Oncogene database

57167

SALL4

spalt-like transcription factor 4;SALL4;spalt-like transcription factor 4

sal-like protein 4|zinc finger protein 797|zinc finger protein SALL4

20q13.2

protein-coding

SALL4, a human homolog to Drosophila spalt, is a novel zinc finger transcriptional factor essential for development. We cloned SALL4 and its isoforms (SALL4A and SALL4B). Through immunohistochemistry and real-time reverse-transcription-polymerase chain reaction (RT-PCR), we demonstrated that SALL4 was constitutively expressed in human primary acute myeloid leukemia (AML, n = 81), and directly tested the leukemogenic potential of constitutive expression of SALL4 in a murine model. SALL4B transgenic mice developed myelodysplastic syndrome (MDS)-like features and subsequently AML that was transplantable. Increased apoptosis associated with dysmyelopoiesis was evident in transgenic mouse marrow and colony-formation (CFU) assays. Both isoforms could bind to beta-catenin and synergistically enhanced the Wnt/beta-catenin signaling pathway. Our data suggest that the constitutive expression of SALL4 causes MDS/AML, most likely through the Wnt/beta-catenin pathway. Our murine model provides a useful platform to study human MDS/AML transformation, as well as the Wnt/beta-catenin pathway s role in the pathogenesis of leukemia stem cells.

SALL4, a newly identified zinc-finger transcriptional factor important for embryonic development, is mapped to chromosome 20q13. Previously, we reported that SALL4 was constitutively expressed in acute myeloid leukemia and SALL4 transgenic mice developed acute myeloid leukemia. In this study, we aimed to survey SALL4 protein expression in benign and neoplastic hematopoietic tissues in addition to acute myeloid leukemia using immunostaining with a polyclonal anti-SALL4 antibody. Primary hematological tumors (178) and 15 benign hematopoietic tissues were examined. Reverse transcription-polymerase chain reaction was also performed to detect SALL4 mRNA expression on eight precursor B-cell lymphoblastic leukemia/lymphomas, 10 benign hematopoietic tissues, and seven hematopoietic cancer cell lines. Of the benign tissues, SALL4 expression was detectable only in CD34+ hematopoietic stem/progenitor cells (2/2 at protein level, 3/3 at RNA level). In neoplastic tissues, only precursor B-cell lymphoblastic leukemia/lymphomas had detectable SALL4 (12/16 at protein level, 7/8 at RNA level), similar to that observed in acute myeloid leukemia. Of the seven cell lines examined, only those derived from acute myeloid leukemia and precursor B-cell lymphoblastic leukemia/lymphomas were positive. To conclude, SALL4 expression is normally restricted to CD34+ hematopoietic stem/progenitor cells. The persistence of SALL4 expression in leukemic blasts in precursor B-cell lymphoblastic leukemia/lymphomas resembles to what we observed in acute myeloid leukemia, and correlates with the maturation arrest of these cells. We have shown in our previous study that the constitutive expression of SALL4 in mice can lead to acute myeloid leukemia development. The similar expression pattern of SALL4 in acute myeloid leukemia and B-cell lymphoblastic leukemia/lymphomas suggests that these two disease entities may share similar biological features and/or mechanisms of leukemogenesis. More definite studies to investigate the role of SALL4 in the pathogenesis of B-cell lymphoblastic leukemia/lymphomas are needed in the future to address this question.

Myelodysplastic syndromes (MDS) are a group of heterogeneous clonal stem cell diseases with a tendency to progress to leukemic transformation. The cytogenetic and molecular pathogenesis of MDS has not been well understood. SALL4, a newly identified oncogene, modulates stem cell pluripotency and self-renewal capability in embryonic development and also plays a role in leukemogenesis. Overexpression of SALL4 induces MDS-like features and subsequent leukemic progression in transgenic mice. Here, we examined SALL4 expression levels in bone marrow mononuclear cells from MDS patients, acute myeloid leukemia (AML) patients, and normal control subjects using a semiquantitative reverse transcription polymerase chain reaction. Higher levels of SALL4 expression were seen in MDS and AML samples than in control samples. The expression level of SALL4 positively correlated with those of MYC and CCND1, both of which are downstream target genes in the Wnt/beta-catenin pathway. We therefore propose that SALL4 plays a critical role in the pathogenesis of MDS by causing the aberrant activation of the Wnt/beta-catenin pathway.

SALL4 is one of the master transcriptional factors that are crucial in maintaining the pluripotency of embryonic stem cells (ESCs). While the expression of SALL4 is normally restricted to ESCs and somatic stem cells, we found that it is aberrantly expressed in ALK-positive anaplastic large cell lymphoma (ALK+ ALCL), a type of lymphoid malignancy carrying a mature T-cell immunophenotype. shRNA knockdown of SALL4 in ALK+ ALCL cell lines resulted in apoptosis and cell-cycle arrest, and significantly decreased colony formation on soft agar. These changes correlated with the downregulation of several anti-apoptotic proteins and facilitators of cell-cycle progression. Based on the differential response to a SALL4 reporter construct, we were able to separate two distinct cell subsets in Karpas 299 (an ALK+ ALCL cell line), namely SALL4(high) and SALL4(low). Importantly, the biological effects induced by SALL4 knock-down in Karpas 299 were restricted to the purified SALL4(high) cells, and this finding further supports the concept that SALL4 is biologically important in ALK+ ALCL. Lastly, the expression of SALL4 was not dependent on the nucleophosmin (NPM)-anaplastic lymphoma kinase (ALK)/STAT3 signaling axis, the key oncogenic driver in ALK+ ALCL. To conclude, for the first time, our study has revealed the oncogenic contributions of an ESC protein in the pathogenesis of ALK+ ALCL.

Sall4 is a novel oncogene found upregulated in several malignancies including colon cancer. However, its upstream regulatory miRNA is still undefined. miR-219-5p is regarded as a tumor-related miRNA in cancer research. Nevertheless, its actual role of whether inhibiting or promoting tumorigenesis is unclear in colon cancer. Potential interaction between Sall4 and miR-219-5p is predicted by TargetScan. CCK-8 test was used for evaluation of cell proliferation and cell survival rates. Western blot analysis and real-time PCR were applied for detection of target molecules. Luciferase assay was a direct confirmation of mutual interaction. Wound healing assay and transwell assay were conducted for cell migration and invasion tests. Flow cytometry was used for cell apoptosis analysis. Tissue specimens and cell lines were explored for miR-219-5p inhibition on colon cancer proliferation, migration, invasion, apoptosis and drug resistance by targeting Sall4. The results show that miR-219-5p inhibited carcinogenesis of colon cancer by targeting oncogene Sall4.