There is a growing body of evidence supporting that cancer cells share many similarities with embryonic stem cells (ESCs). For example, aggressive cancers and ESCs share a common gene expression signature that includes hundreds of genes. Since ESC genes are not present in most adult tissues, they could be ideal candidate targets for cancer-specific diagnosis and treatment. This is an exciting cancer-targeting model. The major hurdle to test this model is to identify the key factors/pathway(s) within ESCs that are responsible for the cancer phenotype. SALL4 is one of few genes that can establish this link. The first publication of SALL4 is on its mutation in a human inherited disorder with multiple developmental defects. Since then, over 300 papers have been published on various aspects of this gene in stem cells, development, and cancers. This review aims to summarize our current knowledge of SALL4, including a SALL4-based approach to classify and target cancers. Many questions about this important gene still remain unanswered, specifically, on how this gene regulates cell fates at a molecular level. Understanding SALL4’s molecular functions will allow development of specific targeted approaches in the future.

Tirabrutinib is a second‐generation Bruton’s tyrosine kinase inhibitor with greater selectivity than ibrutinib. Here, we conducted a multicenter, phase II study of tirabrutinib in patients with treatment‐naïve (Cohort A) or with relapsed/refractory (Cohort B) Waldenström’s macroglobulinemia (WM). Patients were treated with tirabrutinib 480 mg once daily. The primary endpoint was major response rate (MRR; ≥ partial response). Secondary endpoints included overall response rate (ORR; ≥ minor response), time to major response (TTMR), progression‐free survival (PFS), overall survival (OS), and safety. In total, 27 patients (18 in Cohort A; 9 in Cohort B) were enrolled. The median age was 71 y, and the median serum immunoglobulin M level was 3600 mg/dL. Among the patients, 96.2% had the MYD88L265P mutation. MRR and ORR were 88.9% and 96.3%, respectively (Cohort A: MRR, 88.9%; ORR, 94.4%; Cohort B: MRR, 88.9%; ORR, 100%). Median TTMR was 1.87 mo. PFS and OS were not reached with a median follow‐up of 6.5 and 8.3 mo for Cohorts A and B, respectively. The most common adverse events (AEs) were rash (44.4%), neutropenia (25.9%), and leukopenia (22.2%), with most AEs classified as grade 1 or 2. Grade ≥ 3 AEs included neutropenia (11.1%), lymphopenia (11.1%), and leukopenia (7.4%). No grade 5 AEs were noted. All bleeding events were grade 1; none were associated with drug‐related atrial fibrillation or hypertension. Although the follow‐up duration was relatively short, the study met the primary endpoint. Therefore, tirabrutinib monotherapy is considered to be highly effective for both untreated and relapsed/refractory WM with a manageable safety profile. (JapicCTI‐173646).

Key Points• The SALL4/NuRD/PTEN pathway is important for acute myeloid leukemogenesis.• Targeting AML can be achieved by blocking the interaction between transcription factor SALL4 and the epigenetic NuRD complex.An exciting recent approach to targeting transcription factors in cancer is to block formation of oncogenic complexes. We investigated whether interfering with the interaction of the transcription factor SALL4, which is critical for leukemic cell survival, and its epigenetic partner complex represents a novel therapeutic approach. The mechanism of SALL4 in promoting leukemogenesis is at least in part mediated by its repression of the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) through its interaction with a histone deacetylase (HDAC) complex. In this study, we demonstrate that a peptide can compete with SALL4 in interacting with the HDAC complex and reverse its effect on PTEN repression. Treating SALL4-expressing malignant cells with this peptide leads to cell death that can be rescued by a PTEN inhibitor. The antileukemic effect of this peptide can be confirmed on primary human leukemia cells in culture and in vivo, and is identical to that of down-regulation of SALL4 in these cells using an RNAi approach. In summary, our results demonstrate a novel peptide that can block the specific interaction between SALL4 and its epigenetic HDAC complex in regulating its target gene, PTEN. IntroductionMembers of the SAL gene family belong to a group of C2H2 zinc finger transcription factors characterized by multiple zinc finger domains present in the protein. 1,2 Sal is a nonclustered regionspecific homeobox gene that plays an essential role in Drosophila, and Sal-related genes have been isolated from Caenorhabditis elegans, 3 fish, 4 frogs (Xenopus), 5,6 mice, 7 and humans. 2 Each of these homologs is expressed during embryonic development and in a more limited set of specific adult tissues. Murine Sall4 also plays a crucial role in development. Sall4-null mice die at embryonic day 6.5. [8][9][10][11] We have shown that murine Sall4 is essential for the maintenance of pluripotency and self-renewal properties of embryonic stem cells by interacting with 2 other key regulators, Nanog and Oct4. 11,12 After birth, SALL4 expression is down-regulated and absent in most adult tissues. However, SALL4 is expressed in various cancers, including a subset (30%) of solid tumors such as breast cancer, 13 ovarian cancer, 14 gastric cancer, 15 Wilms tumor, 16 and germ cell tumors, 14,[17][18][19][20][21] as well as in leukemias-most notably, almost all cases of human acute myeloid leukemia (AML) 22 and approximately 75% of B-cell acute lymphoblastic lymphoma/ leukemia. 23 We have also reported that SALL4 is enriched in the "side-population" of the leukemia and solid tumor cells. This side population is implicated in drug resistance and cancer initiation and is used to isolate cancer initiation cells. 24 SALL4 expression is also correlated with worse prognosis in AML patients. 24 We have also s...