Guijarro M.V.,New York University |
Vergel M.,Hospital Universitario Virgen Del Rocio |
Marin J.J.,Hospital Universitario Virgen Del Rocio |
Marin J.J.,University of Seville |
And 6 more authors.
Oncogene | Year: 2012
MAP17 is a small, 17-kDa, non-glycosylated membrane protein that is overexpressed in a percentage of carcinomas. In the present work, we have analyzed the role of MAP17 expression during mammary cancer progression. We have found that MAP17 is expressed in 60% human mammary tumors while it is not expressed in normal or benign neoplasias. MAP17 levels increased with breast tumor stage and were strongly correlated with mammary tumoral progression. A significant increase in the levels of reactive oxygen species (ROS) was observed in MAP17-expressing cells, as compared with parental cells. This increase was further paralleled by an increase in the tumorigenic capacity of carcinoma cells but not in immortal non-tumoral breast epithelial cells, which provides a selective advantage once tumorigenesis has begun. Expression of specific MAP17 shRNA in protein-expressing tumor cells reduced their tumorigenic capabilities, which suggests that this effect is dependent upon MAP17 protein expression. Our data show that ROS functions as a second messenger that enhances tumoral properties, which are inhibited in non-tumoral cells. We have found that p38α activation mediates this response. MAP17 triggers a ROS-dependent, senescence-like response that is abolished in the absence of p38a activation. Furthermore, in human breast tumors, MAP17 activation is correlated with a lack of phosphorylation of p38α. Therefore, MAP17 is overexpressed in late-stage breast tumors, in which oncogenic activity relies on p38 insensitivity to induce intracellular ROS. ©2012 Macmillan Publishers Limited.
Macdonald A.I.,University of Glasgow |
Sun P.,University of Glasgow |
Sun P.,University of Texas M. D. Anderson Cancer Center |
Hernandez-Lopez H.,University of Glasgow |
And 9 more authors.
Biochemical Journal | Year: 2012
Gap junctions, composed of Cxs (connexins), allow direct intercellular communication. Gap junctions are often lost during the development of malignancy, although the processes behind this are not fully understood. Cx43 is a widely expressed Cx with a long cytoplasmic C-terminal tail that contains several potential protein-interaction domains. Previously, in a model of cervical carcinogenesis, we showed that the loss of gap junctional communication correlated with relocalization of Cx43 to the cytoplasm late in tumorigenesis. In the present study, we demonstrate a similar pattern of altered expression for the hDlg (human discs large) MAGUK (membrane-associated guanylate kinase) family tumour suppressor protein in cervical tumour cells, with partial co-localization of Cx43 and hDlg in an endosomal/lysosomal compartment. Relocalization of these proteins is not due to a general disruption of cell membrane integrity or Cx targeting. Cx43 (via its C-terminus) and hDlg interact directly in vitro and can form a complex in cells. This novel interaction requires the N- and C-termini of hDlg. hDlg is not required for Cx43 internalization inW12GPXY cells. Instead, hDlg appears to have a role in maintaining a cytoplasmic pool of Cx43. These results demonstrate that hDlg is a physiologically relevant regulator of Cx43 in transformed epithelial cells. © The Authors Journal compilation © 2012 Biochemical Society.
Ferrer I.,Institute Biomedicina Of Seville Huvr |
Ferrer I.,Institute Dinvestigacio Biomedica Of Bellvitge Idibell |
Blanco-Aparicio C.,Institute Biomedicina Of Seville Huvr |
Peregrina S.,Institute Biomedicina Of Seville Huvr |
And 8 more authors.
Cell Cycle | Year: 2011
The scaffold protein Spinophilin (SPN) is a regulatory subunit of phosphatase1a located at 17q21.33. This region is frequently associated with microsatellite instability and LOH containing a relatively high density of known tumor suppressor genes, including BRCA1. Several linkage studies have suggested the existence of an unknown tumor suppressor gene distal to BRCA1. Spn may be this gene but the mechanism through this gene make its contribution to cancer has not been described. In this study, we aimed to determine how loss of Spn may contribute to tumorigenesis. We explored the contribution of SPN to PP 1a-mediated Rb regulation. We found that the loss of Spn downregulated PPP 1CA and PP 1a activity, resulting in a high level of phosphorylated Rb, and increased ARF and p53 activity. However, in the absence of p53, reduced levels of SPN enhanced the tumorigenic potential of the cells. Furthermore, the ectopic expression of SPN in human tumor cells greatly reduced cell growth. Taken together, our results demonstrate that the loss of Spn induces a proliferative response by increasing Rb phosphorylation, which in turn activates p53, thereby, neutralizing the proliferative response. We suggest that Spn may be the tumor suppressor gene located at 17q21.33 acting through Rb regulation. © 2011 Landes Bioscience.
Molina-Pinelo S.,Institute Biomedicina Of Seville |
Ferrer I.,Spanish National Cancer Research Center |
Blanco-Aparicio C.,Spanish National Cancer Research Center |
Peregrino S.,Spanish National Cancer Research Center |
And 10 more authors.
Journal of Pathology | Year: 2011
The scaffold protein spinophilin (Spn, PPP1R9B) is one of the regulatory subunits of phosphatase-1a (PP1), targeting it to distinct subcellular locations and to its target. Loss of Spn reduces PPP1CA levels, thereby maintaining higher levels of phosphorylated pRb. This effect contributes to an increase in p53 activity. However, in the absence of p53, reduced levels of Spn increase the tumourigenic properties of cells. In addition, Spn knockout mice have a reduced lifespan, an increased number of tumours and increased cellular proliferation in some tissues, such as the mammary ducts. In addition, the combined loss of Spn and p53 activity leads to an increase in mammary carcinomas, confirming the functional relationship between p53 and Spn. In this paper, we report that Spn is absent in 20% and reduced in another 37% of human lung tumours. Spn reduction correlates with malignant grade. Furthermore, the loss of Spn also correlates with p53 mutations. Analysis of miRNAs in a series of lung tumours showed that miRNA106a* targeting Spn is over-expressed in some patients, correlating with decreased Spn levels. Proof-of-concept experiments over-expressing miRNA106a* or Spn shRNA in lung tumour cells showed increased tumourigenicity. In conclusion, our data showed that miRNA106a* over-expression found in lung tumours might contribute to tumourigenesis through Spn down-regulation in the absence of p53. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Galan-Moya E.M.,Centro Regional Of Investigaciones Biomedicas |
de la Cruz-Morcillo M.A.,Centro Regional Of Investigaciones Biomedicas |
Valero M.L.,Centro Regional Of Investigaciones Biomedicas |
Callejas-Valera J.L.,Centro Regional Of Investigaciones Biomedicas |
And 6 more authors.
PLoS ONE | Year: 2011
The p38 MAPK signaling pathway has been proposed as a critical mediator of the therapeutic effect of several antitumor agents, including cisplatin. Here, we found that sensitivity to cisplatin, in a system of 7 non-small cell lung carcinoma derived cell lines, correlated with high levels of MKK6 and marked activation of p38 MAPK. However, knockdown of MKK6 modified neither the response to cisplatin nor the activation of p38 MAPK. Deeper studies showed that resistant cell lines also displayed higher basal levels of MKK3. Interestingly, MKK3 knockdown significantly decreased p38 phosphorylation upon cisplatin exposure and consequently reduced the response to the drug. Indeed, cisplatin poorly activated MKK3 in resistant cells, while in sensitive cell lines MKK3 showed the opposite pattern in response to the drug. Our data also demonstrate that the low levels of MKK6 expressed in resistant cell lines are the consequence of high basal activity of p38 MAPK mediated by the elevated levels of MKK3. This finding supports the existence of a regulatory mechanism between both MAPK kinases through their MAPK. Furthermore, our results were also mirrored in head and neck carcinoma derived cell lines, suggesting our observations boast a potential universal characteristic in cancer resistance of cisplatin. Altogether, our work provides evidence that MKK3 is the major determinant of p38 MAPK activation in response to cisplatin and, hence, the resistance associated with this MAPK. Therefore, these data suggest that the balance between both MKK3 and MKK6 could be a novel mechanism which explains the cellular response to cisplatin. © 2011 Galan-Moya et al.