Forcing Resistant Prostate Cancer Back into Treatment Range: eIF4E Could Help

Prostate cancer often becomes dangerous because the tumor cells can change their identity to escape treatment. At first, most prostate cancers are “luminal”: they depend on the androgen receptor (AR), a protein that acts like a growth switch turned on by male hormones. Drugs that block this receptor, such as enzalutamide, usually work well at the start. Over time, though, some tumors switch to a “basal” state. These basal cells use different proteins (basal keratins), rely less on AR, and stop responding to hormone‑blocking drugs. This ability to change identity is called lineage plasticity and is a major reason why advanced prostate cancer is so hard to control.

A new study shows that a small but powerful control point inside the cell, called the eIF4E cap‑binding domain, helps keep tumors in this resistant basal state. eIF4E is a protein that helps start the process of reading messenger RNA and making new proteins. The “cap‑binding domain” is the part that grabs the protective cap on mRNA molecules. The researchers found that this domain does not just increase protein production in general; it selectively boosts a specific set of messages that define the basal identity, especially those for basal keratins.

To test this, the team used a new drug, PF‑07293623, which sticks to eIF4E’s cap‑binding site and blocks it. In aggressive, AR‑low prostate cancer cells and tumors in mice, the drug strongly slowed growth. It cut overall protein production by about 40 percent, but the most important effect was selective: the cells stopped making key basal keratin proteins even though the mRNA for those keratins was still present. This showed that the drug was turning down translation of specific messages, not silencing the genes themselves.

At the same time, something helpful happened: the androgen receptor itself went up. AR protein levels increased several fold, especially in the nucleus where AR works, even though AR mRNA did not change. The researchers traced this to two enzymes, BAP1 and OTUD3, whose protein levels rose after treatment. These enzymes remove “destroy me” tags from AR, so the receptor lasts longer instead of being broken down. When BAP1 or OTUD3 were blocked, the drug could no longer raise AR levels, confirming that this stabilization is a key part of the effect.

Put together, blocking the eIF4E cap‑binding domain pushes basal, drug‑resistant prostate cancer cells back toward a more luminal, AR‑dependent state. In mice with basal tumors that did not respond to enzalutamide alone, adding PF‑07293623 made the tumors shrink. The combination increased AR in the tumors, reduced cell division, and increased cell death, without obvious side effects. This suggests that the drug can “re‑educate” resistant cancers so that standard hormone therapies can work again.

Source.