Project description:Protein inhibitor of activated STAT3 (PIAS3) is an endogenous inhibitor of STAT3 that negatively regulates STAT3 transcriptional activity and cell growth and demonstrates limited expression in the majority of human squamous cell carcinomas of the lung. In the present study we sought to determine if PIAS3 inhibits cell growth in non-small cell lung cancer (NSCLC) cell lines by induction of apoptosis and further determine the dependence of PIAS3 activity on p53 status by using both wild-type and p53-null cells. Our results demonstrate that over-expression of PIAS3 promotes caspase 3 activation and PARP cleavage. Furthermore, the expression of pro-survival family members Bcl-xL and Bcl-2 is decreased. These effects were observed after both transient and regulated expression of exogenous PIAS3 and were independent of p53 status. Furthermore, while p53 can promote apoptosis by inhibition of STAT3 activity, PIAS3 inhibition of STAT3 activity was also p53 independent. Microarray experiments were performed to further investigate the STAT3-dependence of PIAS3-induced apoptosis by comparing the apoptotic gene expression signature induced by PIAS3 over-expression with that induced by STAT3 siRNA. The results showed that a subset of apoptotic genes, including CIDEC and DAPK2, were uniquely expressed only after PIAS3 expression. Thus, PIAS3 may represent a promising lung cancer therapeutic target because of its p53-independent efficacy as well as its potential to synergize with direct STAT3 inhibitors. The expression profiles of genes related to apoptosis in A549 cell line transfected with pCMV5 vector encoding human PIAS3 compared with that induced by STAT3 siRNA Cells in all three groups were grown in serum-free medium, then stimulated with EGF, then one group transfected with pCMV5 vector encoding human PIAS3, second group was induced by STAT3 siRNA, third group considered as control.
Project description:Protein inhibitor of activated STAT3 (PIAS3) is an endogenous inhibitor of STAT3 that negatively regulates STAT3 transcriptional activity and cell growth and demonstrates limited expression in the majority of human squamous cell carcinomas of the lung. In the present study we sought to determine if PIAS3 inhibits cell growth in non-small cell lung cancer (NSCLC) cell lines by induction of apoptosis and further determine the dependence of PIAS3 activity on p53 status by using both wild-type and p53-null cells. Our results demonstrate that over-expression of PIAS3 promotes caspase 3 activation and PARP cleavage. Furthermore, the expression of pro-survival family members Bcl-xL and Bcl-2 is decreased. These effects were observed after both transient and regulated expression of exogenous PIAS3 and were independent of p53 status. Furthermore, while p53 can promote apoptosis by inhibition of STAT3 activity, PIAS3 inhibition of STAT3 activity was also p53 independent. Microarray experiments were performed to further investigate the STAT3-dependence of PIAS3-induced apoptosis by comparing the apoptotic gene expression signature induced by PIAS3 over-expression with that induced by STAT3 siRNA. The results showed that a subset of apoptotic genes, including CIDEC and DAPK2, were uniquely expressed only after PIAS3 expression. Thus, PIAS3 may represent a promising lung cancer therapeutic target because of its p53-independent efficacy as well as its potential to synergize with direct STAT3 inhibitors.
Project description:Oncogenic STAT3 functions are known in various malignancies. We found that STAT3 plays an unexpected tumor suppressive role in KRAS-mutant non-small-cell-lung cancer (NSCLC). In mice, tissue-specific inactivation of Stat3 resulted in increased Kras (G12D)-driven NSCLC initiation and malignant progression leading to markedly reduced survival. Clinically, low STAT3 expression levels correlate with poor survival in human lung adenocarcinoma patients with smoking history. Consistently, KRAS-mutant lung tumors showed reduced STAT3 levels. Mechanistically, we show that STAT3 controls NFκB-induced IL-8-expression by sequestering NFκB in the cytoplasm while IL-8 in turn regulates myeloid tumor infiltration and tumor vascularization thereby promoting tumor progression. These results identify a novel STAT3-NFκB-IL-8 axis in KRAS-mutant NSCLC with therapeutic and prognostic relevance WT: Control lung; KRAS: Lung tumors expressing KRAS G12D; KRAS STAT3 KO: Lung tumors expressing KRAS G12D- STAT3 deficient; tumors of four mice pooled per sample
Project description:Recent evidence suggests that non-coding RNAs play an integral regulatory role in numerous functions in lung cancer development. Here, we report identification of a novel lncRNA, herein termed TP53-inhibiting lncRNA (TILR), which plays a role as a constitutive negative regulator of p53 expression and hence its functions including activation of downstream genes such as p21 and MDM2 and induction of apoptosis. Proteomic search for TILR-associated protein revealed the association with PCBP2, and the mid-portion of TILR was required for both PCBP2 and p53 mRNA binding. In addition, depletion of PCBP2 faithfully phenocopied effects of TILR silencing. We also found that TILR suppressed p53 expression post-transcriptionally as well as via a positive feedback loop between p53 and the Fanconi anemia pathway genes. Taken together, our findings clearly demonstrate that TILR constitutively inhibits p53 expression in cooperation with PCBP2, maintaining p53 transcriptional activity at a level sufficiently low for avoidance of spurious apoptosis induction.
Project description:Recent evidence suggests that non-coding RNAs play an integral regulatory role in numerous functions in lung cancer development. Here, we report identification of a novel lncRNA, herein termed TP53-inhibiting lncRNA (TILR), which plays a role as a constitutive negative regulator of p53 expression and hence its functions including activation of downstream genes such as p21 and MDM2 and induction of apoptosis. Proteomic search for TILR-associated protein revealed the association with PCBP2, and the mid-portion of TILR was required for both PCBP2 and p53 mRNA binding. In addition, depletion of PCBP2 faithfully phenocopied effects of TILR silencing. We also found that TILR suppressed p53 expression post-transcriptionally as well as via a positive feedback loop between p53 and the Fanconi anemia pathway genes. Taken together, our findings clearly demonstrate that TILR constitutively inhibits p53 expression in cooperation with PCBP2, maintaining p53 transcriptional activity at a level sufficiently low for avoidance of spurious apoptosis induction.
Project description:To define the impact of STAT3-deletion on gene expresssion in primary and metastatic small cell lung cancer Gene expression was defined for cell lines derived from primary or liver metastases from independent mice by RNA-Seq
Project description:Here, we examined the role of intestinal epithelial specific tumor suppressive function of 53. We provide evidence that p53 plays a dual role during carcinogen-induced tumorigenesis. At the initiation stage, p53 controls DNA damage and survival of initiated epithelia. In contrast, at later stages, loss of p53 is associated with the formation of an inflammatory microenvironment that is linked to epithelial mesenchymal transition, invasion and metastasis and the activation of NF-kappaB and Stat3. Thus, we propose a novel p53 controlled tumor suppressive function during the progression stage of colorectal cancer that is independent of its well-established role in cell cycle regulation, apoptosis and senescence. 6 samples were analyzed. We compared 3 wt colon tumor samples and 3 p53-knockout tumor samples.
Project description:Loss of p53 is considered to allow progression of colorectal tumors from the adenoma to the carcinoma stage. Using mice with an intestinal epithelial cell (IEC) specific deletion of p53, we demonstrate that single loss of p53 is not sufficient to initiate intestinal tumorigenesis, but markedly enhances carcinogen-induced tumor incidence and leads to invasive cancer and lymph node metastasis. While during the initiation stage p53 controls DNA damage and IEC survival, during tumor progression, loss of p53 is associated with the formation of an inflammatory microenvironment and activation of NF-kB and Stat3. Thus, we propose a novel p53 controlled tumor suppressive function that is independent of its well-established role in cell cycle regulation, apoptosis and senescence.
Project description:Here, we examined the role of intestinal epithelial specific tumor suppressive function of 53. We provide evidence that p53 plays a dual role during carcinogen-induced tumorigenesis. At the initiation stage, p53 controls DNA damage and survival of initiated epithelia. In contrast, at later stages, loss of p53 is associated with the formation of an inflammatory microenvironment that is linked to epithelial mesenchymal transition, invasion and metastasis and the activation of NF-kappaB and Stat3. Thus, we propose a novel p53 controlled tumor suppressive function during the progression stage of colorectal cancer that is independent of its well-established role in cell cycle regulation, apoptosis and senescence.
Project description:We report the gene expression profiles by NGFR knockdown in H460 and H1299 cell lines and reveal that NGFR ablation activates p53 target gene expression. We examined gene expression in two different non-small-cell lung cancer cell lines, one with wild-type p53 and the other without p53.