Bcl-2 | EPFL Graph Search

Bcl-2 est le prototype d'une famille de gènes qui peuvent être soit pro-apoptotiques – entre autres Bax, Bak, Bok, Bad, Bid et Bim – ou anti-apoptotiques – parmi lesquels Bcl-2, Bcl-xL, Bcl-w, Nr13 (ou Nrh - DIVA/BOO). À l'heure actuelle, il y a en tout 30 membres identifiés chez les eucaryotes supérieurs. La protéine Bcl-2 est une protéine de 239 acides aminés dont le gène est situé sur le chromosome 18 humain au locus q21.33. Elle est constituée de quatre domaines d’homologie qui sont aussi présents chez d’autres protéines de la même famille. Ce sont ces domaines, ainsi que son domaine trans-membranaire qui lui permettent d’avoir une action sur l’apoptose. Origine du nom et lien avec le cancer Bcl-2 doit son nom à l'anglais B-cell lymphoma 2 (lymphome à cellules B). Ce nom vient du fait que Bcl-2 fut la deuxième protéine à être découverte en lien avec le lymphome folliculaire humain à cellules B. Ce cancer est dû en grande partie à une translocation des chromosomes 14

NRF2 Activation Confers Resistance to eIF4A Inhibitors in Cancer Therapy

Linlin Cao

Inhibition of the eIF4A RNA helicase with silvestrol and related compounds is emerging as a powerful anti-cancer strategy. We find that a synthetic silvestrol analogue (CR-1-31 B) has nanomolar activity across many cancer cell lines. It is especially active against aggressive MYC+/BCL2+ B cell lymphomas and this likely reflects the eIF4A-dependent translation of both MYC and BCL2. We performed a genome-wide CRISPR/Cas9 screen and identified mechanisms of resistance to this new class of therapeutics. We identify three negative NRF2 regulators (KEAP1, CUL3, CAND1) whose inactivation is sufficient to cause CR1-31-B resistance. NRF2 is known to alter the oxidation state of translation factors and cause a broad increase in protein production. We find that NRF2 activation particularly increases the translation of some eIF4A-dependent mRNAs and restores MYC and BCL2 production. We know that NRF2 functions depend on removal of sugar adducts by the frutosamine-3-kinase (FN3K). Accordingly, loss of FN3K results in NRF2 hyper-glycation and inactivation and resensitizes cancer cells to eIF4A inhibition. Together, our findings implicate NRF2 in the translation of eIF4A-dependent mRNAs and point to FN3K inhibition as a new strategy to block NRF2 functions in cancer.

2021

Functional analysis and knock‐down phenotype of BCL9 and BCL9L in cancer cell lines

Fanny Bringolf

Therapy‐resistant tumor cells often display EMT and stem cell‐like traits. The canonical Wnt pathway has been associated with these phenotypes in many cancer types. Our group has shown in mice that two proteins of this pathway, Bcl9 and Bcl9l, participate in controlling Wnt-mediated stem cell traits. We hypothesized that inhibition of BCL9/BCL9L could be a potential strategy to revert cells with stem‐cell properties to a differentiated epithelial phenotype, and thus also re‐establish their sensitivity to chemotherapy. Preliminary experiments in a human colon cancer cell line showed that BCL9L single knock‐down (KD) surprisingly already completely abrogated expression of selected Wnt target genes, despite the presence of the second paralog BCL9, which was even up‐regulated upon loss of BCL9L. This observation raised the question whether the remaining BCL9 protein might be dysfunctional, or whether BCL9 and BCL9L are, against our expectation, not functionally redundant. Thus, we characterized Bcl9 expression at transcriptional and genomic level by reverse transcription and DNA sequencing. By sequencing, we identified three different BCL9 mRNA species in SW480 cells (wild‐type (WT) and two isoforms carrying short deletions), which we also confirmed to be present in other carcinoma cell lines. No abnormalities were found on the genomic level. We then assessed Bcl9 and Bcl9l expression at protein level using standard Western blotting. In the different cell lines the proteins showed distinct molecular weights, which may correspond to different posttranslational modifications that could be associated with different functions. To generally explore BCL9 function, we silenced the gene using lentivirus vector‐based expression of shRNAs. Further analysis of the observed Bcl9 KD on a broad panel of Wnt target genes and comparison with the Bcl9l KD phenotype will help elucidating Bcl9 and Bcl9L function

2010

The Bcl9-beta-catenin interface as a potential therapeutic target for colorectal cancer

Andreas Eduard Moor

Aberrantly active Wnt signaling is the hallmark driver of colorectal cancer (CRC). Bcl9/9l proteins are components of the main transcriptional activation complex of canonical Wnt signaling and interact with beta-catenin via a highly conserved homology domain (HD2). Intestinal loss of Bcl9 affects wound healing and Lgr5+-cancer stem cell (CSC) maintenance, but does not perturb normal tissue homeostasis. The aim of the present thesis was to validate the Bcl9-Î²-catenin interaction as a potential target for modulating Wnt signaling and abolishing intestinal stemness traits in colorectal cancer. We investigated the role of the Bcl9-beta-catenin interaction in the mouse AOM-DSS chemical carcinogenesis CRC model. Subsequently, we validated our observations in an independent transgenic APC-Kras CRC model (truncated APC tumor suppressor and mutated Kras expressed in the intestine). The expression of Bcl9 proteins was abolished exclusively in the gastrointestinal epithelium using constitutive or inducible Cre-recombinase expressed under the control of the Villin promoter. To corroborate that the loss of Bcl9 phenotype was due to the abrogation of the Bcl9-beta-catenin interaction and not to a Î²-catenin-independent function of Bcl9, we made use of an additional Bcl9 mutant mouse strain in which only the HD2 of both Bcl9 proteins was deleted, selectively preventing the Bcl9-beta-catenin interaction. The inducible deletion of Bcl9 in established AOM-DSS tumors led to a loss in stem cell, Wnt and EMT gene expression signatures, recapitulating the phenotype that we previously described when Bcl9 was deleted constitutively. A 14d partial decrease of Bcl9 proved sufficient to suppress the expression of mesenchymal marker Vimentin in a cell autonomous fashion. Importantly, AOM-DSS tumors with Bcl9 proteins selectively lacking the HD2 beta-catenin interaction domain displayed the same phenotype as observed in tumors that entirely lacked Bcl9 proteins. Bcl9-knockout tumors induced in the Wnt active APC-Kras tumor model were compared with their wild-type counterparts. Wild-type APC-Kras mutant tumors displayed fewer mesenchymal traits when compared to AOM-DSS induced tumors. Global gene expression analysis by RNA sequencing confirmed a strong positive correlation between Bcl9/9l-dependent transcriptional changes in both independent tumor models. Genes differentially expressed between wild-type and Bcl9/9l ablated tumors were used to probe CRC databases for correlation with patient outcome and revealed a strong association with vastly improved disease-free and overall survival, independent of clinical and molecular parameters. We have shown that preventing the interaction of Bcl9 with beta-catenin in established tumors in Wnt-activated CRC models rapidly resulted in the loss of stemness and mesenchymal traits and concomitant induction of a more differentiated phenotype. Importantly, these loss-of-Bcl9 traits are prognostic for favorable outcome in CRC patients and we have not observed any overt anomalies upon intestinal ablation of Bcl9 in adult mice. Overall, our observations indicate that targeting the Bcl9-beta-catenin interaction in Wnt-activated tumors might be well tolerated and a generally applicable pharmacological strategy to target CSCs to potentially prevent tumor recurrence and improve progression free survival.

EPFL2014