Combined effects of aberrant MEK1 activity and BCL2 overexpression on relieving the cytokine dependency of human and murine hematopoietic cells

The MEK1 oncoprotein plays a critical role in Ras/Raf/ MEK/MAPK-mediated transmission of mitogenic signals from cell surface receptors to the nucleus. In order to examine this pathway's role in leukemic transformation, a conditionally active (β-estradiol-inducible) form of the MEK1 protein was created by ligating a cDNA encoding an N-terminal truncated form of MEK1 to the hormone-binding domain of the estrogen receptor (ER). We introduced this chimeric ΔMEK1:ER oncoprotein into cytokine-dependent human TF-1 and murine FDC-P1 hematopoietic cell lines. Two different types of cells were recovered after drug selection in medium containing either cytokine or β-estradiol: (1) cells that expressed the ΔMEK1:ER oncoprotein but remained cytokine-dependent and (2) MEK1-responsive cells that grew in response to ΔMEK1:ER activation. Cytokine-dependent cells were recovered 102 to 104 times more frequently than MEK1-responsive cells depending upon the particular cell line. To determine whether BCL2 overexpression could synergize with the ΔMEK1:ER oncoprotein in relieving cytokine dependence, the cytokine-dependent ΔMEK1:ER-expressing cells were infected with a BCL2-containing retrovirus, and the frequency of MEK1-responsive cells determined. BCL2 overexpression, by itself, did not relieve cytokine dependency of the parental cells, however, it did increase the frequency at which MEK1-responsive cells were recovered approximately 10-fold. ΔMEK1:ER+BCL2 cells remained viable for at least 3 days after estradiol deprivation, whereas viability was readily lost upon withdrawal of β-estradiol in the MEK1-responsive cells which lacked BCL2 overexpression. The MAP kinases, ERK1 and ERK2 were activated in response to ΔMEK1:ER stimulation in both ΔMEK1:ER and ΔMEK1:ER+BCL2 cells. As compared to the cytokine-dependent ΔMEK1:ER and BCL2 infected cells, MEK1-responsive BCL2 infected cells expressed higher levels of BCL2. While both MEK1-responsive ΔMEK1:ER and ΔMEK1:ER+BCL2 infected cells expressed cDNAs encoding the autocrine cytokine GM-CSF, more GM-CSF cDNAs and bioactivity were detected in the MEK1-responsive ΔMEK1:ER+BCL2 cells than in the MEK1-responsive cells lacking BCL2 or cytokine-dependent cells. These conditionally transformed cells will be useful in furthering our understanding of the roles MEK1 and BCL2 play in the prevention of apoptosis in hematopoietic cells

Combined effects of aberrant MEK1 activity and BCL2 overexpression on relieving the cytokine dependency of human and murine hematopoietic cells

The MEK1 oncoprotein plays a critical role in Ras/Raf/ MEK/MAPK-mediated transmission of mitogenic signals from cell surface receptors to the nucleus. In order to examine this pathway's role in leukemic transformation, a conditionally active (ß-estradiol-inducible) form of the MEK1 protein was created by ligating a cDNA encoding an N-terminal truncated form of MEK1 to the hormone-binding domain of the estrogen receptor (ER). We introduced this chimeric ?MEK1:ER oncoprotein into cytokine-dependent human TF-1 and murine FDC-P1 hematopoietic cell lines. Two different types of cells were recovered after drug selection in medium containing either cytokine or ß-estradiol: (1) cells that expressed the ?MEK1:ER oncoprotein but remained cytokine-dependent and (2) MEK1-responsive cells that grew in response to ?MEK1:ER activation. Cytokine-dependent cells were recovered 102 to 104 times more frequently than MEK1-responsive cells depending upon the particular cell line. To determine whether BCL2 overexpression could synergize with the ?MEK1:ER oncoprotein in relieving cytokine dependence, the cytokine-dependent ?MEK1:ER-expressing cells were infected with a BCL2-containing retrovirus, and the frequency of MEK1-responsive cells determined. BCL2 overexpression, by itself, did not relieve cytokine dependency of the parental cells, however, it did increase the frequency at which MEK1-responsive cells were recovered approximately 10-fold. ?MEK1:ER+BCL2 cells remained viable for at least 3 days after estradiol deprivation, whereas viability was readily lost upon withdrawal of ß-estradiol in the MEK1-responsive cells which lacked BCL2 overexpression. The MAP kinases, ERK1 and ERK2 were activated in response to ?MEK1:ER stimulation in both ?MEK1:ER and ?MEK1:ER+BCL2 cells. As compared to the cytokine-dependent ?MEK1:ER and BCL2 infected cells, MEK1-responsive BCL2 infected cells expressed higher levels of BCL2. While both MEK1-responsive ?MEK1:ER and ?MEK1:ER+BCL2 infected cells expressed cDNAs encoding the autocrine cytokine GM-CSF, more GM-CSF cDNAs and bioactivity were detected in the MEK1-responsive ?MEK1:ER+BCL2 cells than in the MEK1-responsive cells lacking BCL2 or cytokine-dependent cells. These conditionally transformed cells will be useful in furthering our understanding of the roles MEK1 and BCL2 play in the prevention of apoptosis in hematopoietic cells

Microbial differences between dental plaque and historic dental calculus are related to oral biofilm maturation stage

Background: Dental calculus, calcified oral plaque biofilm, contains microbial and host biomolecules that can be used to study historic microbiome communities and host responses. Dental calculus does not typically accumulate as much today as historically, and clinical oral microbiome research studies focus primarily on living dental plaque biofilm. However, plaque and calculus reflect different conditions of the oral biofilm, and the differences in microbial characteristics between the sample types have not yet been systematically explored. Here, we compare the microbial profiles of modern dental plaque, modern dental calculus, and historic dental calculus to establish expected differences between these substrates. Results: Metagenomic data was generated from modern and historic calculus samples, and dental plaque metagenomic data was downloaded from the Human Microbiome Project. Microbial composition and functional profile were assessed. Metaproteomic data was obtained from a subset of historic calculus samples. Comparisons between microbial, protein, and metabolomic profiles revealed distinct taxonomic and metabolic functional profiles between plaque, modern calculus, and historic calculus, but not between calculus collected from healthy teeth and periodontal disease-affected teeth. Species co-exclusion was related to biofilm environment. Proteomic profiling revealed that healthy tooth samples contain low levels of bacterial virulence proteins and a robust innate immune response. Correlations between proteomic and metabolomic profiles suggest co-preservation of bacterial lipid membranes and membrane-associated proteins. Conclusions: Overall, we find that there are systematic microbial differences between plaque and calculus related to biofilm physiology, and recognizing these differences is important for accurate data interpretation in studies comparing dental plaque and calculus.</p