Wnt/beta-catenin mediates radiation resistance of Sca1(+) progenitors in an immortalized mammary gland cell line
ABSTRACT The COMMA-Dbeta-geo cell line has been shown to contain a permanent subpopulation of progenitor cells that are enriched in outgrowth potential. Using the COMMA-Dbeta-geo cell line as a model, we sought to study the radioresistance of mammary progenitor cells. Using the putative progenitor cell marker stem cell antigen 1 (Sca1), we were able to isolate a discrete subpopulation of Sca1(+) multipotent cells from the immortalized COMMA-Dbeta-geo murine mammary cell line. At a clinically relevant dose, the Sca1(+) cells were resistant to radiation (2 Gy). Sca1(+) cells contained fewer gamma-H2AX(+) DNA damage foci following irradiation, displayed higher levels of endogenous beta-catenin, and selectively upregulated survivin after radiation. Expression of active beta-catenin enhanced self-renewal preferentially in the Sca1(+) cells, whereas suppressing beta-catenin with a dominant negative, beta-engrailed, decreased self-renewal of the Sca1(+) cells. Understanding the radioresistance of progenitor cells may be an important factor in improving the treatment of cancer. The COMMA-Dbeta-geo cell line may provide a useful model to study the signaling pathways that control mammary progenitor cell regulation.
SourceAvailable from: André O von Bueren[Show abstract] [Hide abstract]
ABSTRACT: TP53 mutations confer subgroup specific poor survival for children with medulloblastoma. We hypothesized that WNT activation which is associated with improved survival for such children abrogates TP53 related radioresistance and can be used to sensitize TP53 mutant tumors for radiation. We examined the subgroup-specific role of TP53 mutations in a cohort of 314 patients treated with radiation. TP53 wild-type or mutant human medulloblastoma cell-lines and normal neural stem cells were used to test radioresistance of TP53 mutations and the radiosensitizing effect of WNT activation on tumors and the developing brain. Children with WNT/TP53 mutant medulloblastoma had higher 5-year survival than those with SHH/TP53 mutant tumours (100% and 36.6%¿±¿8.7%, respectively (p¿<¿0.001)). Introduction of TP53 mutation into medulloblastoma cells induced radioresistance (survival fractions at 2Gy (SF2) of 89%¿±¿2% vs. 57.4%¿±¿1.8% (p¿<¿0.01)). In contrast, ß-catenin mutation sensitized TP53 mutant cells to radiation (p¿<¿0.05). Lithium, an activator of the WNT pathway, sensitized TP53 mutant medulloblastoma to radiation (SF2 of 43.5%¿±¿1.5% in lithium treated cells vs. 56.6¿±¿3% (p¿<¿0.01)) accompanied by increased number of ¿H2AX foci. Normal neural stem cells were protected from lithium induced radiation damage (SF2 of 33%¿±¿8% for lithium treated cells vs. 27%¿±¿3% for untreated controls (p¿=¿0.05). Poor survival of patients with TP53 mutant medulloblastoma may be related to radiation resistance. Since constitutive activation of the WNT pathway by lithium sensitizes TP53 mutant medulloblastoma cells and protect normal neural stem cells from radiation, this oral drug may represent an attractive novel therapy for high-risk medulloblastomas.
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ABSTRACT: Nuclear expression of β-catenin has been suggested as an independent prognostic marker in a variety of cancers. The objective of this study was to investigate the clinicopathologic significance of nuclear β-catenin expression in patients with cervical squamous cell carcinoma (CSCC). In this original research article, we detected nuclear β-catenin expression in 29/171 CSCC tissues (17.0%). Patients without nuclear β-catenin expression had a significantly better outcome than patients with nuclear β-catenin expression (93.7% versus 82.7% P = 0.027). Furthermore, nuclear β-catenin expression was predictive of prognosis in CSCC patients with early stage disease (FIGO stage I or tumor size ≤ 4 cm), with well/moderately differentiated tumors, or lymph node metastasis. Interestingly, nuclear β-catenin expression correlated with poor outcome in patients who received postoperative chemotherapy or radiotherapy. Multivariate analysis suggested that nuclear β-catenin expression is an independent prognostic indicator in CSCC. Our findings suggest that nuclear β-catenin expression may be used as a prognostic biomarker in CSCC, especially for patients with early stage disease, well/moderately differentiated tumors, or lymph node metastasis. Moreover, nuclear β-catenin expression has potential as a predictive marker of chemoresistance and radioresistance in CSCC.
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ABSTRACT: Cancer stem cells (CSCs) can avoid or efficiently repair DNA damage from radio and chemotherapy, which suggests they play a role in disease recurrence. 20% of patients treated with surgery and radiotherapy for ductal carcinoma in Situ (DCIS) of the breast recur and our previous data shows that high grade DCIS have increased numbers of CSCs. Here, we investigate the role of Focal Adhesion Kinase (FAK) and Wnt pathways in DCIS stem cells and their capacity to survive irradiation.Using DCIS cell lines and patient samples we demonstrate that CSC-enriched populations are relatively radioresistant and possess high FAK activity. Immunohistochemical studies of active FAK in DCIS tissue show high expression was associated with a shorter median time to recurrence. Treatment with a FAK inhibitor or FAK siRNA in non-adherent and 3D matrigel culture reduced mammosphere formation, and potentiated the effect of 2Gy irradiation. Moreover, inhibition of FAK in vitro and in vivo decreased self-renewal capacity, levels of Wnt3a and B-Catenin revealing a novel FAK-Wnt axis regulating DCIS stem cell activity.Overall, these data establish that the FAK-Wnt axis is a promising target to eradicate self-renewal capacity and progression of human breast cancers. Stem Cells 2014Stem Cells 09/2014; 33(2). DOI:10.1002/stem.1843 · 7.70 Impact Factor