Anti-estrogenic therapies can suppress the growth of cancer that does not express estrogen receptors; when combined with immune checkpoint inhibitor therapies, they halt tumor progression in mice models. Estrogen, a group of female hormones, is known to be involved in cancer progression, especially breast cancer. About 75% of breast cancers are estrogen-sensitive: they express the hormone receptor estrogen receptor α (ERα), and estrogen promotes tumor growth. Surprisingly, estrogen has been observed to promote tumor growth in ERα-negative cancers, such as triple-negative breast cancer (TNBC), for reasons that are not fully understood. The researchers analyzed patient data from The Cancer Genome...