Exopolysaccharides extracted from Parachlorella kessleri inhibit colon carcinoma growth in mice via stimulation of host antitumor immune responses

PLoS One. 2017 Apr 5;12(4):e0175064. doi: 10.1371/journal.pone.0175064. eCollection 2017.

Abstract

The newly purified extracellular polysaccharides (exopolysaccharides) from Parachlorella kessleri (PCEPS) were evaluated on their antitumor and immunomodulatory effects in cell culture and mouse colon carcinoma peritoneal dissemination model. In two-dimensional cell culture, the PCEPS treatment inhibited cell growth of both murine and human colon carcinoma cells in a dose- and time-dependent manner. In contrast, the growth of mouse splenocytes (SPLs) and bone marrow cells (BMCs) were stimulated by the treatment with PCEPS. The treatment with PCEPS also increased specific subpopulations of the cells in BMCs: antigen presenting cells (CD19+ B cells, 33D1+ dendritic cells and CD68+ macrophage) and CD8+ cytotoxic T cells. In three-dimensional spheroid culture, spheroid growth of CT26 cells co-cultured with HL-60 human neutrophilic promyeloblasts and Jurkat cells (human lymphoblasts), but not THP-1 human monocyte/macrophage was significantly attenuated by PCEPS treatment. In a mouse CT26 colon carcinoma peritoneal dissemination model, intraperitoneal injection of PCEPS (10 mg/kg, twice per week) significantly attenuated the growth of CT26 colon carcinoma in syngeneic mice. The present study suggests that PCEPS inhibits colon carcinoma growth via direct cell growth inhibition and a stimulation of the host antitumor immune responses. Taken together, the current study suggests that exopolysaccharides derived from Parachlorella kessleri contain significant bioactive materials that inhibit colon carcinoma growth.

MeSH terms

  • Animals
  • Antineoplastic Agents / therapeutic use*
  • Bone Marrow Cells / drug effects
  • Cell Line, Tumor
  • Chlorella / chemistry*
  • Chlorophyta
  • Colonic Neoplasms / drug therapy*
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Immunologic Factors / therapeutic use*
  • Mice
  • Mice, Inbred BALB C
  • Plant Extracts / therapeutic use*
  • Polysaccharides / therapeutic use*
  • Spleen / cytology
  • Spleen / drug effects

Substances

  • Antineoplastic Agents
  • Immunologic Factors
  • Plant Extracts
  • Polysaccharides

Grants and funding

This study was supported by funds from Kansas State University Johnson Cancer Research Center 2011JCRCEQ (MT), 2014CRA (ZG and MT), 2015CRA (JH, HH, AN and MT), 2016CRA (HH and MT), College of Veterinary Medicine Dean's funds 2010CVM-EQ (MT), and NIH grant P20 RR017686 (MT). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.