7 research outputs found
Prognostic value of CtIP/RBBP8 expression in breast cancer
CtIP/RBBP8 is a multifunctional protein involved in transcription, DNA replication, DNA repair by homologous recombination and the G1 and G2 checkpoints. Its multiple roles are controlled by its interaction with several specific factors, including the tumor suppressor proteins BRCA1 and retinoblastoma. Both its functions and interactors point to a putative oncogenic potential of CtIP/RBBP8 loss. However, CtIP/RBBP8 relevance in breast tumor appearance, development, and prognosis has yet to be established. We performed a retrospective analysis of CtIP/RBBP8 and RB1 levels by immunohistochemistry using 384 paraffin-embedded breast cancer biopsies obtained during tumor removal surgery. We have observed that low or no expression of CtIP/RBBP8 correlates with high-grade breast cancer and with nodal metastasis. Reduction on CtIP/RBBP8 is most common in hormone receptor (HR)-negative, HER2-positive, and basal-like tumors. We observed lower levels of RB1 on those tumors with reduced CtIP/RBBP8 levels. On luminal tumors, decreased but not absence of CtIP/RBBP8 levels correlate with increased disease-free survival when treated with a combination of hormone, radio, and chemo therapies.España Ministerio de Economía y Competitividad SAF2010-14877Junta de Andalucía, Consejería de Salud AI2013-A-000
Both p62/SQSTM1-HDAC6-dependent autophagy and the aggresome pathway mediate CDK1 degradation in human breast cancer
Cyclin-dependent kinase 1 (CDK1) is the central mammalian regulator of cell proliferation and a promising therapeutic target for breast cancer. In fact, CDK1 inhibition downregulates survival and induces apoptosis. Due to its essential role, CDK1 expression and activity are strictly controlled at various levels. We previously described that CDK1 stability is also regulated and that SCF(βTrCP) ubiquitinates CDK1, which is degraded via the lysosomal pathway. In addition, in breast tumors from patients, we found a negative correlation between CDK1 accumulation and βTrCP levels, and a positive correlation with the degree of tumor malignancy. This prompted us to study the molecular mechanism involved in CDK1 clearance. In this report, we determine that both chemotherapeutic agents and proteolytic stress induce CDK1 degradation in human breast cancer MCF7 cells through p62/HDAC6-mediated selective autophagy. On the one hand, CDK1 binds to p62/SQSTM1-LC3 and, on the other hand, it interacts with HDAC6. Both complexes are dependent on the presence of an intact βTrCP-binding motif on CDK1. Furthermore, we also show that CDK1 is recruited to aggresomes in response to proteasome inhibition for an extended period. We propose CDK1 clearance as a potential predictive biomarker of antitumor treatment efficacy
Obatoclax and Paclitaxel Synergistically Induce Apoptosis and Overcome Paclitaxel Resistance in Urothelial Cancer Cells
Paclitaxel is a treatment option for advanced or metastatic bladder cancer after the failure of first-line cisplatin and gemcitabine, although resistance limits its clinical benefits. Mcl-1 is an anti-apoptotic protein that promotes resistance to paclitaxel in different tumors. Obatoclax, a BH3 mimetic of the Bcl-2 family of proteins, antagonizes Mcl-1 and hence may reverse paclitaxel resistance in Mcl-1-overexpressing tumors. In this study, paclitaxel-sensitive 5637 and -resistant HT1197 bladder cancer cells were treated with paclitaxel, obatoclax, or combinations of both. Apoptosis, cell cycle, and autophagy were measured by Western blot, flow cytometry, and fluorescence microscopy. Moreover, Mcl-1 expression was analyzed by immunohistochemistry in bladder carcinoma tissues. Our results confirmed that paclitaxel alone induced Mcl-1 downregulation and apoptosis in 5637, but not in HT1197 cells; however, combinations of obatoclax and paclitaxel sensitized HT1197 cells to the treatment. In obatoclax-treated 5637 and obatoclax + paclitaxel-treated HT1197 cells, the blockade of the autophagic flux correlated with apoptosis and was associated with caspase-dependent cleavage of beclin-1. Obatoclax alone delayed the cell cycle in 5637, but not in HT1197 cells, whereas combinations of both retarded the cell cycle and reduced mitotic slippage. In conclusion, obatoclax sensitizes HT1197 cells to paclitaxel-induced apoptosis through the blockade of the autophagic flux and effects on the cell cycle. Furthermore, Mcl-1 is overexpressed in many invasive bladder carcinomas, and it is related to tumor progression, so Mcl-1 expression may be of predictive value in bladder cancer.España, Sistema Público Andaluz Biobanco y ISCIII-Red de Biobancos PT17/0015/004
βTrCP controls the lysosome-mediated degradation of CDK1, whose accumulation correlates with tumor malignancy
n mammals, cell cycle progression is controlled by cyclin-dependent kinases, among which CDK1 plays important roles in the regulation of the G2/M transition, G1 progression and G1/S transition. CDK1 is highly regulated by its association to cyclins, phosphorylation and dephosphorylation, changes in subcellular localization, and by direct binding of CDK inhibitor proteins. CDK1 steady-state protein levels are held constant throughout the cell cycle by a coordinated regulation of protein synthesis and degradation. We show that CDK1 is ubiquitinated by the E3 ubiquitin ligase SCFβTrCP and degraded by the lysosome. Furthermore, we found that DNA damage not only triggers the stabilization of inhibitory phosphorylation sites on CDK1 and repression of CDK1 gene expression, but also regulates βTrCP-induced CDK1 degradation in a cell type-dependent manner. Specifically, treatment with the chemotherapeutic agent doxorubicin in certain cell lines provokes CDK1 degradation and induces apoptosis, whereas in others it inhibits destruction of the protein. These observations raise the possibility that different tumor types, depending on their pathogenic spectrum mutations, may display different sensitivity to βTrCP-induced CDK1 degradation after DNA damage. Finally, we found that CDK1 accumulation in patients’ tumors shows a negative correlation with βTrCP and a positive correlation with the degree of tumor malignancy.España, Ministerio de Economía y Competitividad SAF2011-30003Junta de Andalucía, Dirección General de Investigación, Tecnología y Empresa P08- CVI-03603 and P10-CTS-6243
E-cadherin expression is associated with somatostatin analogue response in acromegaly
Acromegaly is a rare disease resulting from hypersecretion of growth hormone (GH)
and insulin‐like growth factor 1 (IGF1) typically caused by pituitary adenomas, which
is associated with increased mortality and morbidity. Somatostatin analogues (SSAs)
represent the primary medical therapy for acromegaly and are currently used as
first‐line treatment or as second‐line therapy after unsuccessful pituitary surgery.
However, a considerable proportion of patients do not adequately respond to SSAs
treatment, and therefore, there is an urgent need to identify biomarkers predictors
of response to SSAs. The aim of this study was to examine E‐cadherin expression
by immunohistochemistry in fifty‐five GH‐producing pituitary tumours and determine
the potential association with response to SSAs as well as other clinical and
histopathological features. Acromegaly patients with tumours expressing low E‐cadherin
levels exhibit a worse response to SSAs. E‐cadherin levels are associated with
GH‐producing tumour histological subtypes. Our results indicate that the immunohistochemical
detection of E‐cadherin might be useful in categorizing acromegaly
patients based on the response to SSAs.ISCIII‐Subdirección General de Evaluación y Fomento de la Investigación PI13/02043 PI16/00175FEDER PI13/02043 PI16/00175Junta de Andalucía A‐0023‐2015 A‐0003‐2016 CTS‐1406 BIO‐0139Andalusian Ministry of Health C‐0015‐2014CIBERobn PI13/ 02043 PI16/0017
Glycogen Synthase Kinase-3-ß (GSK3ß) negatively regulates PTTG1/human Securin protein stability, and GSK3ß inactivation correlates with securin accumulation in breast tumors.
PTTG1, also known as securin, is an inactivating partner of separase, the major effector for chromosome segregation during mitosis. At the metaphase-to-anaphase transition, securin is targeted for proteasomal destruction by the anaphase-promoting complex or cyclosome, allowing activation of separase. In addition, securin is overexpressed in metastatic or genomically instable tumors, suggesting a relevant role for securin in tumor progression. Stability of securin is regulated by phosphorylation; some phosphorylated forms are degraded out of mitosis, by the action of the SKP1-CUL1-F-box protein (SCF) complex. The kinases targeting securin for proteolysis have not been identified, and mechanistic insight into the cause of securin accumulation in human cancers is lacking. Here, we demonstrate that glycogen synthase kinase-3β (GSK3β) phosphorylates securin to promote its proteolysis via SCF(βTrCP) E3 ubiquitin ligase. Importantly, a strong correlation between securin accumulation and GSK3β inactivation was observed in breast cancer tissues, indicating that GSK3β inactivation may account for securin accumulation in breast cancers.Ministerio de Ciencia e Innovación de España SAF2008-03095 y SAF2008-05046Ministerio de Sanidad de España y Fondo Europeo de Desarrollo Regional (FEDER) ISCIII-RETIC-RD06/0020-FEDERDirección General de Investigación, Tecnología y Empresa, Junta de Andalucía P08-CVI-03603 y PI09-058
Methylation alterations are not a major cause of PTTG1 misregulation
Background: On its physiological cellular context, PTTG1 controls sister chromatid segregation
during mitosis. Within its crosstalk to the cellular arrest machinery, relies a checkpoint of integrity
for which gained the over name of securin. PTTG1 was found to promote malignant transformation
in 3T3 fibroblasts, and further found to be overexpressed in different tumor types. More recently,
PTTG1 has been also related to different processes such as DNA repair and found to trans-activate
different cellular pathways involving c-myc, bax or p53, among others. PTTG1 over-expression has
been correlated to a worse prognosis in thyroid, lung, colorectal cancer patients, and it can not be
excluded that this effect may also occur in other tumor types. Despite the clinical relevance and
the increasing molecular characterization of PTTG1, the reason for its up-regulation remains
unclear.
Method: We analysed PTTG1 differential expression in PC-3, DU-145 and LNCaP tumor cell
lines, cultured in the presence of the methyl-transferase inhibitor 5-Aza-2'-deoxycytidine. We also
tested whether the CpG island mapping PTTG1 proximal promoter evidenced a differential
methylation pattern in differentiated thyroid cancer biopsies concordant to their PTTG1
immunohistochemistry status. Finally, we performed whole-genome LOH studies using Affymetix
50 K microarray technology and FRET analysis to search for allelic imbalances comprising the
PTTG1 locus.
Conclusion: Our data suggest that neither methylation alterations nor LOH are involved in
PTTG1 over-expression. These data, together with those previously reported, point towards a
post-transcriptional level of missregulation associated to PTTG1 over-expression.This project was funded by The Fundación de Investigación Biomédica Mutua Madrileña Automovilista. Neocodex have been partially funded by the Ministerio de Educación y Ciencia of Spain (FIT-010000-2004-69, PTQ04-1-0006, PTQ2003-0549, PTQ2003-0546 and PTQ2003-0783). MAJ was also supported by SAF2005- 07713-C03-03 and CS by FIS 06/757