Circulating tumor cells share RNA modules with early embryo trophectoderm and with metastatic cancer

Metastasis is the primary cause of cancer-related deaths, accounting for an estimated 66% to 90% of fatalities [1]. It is a multistep process involving the dissemination of circu- lating tumor cells (CTCs) and their colonization of distant organs [2, 3]. A higher number of detected CTCs in cancer patients is associated with shorter survival [4]. We analyzed 544 single-cell RNA sequencing (scRNA- seq) profiles of bona fide CTCs, identified as keratin- positive and aneuploid, from over 3,000 putative CTC profiles available in public databases, as detailed in Sup- plementary Table S1. Most of the CTCs originated from patients with breast cancer (n = 502, 92.3%), while a smaller number were derived from patients with prostate cancer (n = 42).