Kefir, a fermented milk product, exhibits
anti‑tumoral activity in vivo; yet its mechanism of action
remains elusive. Recent studies have focused on the
mechanism of action of kefir on cancer cells in vitro. The
current study aims at examining the effect of kefir on cell
survival, proliferation, and motility of colorectal cancer (CRC )
cells. Kefir's anti‑cancer potential was tested on CRC cell
lines, Caco‑2 and HT‑ 29, through cytotoxicity, proliferation,
and apoptotic assays. The expression of certain genes
involved in proliferation and apoptosis was measured using
reverse transcriptase‑polymerase chain reaction (RT‑ PCR )
and western blotting. To assess the effect of kefir on cancer
metastasis, wound‑healing and time‑lapse movies, in addition
to collagen‑based invasion assay, were used. The results show
that cell‑free fractions of kefir exhibit an anti‑proliferative
effect on Caco‑2 and HT‑ 29 cells. Analysis of DNA content
by flow cytometry revealed the ability of kefir to induce cell
cycle arrest at the G1 phase. Kefir was also found to induce
apoptosis, as seen by cell death ELI SA. Results from RT‑ PCR
showed that kefir decreases the expression of transforming
growth factor α (TGF‑α); a nd t ransforming g rowth
factor‑β1 (TGF‑β1) in HT‑ 29 cells. Western blotting results
revealed an upregulation in Bax:Bcl‑2 ratio, confirming
the pro‑apoptotic effect of kefir, and an increase in p53
independent‑p21 expression upon kefir treatment. MMP
expression was not altered by kefir treatment. Furthermore,
results from time‑lapse motility movies, wound‑healing, and
invasion assays showed no effect on the motility of colorectal
as well as breast (MCF‑7 and MB‑MDA‑231) cancer cells
upon kefir treatment. Our data suggest that kefir is able to
inhibit the proliferation and induce apoptosis in HT‑ 29 and
Caco‑2 CRC cells, yet it does not exhibit a significant effect
on the motility and invasion of these cells in vitro.