RESUMO
Sporadic colorectal cancer (CRC) insurgence and progression depend on the activation of Wnt/ß-catenin signaling. Dickkopf (DKK)-1 is an extracellular inhibitor of Wnt/ß-catenin signaling that also has undefined ß-catenin-independent actions. Here we report for the first time that a proportion of DKK-1 locates within the nucleus of healthy small intestine and colon mucosa, and of CRC cells at specific chromatin sites of active transcription. Moreover, we show that DKK-1 regulates several cancer-related genes including the cancer stem cell marker aldehyde dehydrogenase 1A1 (ALDH1A1) and Ral-binding protein 1-associated Eps domain-containing 2 (REPS2), which are involved in detoxification of chemotherapeutic agents. Nuclear DKK-1 expression is lost along CRC progression; however, it remains high in a subset (15%) of CRC patients (n = 699) and associates with decreased progression-free survival (PFS) after chemotherapy administration and overall survival (OS) [adjusted HR, 1.65; 95% confidence interval (CI), 1.23-2.21; P = 0.002)]. Overexpression of ALDH1A1 and REPS2 associates with nuclear DKK-1 expression in tumors and correlates with decreased OS (P = 0.001 and 0.014) and PFS. In summary, our findings demonstrate a novel location of DKK-1 within the cell nucleus and support a role of nuclear DKK-1 as a predictive biomarker of chemoresistance in colorectal cancer.
Assuntos
Biomarcadores Tumorais/metabolismo , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Aldeído Desidrogenase/biossíntese , Aldeído Desidrogenase/genética , Família Aldeído Desidrogenase 1 , Biomarcadores Tumorais/biossíntese , Biomarcadores Tumorais/genética , Proteínas de Ligação ao Cálcio , Linhagem Celular Tumoral , Núcleo Celular/metabolismo , Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Resistencia a Medicamentos Antineoplásicos , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/genética , Mucosa Intestinal/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/biossíntese , Peptídeos e Proteínas de Sinalização Intracelular/genética , Masculino , Prognóstico , Retinal Desidrogenase , Transdução de SinaisRESUMO
Protein phosphatase 2A (PP2A) is a tumor suppressor that regulates many signaling pathways crucial for cell transformation. In fact, decreased activity of PP2A has been reported as a recurrent alteration in many types of cancer. Here, we show that PP2A is frequently inactivated in patients with colorectal cancer, indicating that PP2A represents a potential therapeutic target for this disease. We identified overexpression of the endogenous PP2A inhibitors SET and CIP2A, and downregulation of regulatory PP2A such as PPP2R2A and PPP2R5E, as contributing mechanisms to PP2A inhibition in colorectal cancer. Moreover, we observed that its restoration using FTY720 impairs proliferation and clonogenic potential of colorectal cancer cells, induces caspase-dependent apoptosis, and affects AKT and extracellular signal-regulated kinase-1/2 activation status. Interestingly, treatment with FTY720 showed an additive effect with 5-fluorouracil, SN-38, and oxaliplatin, drugs used in standard chemotherapy in patients with colorectal cancer. These results suggest that PP2A activity is commonly decreased in colorectal cancer cells, and that the use of PP2A activators, such as FTY720, might represent a potential novel therapeutic strategy in colorectal cancer.
