Obesity is correlated with elevated leptin levels, localized inflammation within adipose tissue and subsequent insulin resistance results in hyperinsulinemia. Obesity and metabolic dysfunction may also lead to an accumulation of immuno-suppressive cells in an attempt to counter obesity-associated inflammation.
Insulin and leptin are potent stimulators of cancer growth but are rarely measured when assessing cancer prognosis or progression. That has important implications for cancer patients.
Recent research has shown that obesity interferes with many cancer treatments, including immunotherapy. With the science behind metabo-oncology revealing the profound impact obesity and metabolic dysfunction have on cancer patients’ treatments and outcomes, this omission is likely to change.
From Murphy et al., 2018, Cutting Edge: Elevated Leptin during Diet-Induced Obesity Reduces the Efficacy of Tumor Immunotherapy:
“Various malignancies are reproducibly cured in mouse models, but most cancer immunotherapies show objective responses in a fraction of treated patients. One reason for this disconnect may be the use of young, lean mice lacking immune-altering comorbidities present in cancer patients. Although many cancer patients are overweight or obese, the effect of obesity on antitumor immunity is understudied in preclinical tumor models.
“We examined the effect of obesity on two immunotherapeutic models: systemic anti–CTLA-4 mAb and intratumoral delivery of a TRAIL-encoding adenovirus plus CpG. Both therapies were effective in lean mice, but neither provided a survival benefit to diet-induced obese BALB/c mice. Interestingly, tumor-bearing leptin-deficient (ob/ob) obese BALB/c mice did respond to treatment. Moreover, reducing systemic leptin with soluble leptin receptor:Fc restored the antitumor response in diet-induced obese mice. These data demonstrate the potential of targeting leptin to improve tumor immunotherapy when immune-modulating comorbidities are present.”
From Quail et al., 2017, Obesity alters the lung myeloid cell landscape to enhance breast cancer metastasis through IL5 and GM-CSF:
“Obesity is associated with chronic, low-grade inflammation, which can disrupt homeostasis within tissue microenvironments. Given the correlation between obesity and relative risk of death from cancer, we investigated whether obesity-associated inflammation promotes metastatic progression.
“We demonstrated that obesity causes lung neutrophilia in otherwise normal mice, which is further exacerbated by the presence of a primary tumor. The increase in lung neutrophils translates to increased breast cancer metastasis to this site, in a GM-CSF- and IL5-dependent manner. Importantly, weight loss is sufficient to reverse this effect and reduce serum levels of GM-CSF and IL5 in both mouse models and humans. Our data indicate that special consideration of the obese patient population is critical for effective management of cancer progression.”