Dynamic BH3 profiling offers personalized lung cancer therapies

Eighty-five percent of diagnosed cases of lung cancer are non-small cell lung cancer (NSCLC). In this group, 5% of patients show molecular alterations in the ALK gene involved in cell multiplication. The use of inhibitors against this oncogene — one of the most effective strategies against this type of cancer — has benefited many patients. But, is it possible to know if the treatment will be effective in all those affected?

Now, a study led by the University of Barcelona reveals that the functional assay dynamic BH3 profiling (DBP) can predict whether this treatment will be effective in these cancer patients and thus improve personalized therapies. This technique achieves with tumors something very similar to what an antibiogram achieves with a bacterial infection: determining which therapy will be most effective by testing it directly on living cells.

The technique, which helps to select the best drug for each patient, was patented in 2015 by the Dana-Farber Cancer Institute (Boston, United States) and its co-inventor is Joan Montero, professor at the UB's Faculty of Medicine and Health Sciences and at the Bioengineering, Biomaterials and Nanomedicine Networking Biomedical Research Centre (CIBER-BBN).

The new study, published in Nature's journal Cell Death and Disease, is led by Professor Joan Montero and its first author is researcher Fernando Martín, a member of the UB, the Institute for Bioengineering of Catalonia (IBEC) and CIBERBBN. Teams from the UB's Faculty of Physics, Hospital Clínic, August Pi i Sunyer Biomedical Research Institute (IDIBAPS) and the Catalan Institute of Oncology (ICO) are also collaborating in the paper.

The study, conducted using animal models and patient biopsies, also reveals for the first time that the MCL-1 protein plays a key role in tumor resistance to this type of therapy. It also shows that molecules known as BH3 mimetics can improve the effect of cancer treatments by preventing tumor adaptations to inhibitors of anaplastic lymphoma protein kinase (ALK), one of the main treatments for this cancer.

Predicting the response of the most common lung cancer drugs

Each tumor is unique, and predicting the therapeutic response to non-small cell lung cancer is a breakthrough in personalized medicine. Given this challenge in biomedicine, the study confirms that the dynamic BH3 profiling technique has an excellent predictive capacity for tumor cell response to ALK inhibitors.

ALK inhibitors are used early in disease in patients with non-small cell lung cancer who show molecular alterations in this oncogene. Currently, four generations of ALK inhibitors have been developed with clinical efficacy superior to chemotherapy.

These targeted therapies confer the longest survival in non-small cell lung cancer and are better tolerated than cytotoxic agents. The use of ALK inhibitors in the clinic not only increases patient survival, but also improves their quality of life."

Joan Montero, UB's Department of Biomedicine

"In this context, dynamic BH3 profiling could complement the application of genomic assays and mass sequencing that routinely guide the use of these targeted therapies in cancer patients, especially in complex cases", explains the professor.

How do ALK inhibitors work in cancer?

In NSCLC-type cancer patients, a fusion of two genes — ALK and the EML4 gene in 90% of cases — results in a new gene capable of encoding a mutated protein and activating signalling pathways that promote tumor proliferation. "In their therapeutic action, ALK inhibitors specifically bind to the active site of the chimera protein and prevent its kinase activity. In this way, these drugs inhibit the phosphorylation and activation of other target proteins involved in tumor cell growth and survival", says Fernando Martín.

Unlike many chemotherapeutic agents, "ALK inhibitors can cross the blood-brain barrier and reach the central nervous system. As one third of patients with advanced-stage NSCLC cancer metastasize to the brain, this ability is particularly beneficial in the fight against tumors. This type of therapy is also applicable in anaplastic large cell lymphoma or neuroblastoma", says the researcher.

Tumor cells escaping death by apoptosis

Despite advances in treatment, the therapeutic response to ALK inhibitors is not always durable. Cancer cells that persist are resistant to death by apoptosis (programmed cell death) and treatment options against cell resistance are limited.

The study describes for the first time that the anti-apoptotic protein MCL-1 also plays a key role in resistance to these therapies. "One of the key features of therapy-resistant cells is the ability to avoid apoptotic cell death, a cellular mechanism regulated by the BCL-2 family of proteins. The balance between pro- and anti-apoptotic components ultimately regulates resistance to cell death and adaptation to therapy", say the researchers.

In previous studies, the authors described how anti-apoptotic proteins of the BCL-2 family can protect lung cancer cells against targeted therapies against oncogenes such as KRAS or EGFR. However, the role of this family in resistance to ALK inhibitors was unknown.

In addition, dynamic BH3 profiling also allows us to decipher the anti-apoptotic adaptations that arise in response to ALK inhibitors. "These acute adaptations can be prevented by using BH3 mimetics (small molecules that inhibit anti-apoptotic proteins with high specificity) to enhance the effect of treatment in vitro and in vivo", say the experts.

"For example, the drug Venetoclax — an inhibitor of the anti-apoptotic protein BCL-2 — has been successfully approved for clinical use. In parallel, inhibitors of other anti-apoptotic proteins such as MCL-1 are being evaluated in clinical trials", they continue. "Our study also proposes alternatives to the use of BH3 mimetics to indirectly but effectively inhibit these proteins and substantially enhance the effect of ALK inhibitors".

Among the immediate future projects, the team will push for further research to determine whether these anti-apoptotic resistances can manifest over longer periods of drug exposure (e.g. therapy-induced senescence). "It would also be very important to decipher what proportion of patients could benefit from the use of the dynamic BH3 profiling technique, and from the combination with BH3 mimetics and other drugs against anti-apoptotic proteins", conclude Joan Montero and Fernando Martín.