TNF and gastric cancer: Stimulate splenocyte proliferation, promoted anti-inflammatory cytokines (IL-2, IL-4 and IL-10) production, inhibited pro-inflammatory cytokine (IL-6 and TNF-α) secretion, augment the killing activity of NK cells and cytotoxic T lymphocytes (CTL), and increase phagocytotic function of macrophages in gastric cancer rats