Multiplex analysis of anti-apoptotic BCL2 family and caspase 3 activation by microbead arrays

Early apoptosis of monocytes induced by Helicobacter pylori infection through multiple pathways

Only a small percentage of people infected with Helicobacter pylori (H. pylori) will develop overt chronic gastric diseases. To understand the pathological mechanism, the action of H. pylori on monocyte apoptosis was detected. H. pylori co-culturing with peripheral blood monocytes, THP-1 or U937 cells result in early apoptosis at 6, 12, and 24 h after infection. The phosphorylated Bad and JNK were increased, and Bcl-2 was declined at 6, 12, and 24 h in peripheral blood monocytes after H. pylori infection. The phosphorylated Akt was augmented at 6 and 12 h post-infection. A slow apoptotic response was induced by H. pylori via Bad and Bcl-2 regulators, activated caspase-8 and caspase-9, and JNK at 24 h in THP-1 cells. Meanwhile, only Bad and JNK were involved in regulating U937 cells apoptosis at 24 h after infection. These results supported a novel mechanism of H. pylori escaping from monocytes by upregulation of early apoptosis and inhibition of late apoptosis. The differences among the three cells may reveal why H. pylori-derived disease occurs in relatively few people and provide a pathological mechanism whereby a treatment for H. pylori-derived disease may be developed.

Potential mechanisms of resistance to venetoclax and strategies to circumvent it

Background

Venetoclax (ABT-199), a first-in-class orally bioavailable BCL-2-selective inhibitor, was recently approved by the FDA for use in patients with 17p-deleted chronic lymphocytic leukemia who have received prior therapy. It is also being evaluated in numerous clinical trials for treating patients with various hematologic malignancies. As with any targeted cancer therapy, it is critically important to identify potential mechanisms of resistance, both for patient stratification and developing strategies to overcome resistance, either before it develops or as it emerges.

Methods

In order to gain a more comprehensive insight into the nature of venetoclax resistance mechanisms, we evaluated the changes in the BCL-2 family members at the genetic and expression levels in seven different venetoclax-resistant derived leukemia and lymphoma cell lines.

Results

Gene and protein expression analyses identified a number of different alterations in the expression of pro- and anti-apoptotic BCL-2 family members. In the resistant derived cells, an increase in either or both the anti-apoptotic proteins BCL-X_L or MCL-1, which are not targeted by venetoclax was observed, and either concomitant or exclusive with a decrease in one or more pro-apoptotic proteins. In addition, mutational analysis also revealed a mutation in the BH3 binding groove (F104L) that could potentially interfere with venetoclax-binding. Not all changes may be causally related to venetoclax resistance and may only be an epiphenomenon. For resistant cell lines showing elevations in BCL-X_L or MCL-1, strong synergistic cell killing was observed when venetoclax was combined with either BCL-X_L- or MCL-1-selective inhibitors, respectively. This highlights the importance of BCL-X_L- and MCL-1 as causally contributing to venetoclax resistance.

Conclusions

Overall our study identified numerous changes in multiple resistant lines; the changes were neither mutually exclusive nor universal across the cell lines tested, thus exemplifying the complexity and heterogeneity of potential resistance mechanisms. Identifying and evaluating their contribution has important implications for both patient selection and the rational development of strategies to overcome resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3383-5) contains supplementary material, which is available to authorized users.

Loss in MCL-1 function sensitizes non-Hodgkin's lymphoma cell lines to the BCL-2-selective inhibitor venetoclax (ABT-199)

As a population, non-Hodgkin's lymphoma (NHL) cell lines positive for the t(14;18) translocation and/or possessing elevated BCL2 copy number (CN; BCL2(High)) are exquisitely sensitive to navitoclax or the B-cell lymphoma protein-2 (BCL-2)-selective inhibitor venetoclax. Despite this, some BCL2(High) cell lines remain resistant to either agent. Here we show that the MCL-1-specific inhibitor A-1210477 sensitizes these cell lines to navitoclax. Chemical segregation of this synergy with the BCL-2-selective inhibitor venetoclax or BCL-XL-selective inhibitor A-1155463 indicated that MCL-1 and BCL-2 are the two key anti-apoptotic targets for sensitization. Similarly, the CDK inhibitor flavopiridol downregulated MCL-1 expression and synergized with venetoclax in BCL2(High) NHL cell lines to a similar extent as A-1210477. A-1210477 also synergized with navitoclax in the majority of BCL2(Low) NHL cell lines. However, chemical segregation with venetoclax or A-1155463 revealed that synergy was driven by BCL-XL inhibition in this population. Collectively these data emphasize that BCL2 status is predictive of venetoclax potency in NHL not only as a single agent, but also in the adjuvant setting with anti-tumorigenic agents that inhibit MCL-1 function. These studies also potentially identify a patient population (BCL2(Low)) that could benefit from BCL-XL (navitoclax)-driven combination therapy.

Genomic analysis and selective small molecule inhibition identifies BCL-X(L) as a critical survival factor in a subset of colorectal cancer

Background

Defects in programmed cell death, or apoptosis, are a hallmark of cancer. The anti-apoptotic B-cell lymphoma 2 (BCL-2) family proteins, including BCL-2, BCL-X_L, and MCL-1 have been characterized as key survival factors in multiple cancer types. Because cancer types with BCL2 and MCL1 amplification are more prone to inhibition of their respectively encoded proteins, we hypothesized that cancers with a significant frequency of BCL2L1 amplification would have greater dependency on BCL-X_L for survival.

Methods

To identify tumor subtypes that have significant frequency of BCL2L1 amplification, we performed data mining using The Cancer Genome Atlas (TCGA) database. We then assessed the dependency on BCL-X_L in a panel of cell lines using a selective and potent BCL-X_L inhibitor, A-1155463, and BCL2L1 siRNA. Mechanistic studies on the role of BCL-X_L were further undertaken via a variety of genetic manipulations.

Results

We identified colorectal cancer as having the highest frequency of BCL2L1 amplification across all tumor types examined. Colorectal cancer cell lines with BCL2L1 copy number >3 were more sensitive to A-1155463. Consistently, cell lines with high expression of BCL-X_L and NOXA, a pro-apoptotic protein that antagonizes MCL-1 activity were sensitive to A-1155463. Silencing the expression of BCL-X_L via siRNA killed the cell lines that were sensitive to A-1155463 while having little effect on lines that were resistant. Furthermore, silencing the expression of MCL-1 in resistant cell lines conferred sensitivity to A-1155463, whereas silencing NOXA abrogated sensitivity.

Conclusions

This work demonstrates the utility of characterizing frequent genomic alterations to identify cancer survival genes. In addition, these studies demonstrate the utility of the highly potent and selective compound A-1155463 for investigating the role of BCL-X_L in mediating the survival of specific tumor types, and indicate that BCL-X_L inhibition could be an effective treatment for colorectal tumors with high BCL-X_L and NOXA expression.