In vitro substance P-dependent induction of bone marrow cells in common (CD10) acute lymphoblastic leukaemia

The RNA-binding protein Musashi 1 stabilizes the oncotachykinin 1 mRNA in breast cancer cells to promote cell growth

Substance P and its truncated receptor exert oncogenic effects. The high production of substance P in breast cancer cells (BCCs) is caused by the enhancement of tachykinin (TAC)1 translation by cytosolic factor. In vitro translational studies and mRNA stabilization analyses indicate that BCCs contain the factor needed to increase TAC1 translation and to stabilize the mRNA. Prediction of protein folding, RNA-shift analysis, and proteomic analysis identified a 40 kDa molecule that interacts with the noncoding exon 7. Western blot analysis and RNA supershift identified Musashi 1 (Msi1) as the binding protein. Ectopic expression of TAC1 in nontumorigenic breast cells (BCs) indicates that TAC1 regulates its stability by increasing Msi1. Using a reporter gene system, we showed that Msi1 competes with microRNA (miR)130a and -206 for the 3' UTR of exon 7/TAC1. In the absence of Msi1 and miR130a and -206, reporter gene activity decreased, indicating that Msi1 expression limits TAC1 expression. Tumor growth was significantly decreased when nude BALB/c mice were injected with Msi1-knockdown BCCs. In summary, the RNA-binding protein Msi1 competes with miR130a and -206 for interaction with TAC1 mRNA, to stabilize and increase its translation. Consequently, these interactions increase tumor growth.

Expression and proliferative effect of hemokinin-1 in human B-cells

Tachykinins are a family of structurally related peptides, including substance P (SP), hemokinin-1 (HK-1), neurokinin A (NKA), and neurokinin B. SP and NKA have been shown to modulate hematopoiesis and rat/mouse HK-1 has been found to be involved in the survival and differentiation of mouse B-cells. This study was designed to assess the expression of tachykinins with a focus on human HK-1 (hHK-1) in human B lymphocytes and the role of these peptides in cell differentiation, apoptosis and proliferation. Expression of tachykinin and tachykinin receptor mRNA was determined quantitatively in human B lymphoproliferative malignancies and compared to normal B-cells. Expression of hHK-1 and NK(1) receptor, but not SP, was detected in human B-lymphocytes, and was up-regulated in B-lymphocytes from chronic lymphocytic leukemia and non-Hodgkin's lymphoma, while it was down-regulated in acute lymphoblastic leukemia. Moreover, hHK-1, in contrast to SP, was able to induce proliferation of human pre-B lymphocytes through a NK(1) receptor-independent mechanism. These data suggest a role for hHK-1 in normal and pathological B lymphopoiesis, and open the door to a better understanding of the physiopathological mechanisms leading to lymphoproliferative malignancies.

RE-1-silencing transcription factor shows tumor-suppressor functions and negatively regulates the oncogenic TAC1 in breast cancer cells

Breast cancer remains the most prevalent cancer among women in the United States. Substance P, a peptide derived from the TAC1 gene, mediates oncogenic properties in breast and other cancers. TAC1 expression facilitates the entry of breast cancer cells into bone marrow. The transcriptional repressor element 1-silencing transcription factor (REST) has been implicated in both oncogenic and tumor-suppressor functions. REST binds to the 5' untranslated region of the TAC1 promoter and suppresses its expression. This study investigated a role for REST in TAC1 induction in breast cancer. Western blots and real-time PCR indicated that REST expression in breast cancer cells was inversely proportional to the cells' aggressiveness, for both cell lines and primary breast cancer cells. REST knockdown in low-metastatic T47D cells and nontumorigenic MCF12A cells resulted in increases in TAC1 induction, proliferation, and migration. These parameters were negatively affected by ectopic expression of REST in highly aggressive MDA-MB-231 cells. Together, these findings show a central role for REST in the oncogenic function of TAC1 and suggest a tumor-suppressor role for REST in breast cancer.