Inactivation of the WASF3 gene suppresses invasion and metastasis of breast cancer cells. WASF3 function is regulated through a protein complex that includes the NCKAP1 and CYFIP1 proteins. Here we report that silencing NCKAP1 destabilizes the WASF3 complex, resulting in a suppression of the invasive capacity of breast, prostate and colon cancer cells. In an in vivo model of spontaneous metastasis in immunocompromized mice, loss of NCKAP1 also suppresses metastasis. Activation of the WASF protein complex occurs through interaction with RAC1, and inactivation of NCKAP1 prevents the association of RAC1 with the WASF3 complex. Thus, WASF3 depends on NCKAP1 to promote invasion and metastasis. Here we show that stapled peptides targeting the interface between NCKAP1 and CYFIP1 destabilize the WASF3 complex and suppress RAC1 binding, thereby suppressing invasion. Using a complex-disrupting compound identified in this study termed WANT3, our results offer a mechanistic proof of concept to target this interaction as a novel approach to inhibit breast cancer metastasis.

Activation of the WASF3 protein by extracellular stimuli promotes actin cytoskeleton reorganization and facilitates cancer cell invasion, whereas WASF3 depletion suppresses invasion and metastasis. In quiescent cells, the interaction between WASF3 and a complex of proteins including CYFIP1 acts as a conformational restraint to prevent WASF3 activation. Therefore, we took advantage of this endogenous regulatory mechanism to investigate potential sites that disrupt WASF3 function. Here, we show that genetic knockdown of CYFIP1 in cancer cells led to the destabilization of the WASF3 complex, loss of WASF3 function, and suppressed invasion. Based on existing crystallographic data, we developed stapled peptides, referred to as WASF Helix Mimics (WAHM), that target an α-helical interface between WASF3 and CYFIP1. Treatment of highly invasive breast and prostate cancer cells with WAHM inhibitor peptides significantly reduced motility and invasion in vitro. Mechanistic investigations revealed that these inhibitors suppressed the interaction between Rac and the WASF3 complex, which has been shown to promote cell migration. Furthermore, peptide-mediated inhibition of WASF3 also resulted in the dysregulation of known downstream targets such as MMP-9 and KISS1. Finally, we demonstrate that this invasive phenotype is specific to WASF3 as depletion of WASF1 and WASF2, which can also bind to CYFIP1, did not affect invasion. Collectively, our findings suggest that targeting WASF3 function with WAHM peptides could represent a promising therapeutic strategy for preventing tumor invasion and metastasis.

BACKGROUND Reports in 2015 showed that premature birth rate in the United States increased when compared to 2014 data, and this was the first increment since 2007. Major complications of prematurity and birth weight abnormalities are well known, but other complications including mental health abnormalities require more investigation to understand their association well. OBJECTIVES We aimed in this study to determine if prematurity and birth weight abnormalities including very low birth weight (VLBW) and low birth weight (LBW) are associated with depression among United States children aged between six and seventeen years old. ​ DESIGN/METHODS This is a cross sectional study using data from the National Survey of Children’s Health (NSCH) 2011–2012. When we applied our selection criteria, 84,182 children out of the total 95,677 NSCH population were selected. Our exclusion criteria were: age less than six years, child’s history of cerebral palsy, and mental retardation. Multivariable logistic regression was done to control for confounding effects when studying the association of prematurity, birth weight abnormalities and depression. ​ RESULTS Our results reveal that 3.6% of our population had history of depression, 11% were born prematurely, 7.4% had low birth weight, and 1.5% had very low birth weight. Depression was more frequent in children who were born prematurely (prevalence 4.3%) when compared to children born at term. Different models were built to analyze the association between prematurity, birth weight abnormalities and depression. There was no detectable statistically significant association when controlling for demographic data (age, gender, race, family structure) and mental health risk factors (parental poor mental health, chronic health conditions) as well as other factors. Results reveal that children who had chronic health conditions or had adverse family experiences have greater odds of having depression. On the other hand, African-American, male, and younger (6–11 years old) children have lower odds of depression. ​ CONCLUSION Further longitudinal studies are required to establish a causal relationship of behavioral and psychological complications, and to determine the biological mechanisms of brain development that could be associated with depression among premature infants or those who have birth weight abnormalities.