), a tobacco surrogate, to this conditional Klf4 knockout mice. METHODS: K14-CreER(tam) /Klf4(flox/flox) and control mice were treated with 4NQO for 16 weeks and monitored until week 30. Histopathological samples were used for diagnostic purposes and immunofluorescence detection of epithelial differentiation markers. RESULTS: 4NQO-treated K14-CreER(tam) /Klf4(flox/flox) mice (Klf4KO 4NQO) showed a significant weight loss and developed more severe dysplastic lesions than control mice with 4NQO (P < 0.005). The Klf4KO 4NQO showed a tendency to higher incidence of oral SCC and a marked keratinization pattern in dysplasias, in situ carcinomas and SCC. Also, tongues derived from Klf4KO 4NQO mice exhibited reduced terminal differentiation as judged by cytokeratin 1 staining when compared with 4NQO-treated controls. CONCLUSIONS: Klf4 ablation results in more severe dysplastic lesions in oral mucosa, with a tendency to higher incidence of SCC, after chemical carcinogenesis. We show here, in a context similar to the human carcinogenesis, that absence of Klf4 accelerates carcinogenesis and correlates with the absence of cytokeratin 1 expression. These results suggest a potential role for KLF4 as a tumor suppressor gene for the tongue epithelium.

Impairing squamous differentiation by Klf4 deletion is sufficient to initiate tongue carcinoma development upon K-Ras activation in mice.

Oral squamous cell carcinoma (SCC) is among the most prevalent cancers in the world and is characterized by high morbidity and few therapeutic options. Like most cancers, oral SCC arises from a multistep process involving alterations of genes responsible for balancing proliferation and differentiation. Among these, Krϋppel-like factor 4 (Klf4) suppresses cell proliferation and promotes differentiation and thus helps to maintain epithelial homeostasis. However, the prevailing role of Klf4 in maintenance of normal homeostasis in oral epithelium has not been established in vivo. Here, we used an inducible oral-specific mice model to selectively ablate Klf4 in the oral cavity. We generated K14-CreER(Tam)/Klf4 (f/f) mice that survived to adulthood and did not present overt phenotype. However, histologically these mice showed dysplastic lesions, increased cell proliferation and abnormal differentiation in the tongue 4 months after induction, supporting a homeostatic role of Klf4 in the oral epithelia. Furthermore, by breeding these mutants with a transgenic line expressing at endogenous levels K-ras (G12D), we assessed the role of disrupting differentiation gene programs to the carcinogenesis process. The K14-CreER(TAM)/K-ras (G12D)/Klf4 (-) (/-) mice rapidly develop oral SCC in the tongue. Thus, our findings support the emerging notion that activation of differentiating gene programs may represent a barrier preventing carcinogenesis in epithelial cells harboring oncogenic mutations, and thus that molecules acting upstream and downstream of Klf4 may represent components of a novel tumor-suppressive pathway.

Contribution of individual PKC isoforms to breast cancer progression.

The protein kinase C (PKC) family of serine/threonine kinases has been intensively studied in cancer since their discovery as major receptors for the tumor-promoting phorbol esters. The contribution of each individual PKC isozyme to malignant transformation is only partially understood, but it is clear that each PKC plays different role in cancer progression. PKC deregulation is a common phenomenon observed in breast cancer, and PKC expression and localization are usually dynamically regulated during mammary gland differentiation and involution. In fact, the overexpression of several PKCs has been reported in malignant human breast tissue and breast cancer cell lines. In this review, we summarize the knowledge available on the specific roles of PKC isoforms in the development, progression, and metastatic dissemination of mammary cancer. We also discuss the role of PKC isoforms as therapeutic targets, and their potential as markers for prognosis or treatment response.

Involvement of PKC delta (PKCδ) in the resistance against different doxorubicin analogs.

Doxorubicin is an anti-tumor antibiotic widely used in the management of cancer patients. Its main mechanism of action involves the generation of DNA damage and the inhibition of topoisomerase II, promoting apoptosis. AD 198 is a novel doxorubicin analog devoid of DNA binding and topoisomerase II inhibitory capacities. It has been proposed that AD 198 induces apoptosis by activating protein kinase C delta (PKCδ); a PKC isoform described as growth inhibitory in a large number of cell types. We have previously demonstrated that PKCδ overexpression in NMuMG cells induced the opposite effect, promoting proliferation and cell survival. In this study, we found that PKCδ overexpression confers an enhanced cell death resistance against AD 198 cytotoxic effect and against AD 288, another doxorubicin analog that preserves its mechanism of action. These resistances involve PKCδ-mediated activation of two well-known survival pathways: Akt and NF-κB. While the resistance against AD 198 could be abrogated upon the inhibition of either Akt or NF-κB pathways, only NF-κB inhibition could revert the resistance to AD 288. Altogether, our results indicate that PKCδ increases cell death resistance against different apoptosis inductors, independently of their mechanism of action, through a differential modulation of Akt and NF-κB pathways. Our study contributes to a better understanding of the mechanisms involved in PKCδ-induced resistance and may greatly impact in the rationale design of isozyme-specific PKC modulators as therapeutic agents.

Generation and characterization of human insulin-releasing cell lines.

BACKGROUND: The in vitro culture of insulinomas provides an attractive tool to study cell proliferation and insulin synthesis and secretion. However, only a few human beta cell lines have been described, with long-term passage resulting in loss of insulin secretion. Therefore, we set out to establish and characterize human insulin-releasing cell lines. RESULTS: We generated ex-vivo primary cultures from two independent human insulinomas and from a human nesidioblastosis, all of which were cultured up to passage number 20. All cell lines secreted human insulin and C-peptide. These cell lines expressed neuroendocrine and islets markers, confirming the expression profile found in the biopsies. Although all beta cell lineages survived an anchorage independent culture, none of them were able to invade an extracellular matrix substrate. CONCLUSION: We have established three human insulin-releasing cell lines which maintain antigenic characteristics and insulin secretion profiles of the original tumors. These cell lines represent valuable tools for the study of molecular events underlying beta cell function and dysfunction.

Glypican-3 regulates migration, adhesion and actin cytoskeleton organization in mammary tumor cells through Wnt signaling modulation.

Glypican-3 (GPC3) is a proteoglycan involved in migration, proliferation and cell survival modulation in several tissues. There are many reports demonstrating a downregulation of GPC3 expression in some human tumors, including mesothelioma, ovarian and breast cancer. Previously, we determined that GPC3 reexpression in the murine mammary adenocarcinoma LM3 cells induced an impairment of their in vivo invasive and metastatic capacities together with a higher susceptibility to in vitro apoptosis. Currently, the signaling mechanism of GPC3 is not clear. First, it was speculated that GPC3 regulates the insulin-like growth factor (IGF) signaling system. This hypothesis, however, has been strongly challenged. Recently, several reports indicated that at least in some cell types GPC3 serves as a selective regulator of Wnt signaling. Here we provide new data demonstrating that GPC3 regulates Wnt pathway in the metastatic adenocarcinoma mammary LM3 cell line. We found that GPC3 is able to inhibit canonical Wnt signals involved in cell proliferation and survival, as well as it is able to activate non canonical pathway, which directs cell morphology and migration. This is the first report indicating that breast tumor cell malignant properties can be reverted, at least in part, by GPC3 modulation of Wnt signaling. Our results are consistent with the potential role of GPC3 as a metastasis suppressor.

Progestin effects on breast cancer cell proliferation, proteases activation, and in vivo development of metastatic phenotype all depend on progesterone receptor capacity to activate cytoplasmic signaling pathways.

Accumulating evidence indicates that progestins are involved in controlling mammary gland tumorigenesis. Here, we assessed the molecular mechanisms of progestin action in breast cancer models with different phenotypes. We examined C4HD cells, an estrogen (ER) and progesterone (PR) receptor-positive murine breast cancer model in which progestins exert sustained proliferative response, the LM3 murine metastatic mammary tumor cell line, which lacks PR and ER expression, and human PR null T47D-Y breast cancer cells. In addition to acting as a transcription factor, PR can also function as an activator of signaling pathways. To explore which of these two functions were involved in progestin responses, reconstitution experiments in the PR-negative models were performed with wild-type PR-B, with a DNA binding mutant C587A-PR, and with mutant PR-BmPro, which lacks the ability to activate cytoplasm signaling pathways. We found that in a cell context either ER-positive or -negative, progestins induced cell growth and modulation of matrix metalloproteinases-9 (MMP-9) and -2 (MMP-2), and urokinase-type plasminogen activator (uPA) activities, via MAPK and phosphatidylinositol 3-kinase/Akt pathways, in cells expressing wild-type PR-B or DNA binding mutant C587A-PR. In contrast, in cells expressing mutant PR-BmPro, progestins did not induce growth. We also found that unliganded PR expression conferred breast cancer cells an in vitro less proliferative phenotype, as compared with cells lacking PR expression. Modulation of this behavior occurred when PR was functioning either as transcription factor or as signaling activator. Finally, we for the first time demonstrated that progestins favor development of breast tumor metastasis via PR function as activator of signaling pathways. Our present findings provide mechanistic support to the design of a novel therapeutic intervention in PR-positive breast tumors involving blockage of PR capacity to activate cytoplasmic signaling.

Protein kinase C delta inhibits the production of proteolytic enzymes in murine mammary cells.

In previous studies we have determined that protein kinase C (PKC) delta, a widely expressed member of the novel PKC serine-threonine kinases, induces in vitro changes associated with the acquisition of a malignant phenotype in NMuMG murine mammary cells. In this study we show that PKCdelta overexpression significantly decreases urokinase-type plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP-9) production, two proteases associated with migratory and invasive capacities. This effect is markedly enhanced by treatment with phorbol 12-myristate 13-acetate (PMA). On the other hand, depletion of PKCdelta using RNAi led to a marked increase in both uPA and MMP-9 secretion, suggesting a physiological role for PKCdelta in controlling protease secretion. The MEK-1 inhibitor PD98059 reverted the characteristic pattern of proteases secretion and phospho-ERK1/2 up-regulation observed in PKCdelta overexpressors, suggesting that the PKCdelta effect is mediated by the MEK/ERK pathway. Our results suggest a dual role for PKCdelta in murine mammary cell cancer progression. While this kinase clearly promotes mitogenesis and favors malignant transformation, it also down-modulates the secretion of proteases probably limiting metastatic dissemination.

Dual activation of Toll-like receptors 7 and 9 impairs the efficacy of antitumor vaccines in murine models of metastatic breast cancer.

PURPOSE: Since combination of Toll-like receptor (TLR) ligands could boost antitumor immunity, we evaluated the efficacy of dendritic cell (DC) vaccines upon dual activation of TLR9 and TLR7 in breast cancer models. METHODS: DCs were generated from mouse bone marrow or peripheral blood from healthy human donors and stimulated with CpG1826 (mouse TLR9 agonist), CpG2006 or IMT504 (human TLR9 agonists) and R848 (TLR7 agonist). Efficacy of antitumor vaccines was evaluated in BALB/c mice bearing metastatic mammary adenocarcinomas. RESULTS: CpG-DCs improved the survival of tumor-bearing mice, reduced the development of lung metastases and generated immunological memory. However, dual activation of TLRs impaired the efficacy of DC vaccines. In vitro, we found that R848 inhibited CpG-mediated maturation of murine DCs. A positive feedback loop in TLR9 mRNA expression was observed upon CpG stimulation that was inhibited in the presence of R848. Impaired activation of NF-κB was detected when TLR9 and TLR7 were simultaneously activated. Blockade of nitric oxide synthase (NOS) and indoleamine-pyrrole-2,3-dioxygenase (IDO) improved the activation of CpG-DCs. When we evaluated the effect of combined activation of TLR9 and TLR7 in human DCs, we found that R848 induced robust DC activation that was inhibited by TLR9 agonists. CONCLUSIONS: These observations provide insight in the biology of TLR9 and TLR7 crosstalk and suggest caution in the selection of agonists for multiple TLR stimulation. Blockade of NOS and IDO could improve the maturation of antitumor DC vaccines. R848 could prove a useful adjuvant for DC vaccines in human patients.

Fibronectin is distinctly downregulated in murine mammary adenocarcinoma cells with high metastatic potential.

In the present work we used a murine mammary cancer model of two related adenocarcinomas with different lung metastasizing abilities, to compare their global gene expression profiles. Clontech Atlas mouse cDNA microarrays of primary cultured tumor cells were employed to identify genes that are modulated in the more metastatic variant MM3 relative to its parental tumor M3. A total of 88 from 1,176 genes were differentially expressed in MM3 primary cultures, most of them (n=86) were upregulated. Genes were grouped according to their functions as associated with signal transduction and transcription regulation (e.g. Stat1 and Zfp 92), with cell adhesion and motility (cadherin 1, fibronectin), with invasion and angiogenesis (uPA, 72 kDa MMP2), with the regulation of cell proliferation and cell death (cyclins G and A2, TNF), and also included growth factors and receptors, oncogenes and tumor suppressors genes (p107, TGFbeta2, TBR-I, PDGFR). Only 2 genes, TTF1 and fibronectin (FN), showed a significant downregulation. Notably FN expression, loss of which has been associated with a malignant phenotype, was reduced about 19-fold in the more metastatic MM3 cells. Previously known differences in expression patterns associated with the metastatic capacity of MM3 and M3 adenocarcinomas, including downregulation of FN or upregulated expression of TGFbeta and proteases, were confirmed by the array data. The fact that FN was one of the only two genes significantly down-regulated out of the 1,176 genes analyzed stresses the hypothesis that FN may behave as an important metastasis suppressor gene in mammary cancer.

Decreased mitochondrial nitric oxide synthase activity and hydrogen peroxide relate persistent tumoral proliferation to embryonic behavior.

Differential expression and activity of constitutive mitochondrial nitric oxide synthase (mtNOS) in the mitochondrial compartment is followed by significant variations in matrix nitric oxide (NO) steady-state concentration. The mitochondrial utilization of NO involves the production of superoxide anion and H(2)O(2), a species freely diffusible outside the mitochondria that participates in the modulation of cell proliferation and apoptosis and in cell transformation and cancer. On these bases, we analyzed the modulation of mtNOS in the frame of cellular redox state in M3, MM3, and P07 murine tumors and their respective cell lines, as compared with normal proliferating and quiescent tissues. The results showed that: (a) tumoral and proliferating mitochondria only retain 10-50% of the activity of complexes I, II-III, and IV and Mn-SOD of quiescent tissues; (b) normal proliferating tissues, like embryonic liver or pregnant mammary gland, have 10-20% of mtNOS expression and activity and mitochondrial H(2)O(2) yield than quiescent nonproliferating tissues; (c) similarly but irrespective of mtNOS expression, tumoral mitochondria have no >5% of mtNOS activity and H(2)O(2) yield of mature tissues; and (d) in opposition to stable tissues, both tumoral and normal proliferating cells exhibit high cyclin D1 expression and low pro-apoptotic p38mitogen-activated protein kinase activity. Dually, H(2)O(2) stimulated tumor cell proliferation (<10 microM) or markedly inhibited it (>10 microM) with parallel variations of cyclin D1, phospho-extracellular-regulated kinase1/2, and phospho-p38mitogen-activated protein kinase. It is surmised that decreased oxidative phosphorylation, defective tumoral mtNOS, and low mitochondrial NO-dependent H(2)O(2) may be a platform to link persistent tumoral growth to embryonic behavior.

Glypican-3 induces a mesenchymal to epithelial transition in human breast cancer cells.

Breast cancer is the disease with the highest impact on global health, being metastasis the main cause of death. To metastasize, carcinoma cells must reactivate a latent program called epithelial-mesenchymal transition (EMT), through which epithelial cancer cells acquire mesenchymal-like traits.Glypican-3 (GPC3), a proteoglycan involved in the regulation of proliferation and survival, has been associated with cancer. In this study we observed that the expression of GPC3 is opposite to the invasive/metastatic ability of Hs578T, MDA-MB231, ZR-75-1 and MCF-7 human breast cancer cell lines. GPC3 silencing activated growth, cell death resistance, migration, and invasive/metastatic capacity of MCF-7 cancer cells, while GPC3 overexpression inhibited these properties in MDA-MB231 tumor cell line. Moreover, silencing of GPC3 deepened the MCF-7 breast cancer cells mesenchymal characteristics, decreasing the expression of the epithelial marker E-Cadherin. On the other side, GPC3 overexpression induced the mesenchymal-epithelial transition (MET) of MDA-MB231 breast cancer cells, which re-expressed E-Cadherin and reduced the expression of vimentin and N-Cadherin. While GPC3 inhibited the canonical Wnt/ß-Catenin pathway in the breast cancer cells, this inhibition did not have effect on E-Cadherin expression. We demonstrated that the transcriptional repressor of E-Cadherin - ZEB1 - is upregulated in GPC3 silenced MCF-7 cells, while it is downregulated when GPC3 was overexpressed in MDA-MB231 cells. We presented experimental evidences showing that GPC3 induces the E-Cadherin re-expression in MDA-MB231 cells through the downregulation of ZEB1.Our data indicate that GPC3 is an important regulator of EMT in breast cancer, and a potential target for procedures against breast cancer metastasis.

Immortalized mammary epithelial cells overexpressing protein kinase C gamma acquire a malignant phenotype and become tumorigenic in vivo.

We have investigated the role of a classical isoform of protein kinase C (PKCgamma) in promoting immortalized mammary cell tumorigenesis in vivo and the contribution of proteases and adhesion molecules to this process. We hypothesized that overexpression of PKCgamma in immortalized mammary epithelial cells may initiate, by activating the mitogenic ERK pathway, early changes in proteases, adhesion molecules, and markers of an epithelium-to-mesenchyme transition that may contribute to in vivo tumorigenesis. Here we show that compared to vector-transfected cells, immortalized murine mammary epithelial cells (NMuMG) overexpressing PKCgamma have stronger activation of (approximately 5-fold) ERK1/2 MAPKs, which results in a similar increase in cyclin D1. In addition, PKCgamma-expressing cells showed increased levels of vimentin, fibronectin (FN), beta1-integrins, enhanced adhesion to fibronectin, and its organization into fibrils. Concomitantly, PKCgamma induced a dramatic down-regulation of E-cadherin protein levels and its localization to cell-cell junctions. NMuMG cells expressing PKCgamma became resistant to death by anoikis and formed colonies in soft agar. This effect was dependent on ERK activation, because Mek1/2 inhibition with PD98059 abrogated anchorage-independent growth. Most importantly, unlike control NMuMG cells, PKCgamma-transfected cells inoculated s.c. into nude mice displayed tumorigenic and invasive capacity and were able to spontaneously metastasize. This behavior correlated with increased production of uPA and MMPs-9/-2 induced by PKCgamma. These results suggest that PKCgamma overexpression in immortalized mammary epithelial cells may generate, through an increase in ERK, signaling changes in the expression of genes associated with an epithelium-to-mesenchyme transition that may be sufficient to favor tumor growth in vivo.