ALBERT

Description: CBFβ-SMMHC, encoded by the inv(16) or t(16;16) translocations in approximately 8% of acute myeloid leukemia (AML) cases, is a fusion protein containing amino acids 1-165 of the 182 residue core binding factor β (CBFβ) and the rod domain of smooth muscle myosin heavy chain (SMMHC). The CBFβ domain of CBFβ-SMMHC retains the ability to interact with AML1/RUNX1. The SMMHC domain both mediates multimerization and interacts directly with corepressors, including mSin3A. CBFβ-SMMHC inhibits the expression of AML1-regulated genes, by sequestering AML1 in multimeric complexes and by directly repressing AML1-regulated genes. CBFβ-SMMHC was previously found to slow G1 to S cell cycle progression in hematopoietic cell lines, reflecting repression of AML1-regulated genes required for cell cycle, including cyclin D3. This effect was overcome be exogenous c-Myc or cdk4. In this study, murine marrow or human CD34+ cells were transduced with retroviral or lentiviral vectors, respectively, expressing CBFβ-SMMHC or two mutant variants. CBFβ-SMMHC reduced murine or human myeloid cell proliferation 3- to 4-fold in liquid culture, during a period when control murine cells accumulated 5-fold and human cells 20-fold. CBFβ-SMMHC decreased the formation of myeloid, but not erythroid, colonies 2- to 4-fold, and myeloid colonies expressing CBFβ-SMMHC were markedly reduced in size. Lack of effect on erythroid colonies reflects their lack of expression of AML1. The mutant variant CBFβ-SMMHC(Δ2-11) does not bind AML1 due to a deletion near its N-terminus, and CBFβ-SMMHC(ΔACD) does not multimerize or efficiently bind corepressors due to a 28 residue deletion near its C-terminus. Neither of these mutants, which were expressed at levels similar to wild-type, slowed proliferation or reduced myeloid colonies. CBFβ-SMMHC increased the G1/S ratio in wild-type murine and human progenitors. Proliferation was still slowed in p15(−/−) murine marrow cells transduced with CBFβ-SMMHC, suggesting that additional mutations, such as activation of growth factor receptors and consequent c-myc induction, are required in primary AMLs to allow enhanced proliferation. AML1-ER(T), which contains full-length AML1 and accelerates G1 to S progression in cell lines when activated by 4HT, had an effect opposite to CBFβ-SMMHC, stimulating proliferation of murine or human myeloid progenitors 2-fold. In summary, CBFβ-SMMHC inhibits the proliferation of myeloid progenitors dependent upon inhibition of AML1 and integrity of its Assembly Competence Domain. Targeting the CBFβ-SMMHC ACD or its CBFβ domain may uncover novel therapeutics useful for AML cases expressing this oncoprotein. Furthermore, these findings support a model we have proposed previously which states that mutations which accelerate G1 are required during leukemogenesis by CBFβ-SMMHC and other CBF oncoproteins. Finally, our results lend support to the conclusion that AML1 participates in the regulation of normal myeloid stem-progenitor cell proliferation. Exogenous AML1 may therefore be useful for expansion of hematopoietic stem-progenitor cells.

Description: In this study, we synthesized a random poly[(N-isopropylacrylamide)-co-(2-hydroxyethylmethacrylate)-co-(N-methylolacrylamide)] [poly(NIPAAm-co-HEMA-co-NMA)] copolymer through free-radical polymerization. The NIPAAm, HEMA and NMA moieties were framed to provide thermoresponsiveness, water absorption and retention control, and chemical cross-linking to achieve stability in aqueous medium, respectively. The copolymer showed a significant change in optical transmittance with a variation in temperature due to the change in volume (i.e., hydrophilic/hydrophobic) between 25 °C and 40 °C, attributed to the lower critical solution temperature property of the NIPAAm moiety. The copolymers were wire-bar-coated onto polyethylene terephthalate (PET) fabric. Variation in the water contact angle affirmed the switchable wettability due to the change in temperature. We tested the coated fabrics for moisture absorption and release at different temperatures. The results at 20 °C and 37 °C indicated that the P2 copolymer had the highest moisture absorption and release capability. Therefore, the copolymers with tailored properties can be used as smart textiles for activity specific clothing.