By increasing the peripheral white blood cells count, thymus and spleen indexes, the production of serum cytokines such as IL-2, IL-4, and TNF-α, and promoting splenocytes proliferation, the polysaccharide fraction of Portulaca oleracea L. inhibited tumor growth in N-methyl-N’-nitro-N-nitrosoguanidine-induced gastric cancer rats [139]. Here, TNF is linked to gastric cancer.