Dynamic BH3 profiling identifies active BH3 mimetic combinations in non-small cell lung cancer

Abstract

Conventional chemotherapy is still of great utility in oncology and rationally constructing combinations with it remains a top priority. Drug-induced mitochondrial apoptotic priming, measured by dynamic BH3 profiling (DBP), has been shown in multiple cancers to identify drugs that promote apoptosis in vivo. We therefore hypothesized that we could use DBP to identify drugs that would render cancers more sensitive to conventional chemotherapy. We found that targeted agents that increased priming of non-small cell lung cancer (NSCLC) tumor cells resulted in increased sensitivity to chemotherapy in vitro. To assess whether targeted agents that increase priming might enhance the efficacy of cytotoxic agents in vivo as well, we carried out an efficacy study in a PC9 xenograft mouse model. The BH3 mimetic navitoclax, which antagonizes BCL-xL, BCL-w, and BCL-2, consistently primed NSCLC tumors in vitro and in vivo. The BH3 mimetic venetoclax, which electively antagonizes BCL-2, did not. Combining navitoclax with etoposide significantly reduced tumor burden compared to either single agent, while adding venetoclax to etoposide had no effect on tumor burden. Next, we assessed priming of primary patient NSCLC tumor cells on drugs from a clinically relevant oncology combination screen (CROCS). Results confirmed for the first time the utility of BCL-xL inhibition by navitoclax in priming primary NSCLC tumor cells and identified combinations that primed further. This is a demonstration of the principle that DBP can be used as a functional precision medicine tool to rationally construct combination drug regimens that include BH3 mimetics in solid tumors like NSCLC.

Targeting the BCL-2-regulated apoptotic pathway for the treatment of solid cancers

“…In squamous cell lung carcinoma, dual inhibition of MCL-1 and BCL-XL induced synergistic tumour cell death, and when combined with fibroblast growth factor receptor (FGFR)-targeted therapy, produced durable treatment responses in FGFR1- overexpressing lung squamous cell carcinoma [ 79 ]. Similar results were also observed in malignant pleural mesothelioma, NSCLC and colorectal cancer [ 8 , 12 , 19 , 40 , 80 , 81 ]. In these cancers, BCL-XL is the dominant survival factor as its sole targeting had a greater effect compared with the targeting of MCL-1 alone.…”

“…However, given the key and often compensatory roles these proteins play in non-malignant cells, co-inhibition of two or more pro-survival proteins potentiates the opportunity for associated toxicities. The simultaneous disarmament of BCL-XL and MCL-1 with BH3-mimetics in mice is lethal due to acute liver toxicity [ 12 , 79 ] as both these proteins are critical for hepatocyte survival [ 88 ]. These pro-survival proteins are also essential for megakaryocyte survival [ 89 ].…”

Microfluidic-based dynamic BH3 profiling predicts anticancer treatment efficacy

“…To solve this problem, a new microscopy-based version created by the Letai lab, called highthroughput DBP (HT-DBP), has been developed using 384 well plates, automatic multi-well dispensers, and automated highthroughput fluorescence microscopes. This method uses approximately 5k cells per treatment and has been successfully utilized to screen hundreds of anticancer drugs in colon cancer 23 and nonsmall cell lung cancer 59 patients. However, HT-DBP requires a predetermination of the optimal BIM peptide concentration (demanding more time than μDBP and around 250k more cells), expensive equipment, and highly trained personnel to be performed; thus, it has to be centralized in a specialized laboratory, hampering its broad application in the clinic.…”

MCL-1 is a clinically targetable vulnerability in breast cancer

“…Indeed, the ability of cancer therapeutics to prime individual cancers for apoptosis can be gauged ex vivo using an adapted BH3-profiling protocol [ 138 ]. The utility of inhibiting different pro-survival BCL-2 proteins in combination with chemotherapy has been demonstrated using freshly isolated non-small cell lung cancer patient samples [ 139 ]. It can be envisioned that such technologies could pave the way for personalized use of BH3 mimetics in breast cancer.…”