Expression and intracellular localization of ACA and TRA-1-81 in smooth muscle cell tumors.

We studied the expression and intracellular localization of ACA and TRA-1-81 in smooth muscle cell tumors. The study was performed on tissue specimens obtained during surgery from patients with uterine leiomyoma and leiomyosarcoma (mean age 34 and 51 years, respectively). ACA was present in leiomyoma, leiomyosarcoma, and control myometrium. Intracellular expression of ACA varied in different types of tumors and was minimum in normal myometrium and maximum in leiomyosarcoma. Membrane localization of the protein is typical of common and cellular leiomyoma, while in the growth zones of mitotically active leiomyoma and leiomyosarcoma the reaction product was primarily located in tumor cell cytoplasm. TRA was detected in some leiomyosarcoma cells. Thus, ACA dysregulation was revealed in the growth zones of leiomyomas and in leiomyosarcomas, which manifested in enhanced expression of this protein and its detachment from the plasma membrane, which leads ACA translocation into the cytoplasm and nucleus of tumor cells and potentiates their proliferative activity.

A novel human glycoprotein ACA is an upstream regulator of human hematopoiesis.

A central issue in stem cell biology is a better understanding of the molecular mechanisms that regulate self-renewal of human hematopoietic stem cells (HSCs). Control of the specific function of HSCs like self-renewal and differentiation might be regulated by a common set of critical genes. However, the regulation among these genes is yet to be elucidated. Here, we show that activation by a novel human GPI-linked glycoprotein ACA at the surface of human peripheral blood progenitor cells induces via PI3K/Akt/mTor/PTEN upregulation of WNT, Notch1, Bmi-1 and HoxB4 genes thus, promoting self-renewal and generation of primitive HSCs. ACA-generated self-renewing cells retained their lympho-myeloid repopulating potential in NOD/SCID mouse xeno-transplantation model with long term functional capacity. We conclude that ACA is an essential regulator of the genes involved in maintaining hematopoiesis and its use in clinical praxis could overcome many of the barriers present so far in transplantation medicine.

Activation by ACA induces pluripotency in human blood progenitor cells.

Reprogramming of human somatic cells by transcription factors to pluripotent state holds great promise for regenerative medicine. However, low efficiencies of current reprogramming methods, immunogenicity and lack of understanding regarding the molecular mechanisms responsible for their generation, limits their utilization and raises questions regarding safety for therapeutic application. Here we report that ACA signaling via PI3K/Akt/mTor induces sustained de-differentiation of human blood progenitor cells leading to generation of ACA pluripotent stem cells. Blood-derived pluripotent stem cells differentiate in vitro into cell types of all three germ layers, exhibiting neuronal, liver, or endothelial characteristics. Our results reveal insight into the molecular events regulating cellular reprogramming and also indicate that pluripotency might be controlled in vivo through binding of a natural ligand(s) to ACA receptor enabling reprogramming through defined pathway(s) and providing a safe and efficient method for generation of pluripotent stem cells which could be a breakthrough in human therapeutics.