Treatment with adjuvant tamoxifen has proven to increase breast cancer patient’s survival rate. However, it is not without considerable side effects. Patients on tamoxifen can, for example, experience hot flashes, changes in bone density and fatigue.

To try to understand what causes these unwelcome side effects, a research group from the University of California Los Angeles treated 50 mice with tamoxifen and monitored their response over 28 days. Their results were published in the journal Neuroscience in March 2021.

Tamoxifen alters temperature, bone density and activity
Mice treated with tamoxifen were found to display altered thermoregulation, increased bone density and decreased movement. Single-cell RNA sequencing also revealed widespread gene expression changes in both the hypothalamus and preoptic area. The changes in gene expression are known to be dependent on estrogen receptor alpha (ERα).

Alongside thermal imaging and telemetry measurements, Star-Oddi’s DST nano-T loggers were used to monitor tail skin temperature every 5 minutes. This data showed consistent 24hr averages when compared to telemetry data.

A first step to improving treatment
From the results it was clear that tamoxifen treatment in mice mimics some of the key side effects that human patients experience. The authors suggest the hypothesis that tamoxifen treatment may alter thermoregulation, activity and bone density through changes in ERα signalling in the brain.

These results are a positive first step to improving tamoxifen treatment in humans in the future.