Protein Inhibitor Approach Gets Reassessed for Cancer Therapy

Researchers have developed a novel technique that allows them to dial up or tone down the amount of a certain metastatic protein inhibitor (BACH1) within a cell. This could provide a new path in cancer research that reassesses the effectiveness of protein inhibitors to treat disease.

Led by a team of Stony Brook University scientists, the study involves adjusting the levels of BACH1 using a gene circuit placed into human breast metastatic cells. Their findings “Nonmonotone invasion landscape by noise-aware control of metastasis activator levels” are published in Nature Chemical Biology.

“A major pharmacological assumption is that lowering disease-promoting protein levels is generally beneficial. For example, inhibiting metastasis activator BACH1 is proposed to decrease cancer metastases. Testing such assumptions requires approaches to measure disease phenotypes while precisely adjusting disease-promoting protein levels,” the investigators wrote.

“Here we developed a two-step strategy to integrate protein-level tuning, noise-aware synthetic gene circuits into a well-defined human genomic safe harbor locus. Unexpectedly, engineered MDA-MB-231 metastatic human breast cancer cells become more, then less, and then more invasive as we tune BACH1 levels up, irrespective of the native BACH1. BACH1 expression shifts in invading cells, and expression of BACH1ʼs transcriptional targets confirm BACH1ʼs nonmonotone phenotypic and regulatory effects.

“Thus, chemical inhibition of BACH1 could have unwanted effects on invasion. Additionally, BACH1ʼs expression variability aids invasion at high BACH1 expression. Overall, precisely engineered, noise-aware protein-level control is necessary and important to unravel disease effects of genes to improve clinical drug efficacy.”

Use of protein inhibitors

Biomedicine relies upon the use of protein inhibitors based on the assumption that lowering disease-promoting protein levels or activity is generally beneficial when treating cancer. But, according to Gabor Balazsi, PhD, lead author of the study, when it comes to oncogenes, which produce cancer-promoting proteins, manipulating them by way of an “elimination only” approach within cancer cells—the most common method—is not necessarily the best way to develop treatments against cancer.

Balazsi and colleagues found that BACH1, which is highly expressed in many forms of metastatic cancer such as lung and breast, can be both an activator or inhibitor of cancer cell invasion in triple-negative breast cancer cells in culture.

“We developed a two-step technological pipeline that creates a kind of ‘landing pad’ in which BACH1 or other genes can be introduced safely into any human cell line, like a door that opens to the right key,” summarized Balázsi, the Henry Laufer professor in the Louis and Beatrice Laufer Center for Physical & Quantitative Biology, and professor of biomedical engineering at Stony Brook University.

Dimmer switch

The team used various ways, including CRISPR, to genetically manipulate the cells and create the landing pad to complete the first step. The second step involved developing synthetic gene circuits to control the amount of protein. These circuits enabled them to employ a “dimmer switch” that controls the amount or percentage of BACH1 placed into cancer cells.

“Think of this work like a light switch, however, one that works not just at ‘on’ and ‘off,’ but with a sophisticated dimmer capacity. While most research methods involving BACH1 or other cancer-promoting proteins turn the light switch on (activate) or off (inhibit), we have a fine-tuned dimmer where we can adjust the amount of the metastatic activator to intermediate percentages by way of the landing pad platform,” explained Balázsi.

What surprised the researchers in testing BACH1 in the cancer cell invasion model is that lowering the protein level did not always inhibit metastatic processes, and increasing it did not always increase cancer cell invasion.

They wrote: “Unexpectedly, engineered MDA-MB-231 human breast metastatic cells become more, then less, and then more invasive as we tune BACH1 levels up, irrespective of the native BACH1. BACH1 expression shifts in invading cells, and expression of BACH1 transcription targets, confirm BACH1’s nonmonotone phenotype and regulatory effects. Thus, chemical inhibition of BACH1 could have unwanted effects on invasion.”

They also found that dialing up the portion of BACH1 to an intermediate level, a mid-position of the dimmer, actually inhibited the cancer invasion process, as if the light became less bright while pushing the dimmer knob up.

“Our findings provide a cautionary tale when it comes to metastasis and proteins that appear to advance the cancer process—that is, we need to take a closer look at these proteins and genes and their exact role in cancer,” said Balázsi. “It’s very possible in some cases we need to inhibit them to treat cancer, and in some cases, depending on their original levels we need to increase them, or even both, yet we need much more investigation to help determine anything conclusive.”