61 Breast cancer remains the most common cancer among women, with around 70% of cases being oestrogen receptor positive. These cancers are typically treated with hormone blocking therapies such as tamoxifen or aromatase inhibitors, which work by cutting off the tumour’s supply of oestrogen. While these treatments can be highly effective in the early stages, up to 40% of patients eventually relapse as their cancers develop resistance. The findings were published in the International Journal of Cancer. Now, researchers have shed light on a previously underexplored cause of this resistance, offering fresh hope for new treatments. The new study highlights the role of long noncoding RNAs (lncRNAs), which are genetic molecules that do not produce proteins but instead regulate how genes behave, in helping breast cancer cells evade the effects of hormone therapy. The research focuses on how these lncRNAs interact with the unfolded protein response (UPR), a stress response system inside cells. Normally, the UPR helps cells cope with the build up of misfolded proteins. In breast cancer cells, however, the same process can be hijacked to protect tumours from treatment, allowing them to survive and grow even when oestrogen is blocked. Scientists found that certain lncRNAs can directly alter the behaviour of oestrogen receptors or activate alternative growth signals when the main hormone pathway is blocked. Others help rewire cancer cell metabolism, making them more adaptable under treatment stress. These lncRNAs not only sustain cancer cell growth but can also trigger genetic and biochemical changes that make tumours far less responsive to hormone therapy. Some of the key lncRNAs identified in the study include H19, MALAT1, UCA1, and GAS5, each playing different roles in maintaining cancer cell survival. For example, H19 promotes cell growth by influencing the activity of major survival pathways, while MALAT1 affects gene expression linked to cell division and stress responses. UCA1 fuels resistance by activating growth promoting signalling networks, and GAS5, which normally helps suppress tumours, is often reduced in resistant cancers. The interplay between lncRNAs and the UPR appears to be a crucial driver of therapy resistance. This connection means that targeting these RNAs could make cancer cells more vulnerable to existing hormone treatments. Laboratory experiments have already shown that blocking specific lncRNAs can restore sensitivity to tamoxifen in previously resistant cells. The study also points to the potential of new RNA based therapies, such as antisense oligonucleotides, which are designed to silence harmful lncRNAs. These treatments are already being developed for other diseases, and researchers believe they could be adapted to help patients with resistant breast cancer. While these findings will need further validation in clinical trials, they represent a significant step towards personalised treatment for breast cancer. By identifying and targeting the genetic switches that help tumours outsmart hormone therapy, doctors could one day prevent resistance from developing in the first place, improving survival rates and quality of life for thousands of women each year.