Identification of senescence-associated drivers of tumour growth and progression using a novel microarray platform

Senescence and the senescence associated secretory phenotype (SASP) are implicated in promoting early tumorigenesis but due to the complexity of SASP it has been difficult to identify the responsible factors. We used canonical SASP factors on our microenvironment microarray (MEMA) platform to systematically identify SASP-associated drivers of tumorigenesis in breast and lung cancer cells. We found multiple SASP factors enhanced the proliferation and overall cell numbers for both lung and breast cells grown on the MEMA, and that there was significant overlap in SASP-associated growth-promoting factors between the two different cell types. We validated the ability of several factors, including IL-6, TGF-β and EGF, to drive growth in <i>in vitro</i> assays. Interestingly, these factors were effective in driving growth and survival in cells that were altered (either immortalized or fully transformed) but not in normal cells and impacted breast cells differently depending on the age of the patient. RNAseq identified upregulation of wound-healing and stem-cell programs in SASP factor-treated cells. Many of these same SASP factors were present in conditioned media collected from senescent cells, which enhanced the growth of both lung and breast cancer cells, and inhibitors of the specific SASP factors partially reduced growth. Similarly, targeted inhibition of EGF partially reduced lung tumour growth in xenografts when senescent but not normal fibroblasts were co-implanted. Our findings have identified core SASP drivers of tumorigenesis and suggest that effective tumorigenesis driven by SASP is multifactorial and requires alterations in the target cells to achieve maximal response.