LAUSR

Within the short span of just 3 weeks in June and July, 2020, the mammary gland biology community found itself mourning the passing of 2 friends and eminent scientists in the field – Drs. Zena Werb and Gil Smith. Both Zena and Gil had contributed their entire lifetime to decades of pioneering work studying the normal and neoplastic mammary gland and its biology. In fact, their combined careers amounted to over 100 years – a century – all devoted to studying the basis of how cells communicate, identify and evolve, and function in the mammary gland both in the normal state and in the progression to cancer. The legacy that Zena and Gil leave behind goes beyond anything that can be captured in words. Both were prolific scientific authors – a search of Pubmed limited by the term “and mammary” highlights that their combined authorship tally was over 270 peer-reviewed publications when confined by that one keyword. Not only were they prolific, they were also impactful – both of their laboratories consistently published in the highest tier of journals over many years, right up until their passing, and their findings extended to fields far beyond those related to the mammary gland. Zena and Gil were true friends and colleagues to many within the mammary gland biology community. As mentors they, within their laboratories, gave rise to multiple generations of cell biologists, just like progenitor cells within the mammary gland would. Many of those trainees are now leaders within the field and have gone on to give rise to their own lineages. At the same time, both Gil and Zena became part of a local niche in the mammary gland and developmental biology communities at their institutions; both were known for their enthusiasm to collaborate and to foster ideas within their local microenvironment. They were widely-respected legends within their respective institutions of the University of California, San Francisco, and the National Institutes of Health, and across their local regions. Yet the ideas they consistently seeded also spread so much further afield across the globe, just like how the mammary epithelium expands into the gland. Both were cherished attendees and presenters at meetings including the Gordon Research Conference onMammary Gland Biology, which has recently granted the opportunity to recognize Zena and Gil’s contributions in a joint tribute session for the 50th anniversary meeting in 2021. In retrospect, Zena and Gil’s work co-evolved over decades, and tracked alongside each other, almost like basal and luminal cells might. The resulting signals they discovered gave cues and guidance for how we all now study the gland. As a case in point, both scientists changed the way we now look at the interaction of epithelial cells with each other [1, 2] at different stages of development, as well as the surrounding microenvironment [3, 4]. Both incorporated and assessed the importance of the endocrine and paracrine environment [5, 6]. And both developed, used and shared technologies to study the mammary gland in clever ways – particularly through the use of transplantation and cell labeling [7, 8]. Many Board members were fortunate enough to have trained with, to have learned techniques from, or to have collaborated with, Zena and/or Gil over their careers and there is no doubt their legacy will live on. Following are some of the many tributes from our Editorial Board members: