Thermal/ultrasound-triggered release of liposomes loaded with Ganoderma applanatum polysaccharide from microbubbles for enhanced tumour ablation

The effectiveness of thermal ablation for the treatment of liver tumours is limited by the risk of incomplete ablation, which can result in residual tumours. Herein, an enhancement strategy is proposed based on the controlled release of Ganoderma applanatum polysaccharide (GAP) liposome-microbubble complexes (GLMCs) via ultrasound (US)-targeted microbubble destruction (UTMD) and sublethal hyperthermic (SH) field. GLMCs were prepared by conjugating GAP liposomes onto the surface of microbubbles via biotin-avidin linkage. In vitro, UTMD promotes the cellular uptake of liposomes and leads to apoptosis of M2-like macrophages. Secretion of arginase-1 (Arg-1) and transforming growth factor-beta (TGF-β) by M2-like macrophages decreased. In vivo, restriction of tumour volume was observed in rabbit VX2 liver tumours after treatment with GLMCs via UTMD in GLMCs + SH + US group. The expression levels of CD68 and CD163, as markers of tumour-associated macrophages (TAMs) in the GLMCs + SH + US group were reduced in liver tumour tissue. Decreased Arg-1, TGF-β, Ki67, and CD31 factors related to tumour cell proliferation and angiogenesis was evident on histological analysis. In conclusion, thermal/US-triggered drug release from GLMCs suppressed rabbit VX2 liver tumour growth in the SH field by inhibiting TAMs, which represents a potential approach to improve the effectiveness of thermal ablation.

Effect of Ganoderma applanatum polysaccharides on MAPK/ERK pathway affecting autophagy in breast cancer MCF-7 cells

Fungal polysaccharides have become hotspots in the field of health foods due to their antitumor activity in recent years. In this experiment, antitumor effect of the medicinal fungus Ganoderma applanatum polysaccharide (GAP) was investigated in human breast cancer MCF-7 cells, as well as the molecular mechanism of its effect on autophagy. Results showed that GAP contains three polysaccharides with molecular weights of 6.36 × 10⁵ Da, 4.25 × 10⁵ Da, and 2.53 × 10⁵ Da and which composed of rhamnose, glucose, arabinose, fucose in the molar ratio of 1:22:16.1:3.2. GAP inhibited the proliferation and migration of MCF-7 cells in a time-dose-dependent manner, the maximum inhibition rate reached 50.2% at 500 μg/mL in 48 h. Flow cytometry analysis showed that GAP could induce apoptosis, treatment of cells with GAP could result in up-regulation of gene and protein levels of autophagy-associated markers LC3 and Beclin-1; addition of autocrine late inhibitor CQ significantly raised the protein expression level of LC3II. The mitogen-activated protein kinases (MAPK) signaling pathway was not only related to the apoptotic pathway but also to the autophagy pathway; Western blot analysis showed that MAPK signaling pathway is involved in GAP-induced autophagy in MCF-7 cells. Detection of the relevant signaling pathway protein showed that the expression of p-ERK1/2 protein was down-regulated, however the expression of p-p38 and p-JNK protein was up-regulated. These results indicate that GAP could induce early autophagy in MCF-7 cells via the MAPK/ERK pathway. In conclusion, GAP showed strong antitumor activity by inducing apoptosis and autophagy through MAPK signaling pathway in MCF-7 cells, suggesting the molecular mechanism of fungal polysaccharide on its antitumor activity.