TCF4 promotes erythroid development.

Transcription factor 4 (TCF4) is implicated in lymphoid cell differentiation and its expression predicts outcome in acute myeloid leukemia. Here, we investigated the role of TCF4 in myelopoiesis. Overexpression of TCF4 (TCF4OE) in umbilical cord blood (UCB) cells resulted in a twofold increase in erythroid colony forming units (CFU-Es), whereas knock-down (KD) of TCF4 (TCF4KD) caused a dramatic decrease in the number of erythroid colonies. In megakaryocyte CFUs (CFU-MKs), both TCF4KD and TCF4OE inhibited MK colony formation. TCF4 did not have an impact on granulocyte, macrophage, or granulocyte-macrophage colonies or on the proportion of MK-erythrocyte progenitors (MEPs) in culture. Because TCF4 affects erythroid/MK development and these lineages are affected in myelodysplastic syndrome (MDS), we studied the impact of TCF4 expression in this disease. MDS patients with high (≥median) TCF4 mRNA expression had higher hemoglobin (Hb) levels than MDS patients with low TCF4 expression (mean 9.0 vs. 8.55 g/dL, p = 0.02). Overall, TCF4 mRNA expression was lower in hematopoietic stem cells, common myeloid progenitors, and MEPs from MDS patients, but not in granulocyte-macrophage progenitors, compared with healthy controls. Therefore, in cell fractions with erythroid lineage potential, TCF4 is expressed less in MDS patients than in healthy controls. This correlates with the low overall Hb levels seen in MDS patients compared with healthy individuals and is consistent with the positive impact of TCF4 on erythroid development while not having impact on white colonies. These results indicate a role for TCF4 as a novel factor in erythroid-megakaryocytic differentiation.

Apoptosis-Related Gene Expression Profiling in Hematopoietic Cell Fractions of MDS Patients.

Although the vast majority of patients with a myelodysplastic syndrome (MDS) suffer from cytopenias, the bone marrow is usually normocellular or hypercellular. Apoptosis of hematopoietic cells in the bone marrow has been implicated in this phenomenon. However, in MDS it remains only partially elucidated which genes are involved in this process and which hematopoietic cells are mainly affected. We employed sensitive real-time PCR technology to study 93 apoptosis-related genes and gene families in sorted immature CD34+ and the differentiating erythroid (CD71+) and monomyeloid (CD13/33+) bone marrow cells. Unsupervised cluster analysis of the expression signature readily distinguished the different cellular bone marrow fractions (CD34+, CD71+ and CD13/33+) from each other, but did not discriminate patients from healthy controls. When individual genes were regarded, several were found to be differentially expressed between patients and controls. Particularly, strong over-expression of BIK (BCL2-interacting killer) was observed in erythroid progenitor cells of low- and high-risk MDS patients (both p = 0.001) and TNFRSF4 (tumor necrosis factor receptor superfamily 4) was down-regulated in immature hematopoietic cells (p = 0.0023) of low-risk MDS patients compared to healthy bone marrow.

Aging impairs long-term hematopoietic regeneration after autologous stem cell transplantation.

Most of our knowledge of the effects of aging on the hematopoietic system comes from studies in animal models. In this study, to explore potential effects of aging on human hematopoietic stem and progenitor cells (HSPCs), we evaluated CD34(+) cells derived from young (<35 years) and old (>60 years) adult bone marrow with respect to phenotype and in vitro function. We observed an increased frequency of phenotypically defined stem and progenitor cells with age, but no distinct differences with respect to in vitro functional capacity. Given that regeneration of peripheral blood counts can serve as a functional readout of HSPCs, we compared various peripheral blood parameters between younger patients (≤50 years; n = 64) and older patients (≥60 years; n = 55) after autologous stem cell transplantation. Patient age did not affect the number of apheresis cycles or the amount of CD34(+) cells harvested. Parameters for short-term regeneration did not differ significantly between the younger and older patients; however, complete recovery of all 3 blood lineages at 1 year after transplantation was strongly affected by advanced age, occurring in only 29% of the older patients, compared with 56% of the younger patients (P = .009). Collectively, these data suggest that aging has only limited effects on CD34(+) HSPCs under steady-state conditions, but can be important under consitions of chemotoxic and replicative stress.

Novel transcriptional targets of the SRY-HMG box transcription factor SOX4 link its expression to the development of small cell lung cancer.

The HMG box transcription factor SOX4 involved in neuronal development is amplified and overexpressed in a subset of lung cancers, suggesting that it may be a driver oncogene. In this study, we sought to develop this hypothesis including by defining targets of SOX4 that may mediate its involvement in lung cancer. Ablating SOX4 expression in SOX4-amplified lung cancer cells revealed a gene expression signature that included genes involved in neuronal development such as PCDHB, MYB, RBP1, and TEAD2. Direct recruitment of SOX4 to gene promoters was associated with their upregulation upon ectopic overexpression of SOX4. We confirmed upregulation of the SOX4 expression signature in a panel of primary lung tumors, validating their specific response by a comparison using embryonic fibroblasts from Sox4-deficient mice. Interestingly, we found that small cell lung cancer (SCLC), a subtype of lung cancer with neuroendocrine characteristics, was generally characterized by high levels of SOX2, SOX4, and SOX11 along with the SOX4-specific gene expression signature identified. Taken together, our findings identify a functional role for SOX genes in SCLC, particularly for SOX4 and several novel targets defined in this study.