The serological responses to acute exercise in humans reduce cancer cell growth in vitro: A systematic review and meta‐analysis

• Published in: Physiological reports Vol. 8; no. 22; pp. e14635 - n/a
• Main Authors: Orange, Samuel T., Jordan, Alastair R., Saxton, John M.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.11.2020; John Wiley and Sons Inc; Wiley
• Subjects: Bias; biomarkers; Biomarkers, Tumor - blood; Biomarkers, Tumor - standards; Cancer; cancer prevention; Cell culture; Cell growth; Colon; Exercise; exercise physiology; Humans; Medical research; Meta-analysis; Neoplasms - blood; Neoplasms - physiopathology; p53 Protein; physical activity; Physical fitness; Physiology; Review; Reviews; Serology; serum; Tumor Suppressor Protein p53 - blood; Tumor Suppressor Protein p53 - standards; Weightlifting; cancer prevention; serum; biomarkers; exercise physiology; physical activity
• ISSN: 2051-817X
• DOI: 10.14814/phy2.14635

We systematically reviewed and meta‐analyzed the effects of acute exercise‐conditioned serum on cancer cell growth in vitro. Five literature databases were systematically searched for studies that measured cancer cell growth after exposure to human sera obtained before and immediately after an acute bout of exercise. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were pooled using a three‐level random‐effects model. Meta‐regressions were also performed with participant age and disease status, exercise type, cell line TP53 status, and serum incubation time entered as covariates. Seven studies met the inclusion criteria encompassing a total of 21 effect estimates and 98 participants. Exercise‐conditioned serum significantly reduced cancer cell growth compared with preexercise serum (SMD = −1.23, 95% CI: −1.96 to −0.50; p = .002; I2 = 75.1%). The weighted mean reduction as a percentage of preexercise values was 8.6%. The overall treatment effect and magnitude of heterogeneity were not statistically influenced by any covariate. There were concerns regarding the risk of bias within individual studies and Egger's test of the intercept showed evidence of small study effects (β = −3.6, p = .004). These findings provide in vitro evidence that the transient serological responses to acute exercises reduce cancer cell growth, although many questions remain regarding the underlying mechanistic pathways and potential effect modifiers. To strengthen this evidence‐base, future studies should seek to reduce the risk of bias by using more rigorous experimental designs, and consider using 3D cell culture models to better replicate in vivo tumor conditions. PROSPERO registration: CRD42020161333. This systematic review and meta‐analysis showed that exercise‐conditioned serum significantly reduces in vitro cancer cell growth. This finding provides preliminary evidence that acute exercise‐induced modulations in serum markers may, at least in part, explain the link between regular physical activity and reduced cancer risk.