Knock-down of Kaiso induces proliferation and blocks granulocytic differentiation in blast crisis of chronic myeloid leukemia

Abstract

BackgroundKaiso protein has been identified as a new member of the POZ-ZF subfamily of transcription factors that are involved in development and cancer. There is consistent evidence of the role of Kaiso and its involvement in human tumorigenesis but there is no evidence about its role in hematopoietic differentiation or establishment of chronic myeloid leukemia (CML). We used, normal K562 cell line, established from a CML patient in blast crisis, and imatinib-resistant K562 cell line, to investigate the specific distribution of Kaiso and their contribution to the cell differentiation status of the blast crisis of CML (CML-BP).ResultsWe found cytoplasmic expression of Kaiso, in K562 cells and patients, confirmed by immunofluorescence, immunohistochemistry and western blot of cytoplasmic protein fraction. Kaiso was weakly expressed in the imatinib-resistant K562 cell line confirmed by immunofluorescence and western blot. The cytoplasmic expression of Kaiso was not modified when the K562 cells were treated for 16 h with imatinib 0.1 and 1 μM. In our study, small interfering RNA (siRNA) was introduced to down regulate the expression of Kaiso and p120ctn in K562 cell line. Kaiso and p120ctn were down regulated individually (siRNA-Kaiso or siRNA-p120ctn) or in combination using a simultaneous co-transfection (siRNA-Kaiso/p120ctn). We next investigated whether knockdown either Kaiso or p120ctn alone or in combination affects the cell differentiation status in K562 cells. After down regulation we analyzed the expression of hematopoietic cell differentiation and proliferation genes: SCF, PU-1, c-MyB, C/EBPα, Gata-2 and maturation markers of hematopoietic cells expressed in the plasma membrane: CD15, CD11b, CD33, CD117. The levels of SCF and c-MyB were increased by 1000% and 65% respectively and PU-1, Gata-2 and C/EBPα were decreased by 66%, 50% and 80% respectively, when Kaiso levels were down regulated by siRNA. The results were similar when both Kaiso and p120ctn were down regulated by siRNA. The increased expression of SCF and decreased expression of GATA-2 could be responsible by the higher cell viability detected in K562 cells double knock-down of both Kaiso and p120ctn. Finally, we studied the effect of knock-down either Kaiso or p120ctn, alone or in combination on CD15, CD11b, CD33 and Cd117 expression. Using siRNA approach a reduction of 35%, 8% and 13% in CD15, CD33 and CD117 levels respectively, were achieved in all transfections, when compared to scrambled knock-down cells.ConclusionThese results suggest that both Kaiso and p120ctn, contributes to maintaining the differentiated state of the K562 cells and similar to other cancers, cytoplasmic localization of Kaiso is related to a poor prognosis in CML-BP. By the broad and profound effects on the expression of genes and markers of hematopoietic differentiation produced by Kaiso knock-down, these findings reveal Kaiso as a potential target for selective therapy of CML.

A feedback loop that regulates the expression of polycomb group protein Suz12 via non-canonical WNT signaling pathway in blast crisis of chronic myeloid leukemia

“…As it was previously reported, the RNAi knock-down of Kaiso in K562 cells improves survival and proliferation [3]. On the other hand, we know that the expression of Suz12 is significantly increased in various types of cancer [15].…”

“…Some changes in the regulatory loop may produce significant consequences for the development, for example, of chronic myeloid leukemia as the subcellular localization of Kaiso is susceptible to microenvironmental alterations of the cell [17]. Thus, we imagine that Kaiso's displacement from the nucleus to the cytoplasmic compartment [3], thereby breaking the normal regulatory loop equilibrium could be responsible for triggering the super expression of Wnt5a/Wnt11, and consequently, the overexpression of Suz12 in the context of that cell set. Consistent with the rupture of regulatory loop equilibrium the PcG proteins overexpression seems to be a trademark for some types of tumors [5,6,9,10,20].…”

Nuclear localization of Kaiso promotes the poorly differentiated phenotype and EMT in infiltrating ductal carcinomas

“…Kaiso is expressed in numerous tumor types, with different subcellular patterns. For example, elevated levels of Kaiso are present in the cytoplasm of chronic leukemia cells and in cells of non-small cell lung cancers in late stages [13, 14]. In colorectal and prostate cancers, however, Kaiso is present in both the cytoplasm and the nucleus, with more expression within the nuclear compartment [15, 16].…”

Kaiso overexpression promotes intestinal inflammation and potentiates intestinal tumorigenesis in ApcMin/+ mice

“…These findings suggested 25 that Kaiso potentiates intestinal tumorigenesis, but this was paradoxical as Kaiso was previously implicated as 26 a negative regulator of Wnt/β-catenin signaling. To resolve Kaiso's role in intestinal tumorigenesis and canonical 27 Wnt signaling, we generated a transgenic mouse model (Kaiso Tg/+ ) expressing an intestinal-specific myc-tagged 28 Kaiso transgene. We then mated Kaiso Tg/+ and Apc Min/+ mice to generate Kaiso Tg/+ :Apc Min/+ mice for further 29 characterization.…”

“…Since the Kaiso binding partner p120 ctn has been implicated as Kaiso has been implicated in the development and progression of 444 several human cancers, including colorectal cancer [5,9,11,22,[28][29][30][31][32][33][34]. that certain effects arising from Kaiso depletion models may be masked …”