Biomedical subjects

Marcus Järås

Publications and source records attributed to Marcus Järås.

3 recordsLinked to original sources

PubMed2006

Human short-term repopulating cells have enhanced telomerase reverse transcriptase expression.

Telomerase activity has been suggested to be critically involved in hematopoietic stem cell (HSC) self-renewal. However, it has been unclear whether human HSCs have telomerase activity and how telomerase activity is regulated within the HSC and progenitor pool. Here, we isolated living cord-blood (CB) CD34(+) cells with up-regulated human telomerase reverse transcriptase (hTERT) expression by using an hTERT-reporting adenoviral vector encoding destabilized green fluorescent protein (dGFP) driven by the hTERT promoter, and functionally characterized them in comparison with control vector-transduced CD34(+) cells expressing GFP. Following a 2-day serum-free transduction protocol, cells were sorted into a dGFP(+) and a GFP(+) fraction. Cell-cycle analysis revealed that the dGFP(+) cells had a greater proportion of cells in S/G(2)/M phase compared with the GFP(+) cells, (56% +/- 1.8% vs 35% +/- 4.3%; P < .001) and fewer cells in G(0) phase (8.1% +/- 3.0% vs 20% +/- 4.7%; P < .01) However, the colony-forming and short-term nonobese diabetic/severe combined immunodeficient (NOD/SCID) B2m(-/-) mice bone marrow-repopulating capacities were similar between the dGFP(+) and the GFP(+) cells. Interestingly, the dGFP(+) cells had a 6-fold lower repopulating capacity in NOD/SCID mice compared with the GFP(+) cells and lacked secondary NOD/SCID B2m(-/-) mice bone marrow-repopulating capacity. Thus, up-regulation of hTERT expression within the CB HSC pool is accompanied by decreased self-renewal capacity.

Animals↗

PubMed2006

Detection of cell cycle- and differentiation stage-dependent human telomerase reverse transcriptase expression in single living cancer cells.

Elevated telomerase activity is an important molecular signature of cancer cells and primitive cells in regenerative tissues. However, isolation of single living cells with endogenous telomerase activity has not yet been possible. Here, we developed adenovirus serotype 35 tropism-based vectors encoding destabilized enhanced green fluorescence protein with a half-life of 2 h (d2EGFP) driven by the human telomerase reverse transcriptase (hTERT) promoter. As assessed in telomerase-positive or -negative cell lines, the d2EGFP expression positively correlated with hTERT transcript content and telomerase activity. In retinoic acid-induced differentiating HL-60 cells, the d2EGFP expression is diminished in the same manner as the hTERT expression. Individual cells from HeLa and HL-60 cell lines exhibited heterogeneous d2EGFP expression, which was cell cycle dependent, as the sorted d2EGFP+ HL-60 cells contained twice as many cells in S/G2/M phase of the cell cycle compared with the d2EGFP- HL-60 cells. However, both cell populations exhibited the same proliferation and regeneration capacities. Heterogeneous d2EGFP expression was also detected in xenograft glioblastoma multiforme cells with tumor formation capacity. Thus, d2EGFP expression reported cell cycle- and differentiation stage-dependent hTERT expression. Our study facilitates isolation and characterization of single living cells with telomerase activity.

Adenoviridae↗

PubMed2006

Increased expression of cyclin A1 protein is associated with all-trans retinoic acid-induced apoptosis.

Deregulated cell growth and inhibition of apoptosis are hallmarks of cancer. All-trans retinoic acid induces clinical remission in patients with acute promyelocytic leukemia by inhibiting cell growth and inducing differentiation and apoptosis of the leukemic blasts. An important role of the cell cycle regulatory protein, cyclin A1, in the development of acute myeloid leukemia has previously been demonstrated in a transgenic mouse model. We have recently shown that there was a direct interaction between cyclin A1 and a major all-trans retinoic acid receptor, RAR alpha, following all-trans retinoic acid treatment of leukemic cells. In the present study, we investigated whether cyclin A1 might be involved in all-trans retinoic acid-induced apoptosis in U-937 leukemic cells. We found that all-trans retinoic acid-induced apoptosis was associated with concomitant increase in cyclin A1 expression. However, there was no induction of cyclin A1 mRNA expression following the all-trans retinoic acid-induced apoptosis. Treatment of cells with a caspase inhibitor was not able to prevent all-trans retinoic acid-induced up-regulation of cyclin A1 expression. Interestingly, induced cyclin A1 expression in U-937 cells led to a significant increase in the proportion of apoptotic cells. Further, U-937 cells overexpressing cyclin A1 appeared to be more sensitive to all-trans retinoic acid-induced apoptosis indicating the ability of cyclin A1 to mediate all-trans retinoic acid-induced apoptosis. Induced cyclin E expression was not able to initiate cell death in U-937 cells. Our results indicate that cyclin A1 might have a role in apoptosis by mediating all-trans retinoic acid-induced apoptosis.

Apoptosis↗