Unknown,Transcriptomics,Genomics,Proteomics

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STK38 is a Key Regulator of MYC Transcriptional Activity in Human B lymphoma cells

ABSTRACT: Post-translational regulation of the MYC Transcription Factor (TF), including its phosphorylation and ubiquitination, plays an important role in determining cell proliferation and apoptosis and has been implicated in tumorigenesis. Using a computational systems biology approach, followed by biochemical and functional validation, we have characterized the role of the STK38 kinase, an NDR family serine-threonine kinase, as a key modulator of MYC transcriptional activity in human B cells, affecting MYC protein stability in a signal-dependent fashion. Specifically, we show that in human B lymphoma ST486 cells STK38 is a key mediator of BCR pathway signaling, affecting MYC protein turnover and its phosphorylation at Ser62 in kinase-activity-dependent manner. STK38 inactivation abrogates apoptosis following BCR activation while its silencing mediates MYC protein degradation via canonical proteolytic pathways. This suggests that STK38 could provide an effective therapeutic target in MYC-dependent malignancies. ST486 human Burkitt's lymphoma cells were transduced with STK38 shRNA lentiviral vectors.

ORGANISM(S): Homo sapiens

SUBMITTER: Mariano Alvarez

PROVIDER: E-GEOD-20229 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Similar to resting mature B cells, where the B-cell antigen receptor (BCR) is essential for cellular survival, surface BCR expression is conserved in most mature B cell lymphomas. The identification of activating BCR mutations and the growth disadvantage upon BCR knockdown of cells of certain lymphoma entities has led to the view that BCR signaling is required for tumour cell survival. Consequently, the BCR signaling machinery has become a new target in the therapy of B cell malignancies. Here, we studied the effects of BCR ablation on MYC-driven mouse B cell lymphomas and compared them to observations in human Burkitt lymphoma. Whereas BCR ablation did not, per se, significantly affect lymphoma growth, BCR-negative (BCR-) tumour cells rapidly disappeared in the presence of their BCR-expressing (BCR+) counterparts in vitro and in vivo. This required neither cellular contact, nor factors released by BCR+ tumour cells. Instead, BCR loss induced the rewiring of central carbon metabolism increasing the sensitivity of receptor-less lymphoma cells to nutrient restriction. The BCR attenuated GSK3β activity to support MYC-controlled gene expression. BCR- tumour cells exhibited increased GSK3β activity and were rescued from their competitive growth disadvantage by GSK3β. BCR-negative lymphoma variants that restored competitive fitness, normalized GSK3β following constitutive activation of the MAPK pathway, commonly through Ras mutations. Similarly, in Burkitt lymphoma, activating RAS mutations may propagate Ig-crippled tumour cells, which usually represent a minority of the tumour bulk. Thus, while BCR expression enhances lymphoma cell fitness, BCR-targeted therapies may profit from combinations with drugs targeting BCR-less tumour cells. In this dataset, we included the expression data obtained from BCR-positive (BCR+) and BCR-negative (BCR-) lymphoma cells co-cultured for 4 days in presence or absence of GSK3b inhibitor, CHIR99021. These data were used to obtain genes that are regulated by the BCR through GSK3b inhibition.

Project description:Similar to resting mature B cells, where the B-cell antigen receptor (BCR) is essential for cellular survival, surface BCR expression is conserved in most mature B cell lymphomas. The identification of activating BCR mutations and the growth disadvantage upon BCR knockdown of cells of certain lymphoma entities has led to the view that BCR signaling is required for tumour cell survival. Consequently, the BCR signaling machinery has become a new target in the therapy of B cell malignancies. Here, we studied the effects of BCR ablation on MYC-driven mouse B cell lymphomas and compared them to observations in human Burkitt lymphoma. Whereas BCR ablation did not, per se, significantly affect lymphoma growth, BCR-negative (BCR-) tumour cells rapidly disappeared in the presence of their BCR-expressing (BCR+) counterparts in vitro and in vivo. This required neither cellular contact, nor factors released by BCR+ tumour cells. Instead, BCR loss induced the rewiring of central carbon metabolism increasing the sensitivity of receptor-less lymphoma cells to nutrient restriction. The BCR attenuated GSK3β activity to support MYC-controlled gene expression. BCR- tumour cells exhibited increased GSK3β activity and were rescued from their competitive growth disadvantage by GSK3β. BCR-negative lymphoma variants that restored competitive fitness, normalized GSK3β following constitutive activation of the MAPK pathway, commonly through Ras mutations. Similarly, in Burkitt lymphoma, activating RAS mutations may propagate Ig-crippled tumour cells, which usually represent a minority of the tumour bulk. Thus, while BCR expression enhances lymphoma cell fitness, BCR-targeted therapies may profit from combinations with drugs targeting BCR-less tumour cells. In this dataset, we included the expression data obtained from BCR-positive (BCR+), BCR-negative (BCR-) and BCR-independent lymphoma cells co-cultured for four days in presence or absence of GSK3b inhibitor, CHIR99021. This data was used to a) identify genes regulated by the BCR through GSK3b inhibition, and b) identify genes that confers BCR-independency to lymphoma variants resistant to BCR loss.

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STK38 is a Key Regulator of MYC Transcriptional Activity in Human B lymphoma cells

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