Milk represents a unique source of nutrients and biologically active components that act in synergy, as well as independently. Emerging evidence indicates that the protein component of milk represents a variety of biologically active proteins/peptides that function as anti-hypertensive agents, antimicrobial factors, food intake modifiers and immune regulatory factors [8
]. Interestingly, many bioactive peptides are inactive within their parent milk proteins, and upon release during digestion or food processing, they may act as regulatory compounds with hormone-like activity [10
]. Additionally, there are increasing studies showing that bioactive milk peptides can be absorbed intact from the intestinal lumen into the blood circulation - these may thus serve as novel functional food ingredients or pharmaceutical agents [12
Using a proprietary enzyme digestion and buffer isolation method, we purified a group of peptides from the whey fraction of regular cow's milk and screened against a panel of kinases. In particular, this milk peptide mixture shows inhibitory effects against EGFR, VEGFR2, and IR. EGFR is often overexpressed in non-small cell lung cancer (NSCLC) and a variety of common solid tumors. EGFR signaling is generally associated with cancer invasion, metastasis, chemotherapy resistance, and poor prognosis [16
]. It has also been reported that inhibition of EGFR may lead to apoptosis in certain cancer cell lines [18
]. Gefitinib (Iressa®, AstraZeneca plc, London, UK
) and Erlotinib (Tarceva®
, Genentech, Inc., San Francisco, CA
) are examples of anti-cancer drugs targeting EGFR-TK. Interestingly, MP mixture is also able to cause significant cell death in HT29 colon cancer cells, whereas neither commercially available hydrolyzed whey proteins nor whole milk proteins exhibited the same property. This may be because most commercial hydrolyzed whey proteins contained too small amount of bioactive peptides or the process of spray drying deactivated the activity.
This novel MP mixture also inhibits insulin receptor signaling. Interestingly, mutations in daf-2
, a gene that encodes an insulin-like receptor in C. elegans
worm, have been shown to double the lifespan of the worms [19
]. The gene is known to regulate reproductive development, ageing, resistance to oxidative stress, thermotolerance, resistance to hypoxia and also resistance to bacterial pathogens [20
]. Therefore, we next tested this unique MP mixture effect on the lifespan of C. elegans
worms. Statistical analysis of the result suggested that N2 worms fed with agar containing 20 μg/ml concentration of milk peptides increased the median lifespan by 15.4% (p = 0.014). Based on these data, we hypothesize that this milk peptide mixture may be a novel supplement ingredient for anti-aging and cancer preventive regimen.
Since MP has multi-kinase inhibitory activity in the micromolar range, we first conducted toxicology studies to measure the safety of these peptides. An acute and a 28-day sub-acute toxicology study showed no apparent adverse effects in rodents following oral administration of the peptides. Encouraged by the results, we conducted an 80 subject, double blind, placebo controlled study in healthy volunteers. The main purpose was to assess the safety of the milk peptides at three escalating dosages.
The clinical analyses showed that the MP mixture did not cause significant side effects in healthy human subjects. All blood and hormonal markers remained in normal ranges. There was a mean trend toward improving insulin sensitivity as assessed using HOMAIR that warrants additional study. This could potentially have beneficial effects for individuals with insulin resistance. However, these changes were not significant due to the large variability in responses observed. Additional study evaluating the effects of these milk peptides on glucose tolerance in individuals with and without insulin resistance would help elucidate this potential effect.
Another encouraging trend was the lowering of neutrophil to lymphocyte ratio (NLR). The neutrophil-lymphocyte ratio is a general marker of immunity and inflammatory status. Research has shown that elevated NLR to be a prognostic indicator of poor chemotherapy outcomes in advanced colorectal cancer and poor survival after colorectal liver metastases [21
]. The potential impact of MP supplementation on lowering NLR could be used as a clinical nutritional intervention for these categories of cancer patients. In addition, these peptides have been shown to have in vitro
anti-EGFR and VEGFR2 activity. EGFR is commonly elevated in many advanced cancers, and VEGFR2 is considered one of the key regulators of tumor-induced angiogenesis [24
]. Together, this novel milk peptide mixture's anti-cancer and inflammatory reducing properties may be a safe, effective supplement to help cancer patients undergoing chemotherapy to obtain better clinical outcome.
In summary, preliminary experiments suggest that there may be some potentially beneficial applications of this novel MP mixture and that six weeks of human consumption appears to be safe. The limitation of this first clinical study is that the human subjects were healthy individuals. Additional clinical studies are currently underway to further elucidate the milk peptides' impact on the progression of cancer and quality of life in cancer patients.