Caspase-8 activation by TRAIL monotherapy predicts responses to IAPi and TRAIL combination treatment in breast cancer cell lines

Abstract

The discovery of cancer cell-selective tumour necrosis factor-related apoptosis inducing ligand (TRAIL)-induced apoptosis generated broad excitement and development of TRAIL receptor agonists (TRA) as potential cancer therapy. Studies demonstrating the synergistic combination effect of SMAC mimetics and TRA further suggested potentially effective treatment in multiple tumour settings. However, predictive biomarkers allowing identification of patients that could respond to treatment are lacking. Here, we described a high throughput combination screen conducted across a panel of 31 breast cancer cell lines in which we observed highly synergistic activity between TRAIL and the inhibitors of apoptosis proteins (IAP) inhibitor (IAPi) AZD5582 in ~30% of cell lines. We detected no difference in the expression levels of the IAPi or TRAIL-targeted proteins or common modulators of the apoptotic pathway between the sensitive and resistant cell lines. Synergistic combination effect of AZD5582 and TRAIL correlated with sensitivity to TRAIL, but not to AZD5582 as a single agent. TRAIL treatment led to significantly greater activity of Caspase-8 in sensitive than in resistant cell lines (P=0.002). The majority (12/14) of AZD5582+TRAIL-resistant cell lines retained a functional cell death pathway, as they were sensitive to AZD5582+TNFα combination treatment. This suggested that failure of the TRAIL receptor complex to transduce the death signal to Caspase-8 underlies AZD5582+TRAIL resistance. We developed a 3D spheroid assay and demonstrated its suitability for the ex vivo analysis of the Caspase-8 activity as a predictive biomarker. Altogether, our study demonstrated a link between the functionality of the TRAIL receptor pathway and the synergistic activity of the IAPi+TRA combination treatment. It also provided a rationale for development of the Caspase-8 activity assay as a functional predictive biomarker that could allow better prediction of the response to IAPi+TRA-based therapies than the analysis of expression levels of protein biomarkers.

Death receptor 5 is activated by fucosylation in colon cancer cells

“…A). In a screen across a panel of breast cancer cell lines, TRAIL‐sensitive cells showed more caspase‐8 activity than TRAIL resistant cells . This has also been found in a subset of colorectal cancer cell lines .…”

Loss of MCL1 function sensitizes the MDA‐MB‐231 breast cancer cells to rh‐TRAIL by increasing DR4 levels

“…Indeed, a number of data suggest that therapeutic activation of TRAIL receptors may provide the specificity to tumor cells with broad tolerability (Polanski, Vincent, Polanska, Petreus, & Tang, 2015).…”

XIAP over-expression is an independent poor prognostic marker in Middle Eastern breast cancer and can be targeted to induce efficient apoptosis

“…Monotherapy using small molecular inhibitors or antibodies used for treatment of cancer have had their share of success and failure where some inhibitors/antibodies have done well when used alone [ 53 ], however, many experimental inhibitors/antibodies have failed due to either acquired resistance to therapy or increased toxicities following initial success [ 54 , 55 ]. On the other hand, these experimental agents have fared much better when used in combination with other inhibitors or chemotherapeutic agents [ 56 , 57 ]. An important advantage of using combination therapy is that usually sub-optimal doses are required to induce a synergistic response thereby decreasing the chances of toxicities that are usually present with using high doses with the same inhibitors alone.…”