Bacterial Antigens Reduced the Inhibition Effect of Capsaicin on Cal 27 Oral Cancer Cell Proliferation

Abstract

Oral cancer is a major global health problem with high incidence and low survival rates. The oral cavity contains biofilms as dental plaques that harbour both Gram-negative and Gram-positive bacterial antigens, lipopolysaccharide (LPS) and lipoteichoic acid (LTA), respectively. LPS and LTA are known to stimulate cancer cell growth, and the bioactive phytochemical capsaicin has been reported to reverse this effect. Here, we tested the efficacy of oral cancer chemotherapy treatment with capsaicin in the presence of LPS, LTA or the combination of both antigens. LPS and LTA were administered to Cal 27 oral cancer cells prior to and/or concurrently with capsaicin, and the treatment efficacy was evaluated by measuring cell proliferation and apoptotic cell death. We found that while capsaicin inhibits oral cancer cell proliferation and metabolism (MT Glo assay) and increases cell death (Trypan blue exclusion assay and Caspase 3/7 expression), its anti-cancer effect was significantly reduced on cells that are either primed or exposed to the bacterial antigens. Capsaicin treatment significantly increased oral cancer cells’ suppressor of cytokine signalling 3 gene expression. This increase was reversed in the presence of bacterial antigens during treatment. Our data establish a rationale for clinical consideration of bacterial antigens that may interfere with the treatment efficacy of oral cancer.

ML218 HCl Is More Efficient Than Capsaicin in Inhibiting Bacterial Antigen-Induced Cal 27 Oral Cancer Cell Proliferation

“…We recently reported that the combination of bacterial antigens, lipoteichoic acid (LTA) and lipopolysaccharide (LPS), resulted in increased proliferation of the oral cancer cell Cal 27, but not SCC4, SCC9 and SCC25, compared to stimulation with LPS alone [2]. We then developed an in vitro assay to measure the efficacy of drug treatment on Cal 27 in the presence of bacterial antigens, and examined the effect of capsaicin, which is known to induce apoptosis in several cancers [3]. The bacterial antigens LPS and LTA decreased the anti-cancer efficacy of capsaicin, both for antigenic stimulation given prior to and concurrently with this drug [3].…”

“…We then developed an in vitro assay to measure the efficacy of drug treatment on Cal 27 in the presence of bacterial antigens, and examined the effect of capsaicin, which is known to induce apoptosis in several cancers [3]. The bacterial antigens LPS and LTA decreased the anti-cancer efficacy of capsaicin, both for antigenic stimulation given prior to and concurrently with this drug [3].…”

“…Xiang et al reported ML218 as a T-type voltage-gated calcium channel [Cav 3.2 and Cav 3.3] inhibitor [11]. This raised the question as to whether substituting ML218 HCl (the commercially available form of ML218) for capsaicin in our drug treatment protocol [3] would lower Cal 27 oral cancer viability.…”

“…We hypothesized that ML218 HCl could be more effective than capsaicin in reducing bacterial antigen (LPS + LTA)-induced oral cancer cell proliferation and, therefore, the anticancer effects of ML218 HCl would be affected less by the presence of bacterial antigens compared to capsaicin (which we previously investigated [3]). This study focuses on investigating (a) the effect of ML218 HCl on Cal 27 oral cancer cell proliferation in the presence and absence of oral bacterial antigens, and (b) the effect of ML218 HCl on Cal 27 oral cancer cell proliferation factors SOCS3, EGFR, STAT3, PIK3 and TNFα, and apoptotic pathways in the presence and absence of oral bacterial antigens.…”

“…This study focuses on investigating (a) the effect of ML218 HCl on Cal 27 oral cancer cell proliferation in the presence and absence of oral bacterial antigens, and (b) the effect of ML218 HCl on Cal 27 oral cancer cell proliferation factors SOCS3, EGFR, STAT3, PIK3 and TNFα, and apoptotic pathways in the presence and absence of oral bacterial antigens. Throughout this report, we included capsaicin data (that was previously published) [3] in each figure for ease of comparison between ML218 HCl and capsaicin treatment groups.…”