63
enhance the immune system and therefore indirectly reducing tumorigenesis as well
as tumor growth in animals (Tomé et al. 2015). Similarly, prolonged survival due to
treatment with nutraceuticals and drugs derived from polysaccharides have been
documented in numerous controlled clinical trials (Ina et al. 2016). Antiinflammatory and anti-allergy effects of some polysaccharide products have also
been demonstrated in controlled human and animal studies. Plant polysaccharides
with antitumor effect can function in tumorigenesis of various cell lines mainly
through the suppression of tumor growth, apoptosis induction, enhancement of
immune function and coordination of chemotherapy drugs (Tian et al. 2013).
Microbial polysaccharides (which are mainly derived from bacteria and fungi)
with significant antitumor activity have also been found. They can be used for suppressing the growth of tumor cells, induction of apoptosis, immunopotentiation,
synergistic chemotherapy drugs and other ways that can produce an antitumor effect.
Polysaccharides mainly exert antitumor effects through two major mechanisms
(Pandya et al. 2018):
(i) The direct effect of polysaccharides on tumor cells.
(ii) Enhancing the immune function of the organism (indirect anti-tumour
activities)
4.7.4.1 Direct Effect of Polysaccharides on Tumor Cells
This can be effected through six different mechanisms:
(a) Direct inhibition to the growth of a tumor cell. Polysaccharides can have a
direct antitumor effect on tumor cells that present cytotoxic effects (Chen and
Huang 2018). For example, a polysaccharide obtained from the root of
Sanguisorba officinalis L (sowp) could suppress the growth of H22 ascites
tumor cells, prolong the survival time of ascites tumor mice, and also reduce
toxicity to normal cells (Friedman 2016; Zong et al. 2012).
(b) Induction of tumor cell apoptosis. Apoptosis is a spontaneous, active cell death
process that is prevalent in multicellular organisms and the inherent mechanism
of the relative stability of the cells to maintain the number of cells. Obstacles or
abnormalities to this mechanism may lead to a tumor or other lesions. Induction
of tumor cell apoptosis is therefore a novel method of cancer treatment. The
mechanism of tumor cell apoptosis induced by polysaccharide is by inhibiting
the telomerase activity and inducing the apoptosis of tumor cells through a
change in the mitochondrial membrane potential, blocking of the cell cycle,
affecting the manifestation of apoptosis-related genes, regulation of the expression and activity of Caspase protease (Chen and Huang 2018; Zong et al. 2012).
(c) Inhibition of tumor angiogenesis. The control of tumor-associated angiogenesis
is a promising mechanism for limiting cancer progression since angiogenesis is
vital for tumor growth and metastasis (Weis and Cheresh 2011). Solid tumor
growth and metastasis have a close relationship with the formation of neovascularization. New blood vessels provide adequate nutritional supply to the
4 Bioactive Carbohydrates, Biological Activities, and Sources
enhance the immune system and therefore indirectly reducing tumorigenesis as well
as tumor growth in animals (Tomé et al. 2015). Similarly, prolonged survival due to
treatment with nutraceuticals and drugs derived from polysaccharides have been
documented in numerous controlled clinical trials (Ina et al. 2016). Antiinflammatory and anti-allergy effects of some polysaccharide products have also
been demonstrated in controlled human and animal studies. Plant polysaccharides
with antitumor effect can function in tumorigenesis of various cell lines mainly
through the suppression of tumor growth, apoptosis induction, enhancement of
immune function and coordination of chemotherapy drugs (Tian et al. 2013).
Microbial polysaccharides (which are mainly derived from bacteria and fungi)
with significant antitumor activity have also been found. They can be used for suppressing the growth of tumor cells, induction of apoptosis, immunopotentiation,
synergistic chemotherapy drugs and other ways that can produce an antitumor effect.
Polysaccharides mainly exert antitumor effects through two major mechanisms
(Pandya et al. 2018):
(i) The direct effect of polysaccharides on tumor cells.
(ii) Enhancing the immune function of the organism (indirect anti-tumour
activities)
4.7.4.1 Direct Effect of Polysaccharides on Tumor Cells
This can be effected through six different mechanisms:
(a) Direct inhibition to the growth of a tumor cell. Polysaccharides can have a
direct antitumor effect on tumor cells that present cytotoxic effects (Chen and
Huang 2018). For example, a polysaccharide obtained from the root of
Sanguisorba officinalis L (sowp) could suppress the growth of H22 ascites
tumor cells, prolong the survival time of ascites tumor mice, and also reduce
toxicity to normal cells (Friedman 2016; Zong et al. 2012).
(b) Induction of tumor cell apoptosis. Apoptosis is a spontaneous, active cell death
process that is prevalent in multicellular organisms and the inherent mechanism
of the relative stability of the cells to maintain the number of cells. Obstacles or
abnormalities to this mechanism may lead to a tumor or other lesions. Induction
of tumor cell apoptosis is therefore a novel method of cancer treatment. The
mechanism of tumor cell apoptosis induced by polysaccharide is by inhibiting
the telomerase activity and inducing the apoptosis of tumor cells through a
change in the mitochondrial membrane potential, blocking of the cell cycle,
affecting the manifestation of apoptosis-related genes, regulation of the expression and activity of Caspase protease (Chen and Huang 2018; Zong et al. 2012).
(c) Inhibition of tumor angiogenesis. The control of tumor-associated angiogenesis
is a promising mechanism for limiting cancer progression since angiogenesis is
vital for tumor growth and metastasis (Weis and Cheresh 2011). Solid tumor
growth and metastasis have a close relationship with the formation of neovascularization. New blood vessels provide adequate nutritional supply to the
4 Bioactive Carbohydrates, Biological Activities, and Sources