Forced expression of Wnt antagonists sFRP1 and WIF1 sensitizes chronic myeloid leukemia cells to tyrosine kinase inhibitors

Chronic myeloid leukemia is a clonal myeloproliferative disorder that arises from the neoplastic transformation of the hematopoietic stem cell, in which the Wnt/β-catenin signaling pathway has been demonstrated to play an important role in disease progression. However, the role of Wnt signaling antagonists in therapy resistance and disease progression has not been fully investigated. We aimed to study the effects of Wnt/β-catenin pathway antagonists—secreted frizzled-related protein 1 and Wnt inhibitory factor 1—on resistance toward tyrosine kinase inhibitors in chronic myeloid leukemia. Response to tyrosine kinase inhibitors was analyzed in secreted frizzled-related protein 1 and Wnt inhibitory factor 1 stably transfected K562 cells. Experiments were repeated using a tetracycline-inducible expression system, confirming previous results. In addition, response to tyrosine kinase inhibitor treatment was also analyzed using the secreted frizzled-related protein 1 expressing, BCR-ABL positive MEG01 cell line, in the presence and absence of a secreted frizzled-related protein 1 inhibitor. Our data suggests that total cellular β-catenin levels decrease in the presence of secreted frizzled-related protein 1 and Wnt inhibitory factor 1, and a significant increase in cell death after tyrosine kinase inhibitor treatment is observed. On the contrary, when secreted frizzled-related protein 1 is suppressed, total β-catenin levels increase in the cell and the cells become resistant to tyrosine kinase inhibitors. We suggest that Wnt antagonists carry the potential to be exploited in designing new agents and strategies for the advanced and resistant forms of chronic myeloid leukemia.

An analysis of polymorphisms within the Wnt signaling pathway in relation to ovarian cancer risk in a Polish population

Background and Objective

The Wnt/β-catenin signaling pathway has been considered to be a factor in the development and progression of ovarian cancer.

Methods

All patients with ovarian cancer and controls were tested for BRCA1 mutations (5382incC, C61G, 4153delA) with HybProbe assays and for BRCA2 mutation (5946delT) using high-resolution melting curve analysis (HRM). Mutation carriers were excluded from the association analysis. We studied nine single nucleotide polymorphisms (SNPs) located in CTNNB1 (β-catenin) [rs4533622, rs2953], APC (rs11954856, rs351771, rs459552), and AXIN2 (rs4074947, rs7224837, rs3923087, rs2240308) in women with ovarian cancer without BRCA1/BRCA2 mutations (n = 228) and controls (n = 282). Genotyping of CTNNB1 rs4533622, rs2953, APC rs351771, AXIN2 rs4074947, rs3923087, and rs2240308 was performed by HRM, while that of APC rs11954856, rs459552 and AXIN2 rs7224837 was conducted by PCR followed by the appropriate restriction enzyme digestion [PCR–restriction fragment length polymorphism (PCR-RFLP)].

Results

The most common BRCA1/BRCA2 mutations were identified in 30 patients with ovarian cancer. These mutations were not found in controls. The lowest p values of the trend test (p_trend) were observed for the APC rs351771 and rs11954856 SNPs in patients with ovarian cancer (p_trend = 0.006 and p_trend = 0.007, respectively). Using a dominant inheritance model, we found that the APC rs11954856 SNP is associated with an increased risk of ovarian cancer development [odds ratio = 2.034 (95 % CI 1.302–3.178); p = 0.002]. We also observed significant allelic differences for the APC rs351771 SNP between patients and controls (p = 0.006).

Conclusion

Our study demonstrated significantly increased APC rs11954856 and rs351771 SNP frequencies in Polish women with ovarian cancer.

Electronic supplementary material

The online version of this article (doi:10.1007/s40291-013-0059-y) contains supplementary material, which is available to authorized users.

Two anatomically distinct niches regulate stem cell activity

The niche microenvironment controls stem cell number, fate, and behavior. The bone marrow, intestine, and skin are organs with highly regenerative potential, and all produce a large number of mature cells daily. Here, focusing on adult stem cells in these organs, we compare the structures and cellular components of their niches and the factors they produce. We then define the niche as a functional unit for stem cell regulation. For example, the niche possibly maintains quiescence and regulates fate in stem cells. Moreover, we discuss our hypothesis that many stem cell types are regulated by both specialized and nonspecialized niches, although hematopoietic stem cells, as an exception, are regulated by a nonspecialized niche only. The specialized niche is composed of 1 or a few types of cells lying on the basement membrane in the epithelium. The nonspecialized niche is composed of various types of cells widely distributed in mesenchymal tissues. We propose that the specialized niche plays a role in local regulation of stem cells, whereas the nonspecialized niche plays a role in relatively broad regional or systemic regulation. Further work will verify this dual-niche model to understand mechanisms underlying stem cell regulation.

Normal hematopoiesis and hematologic malignancies: role of canonical Wnt signaling pathway and stromal microenvironment

Wnts are a family of evolutionary-conserved secreted signaling molecules critically involved in a variety of developmental processes and in cell fate determination. A growing body of evidence suggests that Wnt signaling plays a crucial role in the influence of bone marrow stromal microenvironment on the balance between hematopoietic stem cell self-renewal and differentiation. Emerging clinical and experimental evidence also indicates Wnt signaling involvement in the disruption of the latter balance in hematologic malignancies, where the stromal microenvironment favors the homing of cancer cells to the bone marrow, as well as leukemia stem cell development and chemoresistance. In the present review, we summarize and discuss the role of the canonical Wnt signaling pathway in normal hematopoiesis and hematologic malignancies, with regard to recent findings on the stromal microenvironment involvement in these process and diseases.

Role of Wnt canonical pathway in hematological malignancies

Wnt canonical signaling pathway plays a diverse role in embryonic development and maintenance of organs and tissues in adults. It has been observed that Wnt/β-catenin signaling pathway is involved in the pathogenesis of many carcinomas. Moreover, Wnt/β-catenin pathway has been revealed to be associated with angiogenesis. Wnt canonical pathway signaling has great potential as a therapeutic target. It has been disclosed that some hematological malignancies, such as chronic lymphocytic leukemia, mantle cell lymphoma, may occur partly due to the constitutive activation of Wnt canonical signaling pathway. This review will summarize the latest development in Wnt canonical signaling pathway and its roles in tumorigenesis and angiogenesis.