As the main active ingredient of an ancient Chinese herb that has been widely proven to be effective in cancer treatment, some related reviews have summarized the pharmacological effects of ginsenoside Rg3 (GS-Rg3) (1–4). With more in-depth research in recent years, more anticancer mechanisms of GS-Rg3 continue to be discovered. Therefore, the present article reviews the newly discovered anticancer mechanisms of GS-Rg3, aiming to highlight the current challenges and future prospects of GS-Rg3 in the field of cancer therapy.

GS-Rg3 is a tetracyclic triterpene saponin derived from red ginseng. Due to the chiral nature of C20, GS-Rg3 exists in two isomers: 20 (S) and 20 (R), the chemical structures of which are depicted in Fig. 1. Both 20(S)-GS-Rg3 and 20(R)-GS-Rg3 are white amorphous powders. The former is soluble in cold H₂O, ethanol, methanol and acetonitrile, while the latter is only soluble in DMSO, with trace amounts being soluble in H₂O and acetonitrile (5).

Fe@Fe₃O₄ nanoparticles have been linked with GS-Rg3 to produce a nanodrug, NpRg3, which has been found to prolong the survival time of mice with dimethylnitrosamine-induced liver cancer (6) and to exhibit synergistic effects with anticancer drugs (7). These studies have demonstrated that GS-Rg3 has the potential to serve as a precursor for developing derivatives with enhanced therapeutic efficacy.

Various types of ginsenoside nanomedicines have shown potential in the treatment of different tumors, including triple-negative breast cancer (60). The in vivo delivery results of a multifunctional black phosphorus (BP) nanoreagent, BPs/G-Rg3@PLGA, demonstrated its notable therapeutic effect on lung metastases from breast cancer, along with significant biocompatibility with various organs/tissues (61). GS-Rg3-loaded carbon nanotubes have been shown to reduce IFN-γ-induced upregulation of PD-L1 in breast cancer cells, thereby decreasing the programmed cell death protein-1/PD-L1 axis in the T cell/triple-negative breast cancer cell coculture system (62). GS-Rg3 loaded on a biomimetic nanosystem has been shown to enhance the sensitivity of tumors to doxorubicin, thereby initiating antitumor immune activation and effectively combating leukemia cells harbored in the bone marrow (63). Nanoparticles constructed using graphene oxide (GO) linked with the photosensitizer, indocyanine green (ICG), folic acid and polyethylene glycol (PEG), and loaded with GS-Rg3 (PEG-GO-FA/ICG-Rg3) can inhibit the proliferation, invasion and migration of osteosarcoma cells, enhance the apoptosis and autophagy of osteosarcoma cells and suppress the stemness of osteosarcoma cell-derived cancer stem cells (64). Ursolic acid and GS-Rg3 co-loaded liposomes can significantly reduce the proliferation of liver cancer cells, while increasing the apoptotic rate and the proportion of cells in the G0/G1 phase (65). A novel nanomedicine was recently developed by combining metal-based nanoenzymes (Fe@Fe3O4) with GS-Rg3. The glycosidic chains of GS-Rg3 formed a hydrophilic layer on the outermost surface of the nanomedicine, improving biocompatibility and pharmacokinetics, thus promoting the apoptosis of cancer cells (66). These studies suggest that ginsenoside nanomedicines have great potential in the treatment of a variety of tumor types, with improved biocompatibility, targeted delivery and enhanced therapeutic efficacy.

A number of extracts from Chinese medicinal herbs are used to treat immunological issues, and immune modulation is a key mode of action of GS-Rg3. GS-Rg3 enhances cellular immunity by upregulating CD4⁺, CD4⁺/CD8⁺, IgG, IgM and IL-2, and downregulating CD8⁺ and IL-6 in a dose-dependent manner (67). This effect may be related to its stimulation of concanavalin A (ConA)-induced lymphocyte proliferation and increased levels of the Type 1 T helper (Th1)-type cytokines, IL-2 and interferon (IFN)-γ (31). Furthermore, 20(R)-GS-Rg3 promotes natural killer (NK) cell activity via activation of the MAPK/ERK pathway, suggesting that 20(R)-GS-Rg3 may be used as an activator of NK cell cytotoxicity to treat various types of cancer (68). Cyclophosphamide decreases T-bet and IFN-γ expression in the thymus and spleen, while increasing GATA-3 and IL-4 expression, thereby altering the Th1/Th2 balance and resulting in immunosuppression (69). GS-Rg3 can antagonize this effect by regulating the ratio of T lymphocyte subsets (70). For autoimmune neuroinflammation, GS-Rg3 has a minor effect on the dendritic cell production of Th17-promoting cytokines such as IL-6, IL-12/23p40 and TNFα. Specifically, it upregulates the expression of TNFα and IL-12 and downregulates the expression of IL-6. Instead, it notably reduces the induction of RAR-related orphan nuclear receptor γt expression in the CD4⁺ T cells, and therefore inhibits the differentiation of Th17 cells from their precursors (71). These finding suggest that GS-Rg3 may be a promising therapeutic agent for the treatment of Th17-related autoimmune disorders.

GS-Rg3 has two chiral isomers with notably distinct therapeutic properties. An investigation was conducted to compare the immunological response of 20(S)-GS-Rg3 and 20(R)-GS-Rg3 as adjuvants to ovalbumin (OVA). The results revealed that both 20(R)-GS-Rg3 and 20(S)-GS-Rg3 can serve as adjuvants for the immunological response induced by OVA. However, 20(R)-GS-Rg3 significantly increased OVA-specific IgG and IgG subtypes in the blood, relative to 20(S)-GS-Rg3, and was accompanied by a marked rise in serum IFN-γ and IL-5 levels (72). 20(R)-Rg3 significantly enhanced splenocyte proliferative responses to Con A, LPS and OVA as well as mRNA expression of IFN-γ, IL-12, IL-4 and IL-10 and transcription factors T-bet and GATA-3 by splenocytes when compared with the 20(S)-Rg3 (67).

GS-Rg3 has anti-fatigue properties. GS-Rg3 can increase the physical strength of older rats by increasing serum total cholesterol, triglyceride and lactate dehydrogenase concentrations, increasing superoxide dismutase concentrations, decreasing malondialdehyde release in skeletal muscle and increasing phosphoenolpyruvate carboxykinase mRNA expression (73). GS-Rg3 can also relieve the pain and discomfort associated with cancer and anti-cancer drugs, improving patient comfort (74,75). GS-Rg3 has also been found to stimulate sirtuin 1, which protects skeletal muscles from damage caused by reactive oxygen species and thus acts as an anti-fatigue agent (73). In rats, fatigue can decrease the production and phosphorylation of tyrosine hydroxylase, which results in a decrease in dopamine. GS-Rg3 has been shown to effectively reverse this by increasing the phosphorylation of synuclein, protein kinase A, ERK1/2 and Akt (76). These findings suggest that GS-Rg3 has potential as a natural anti-fatigue agent and may have beneficial effects in improving physical strength and relieving the pain and discomfort associated with cancer.

GS-Rg3 has emerged as a promising new anticancer agent with multifaceted and heterogeneous anticancer properties across various cancer types. Notably, GS-Rg3 has demonstrated therapeutic benefits in the treatment of liver, lung, gastric, breast, ovarian and prostate cancer. Recent literature reports have shed light on the diverse cancer-fighting mechanisms of GS-Rg3, including induction of tumor apoptosis, inhibition of tumor metastasis, proliferation and angiogenesis, enhancement of immune function, reversal of inhibitory TMEs and promotion of mitochondrial autophagy (Fig. 2). The use of immune checkpoint inhibitors has resulted in significant improvements in the treatment paradigm for various solid tumors, leading to notable enhancements in overall efficacy and patient prognosis (77). Nevertheless, the issue of resistance to immune therapy remains a significant challenge. Tumor cells exploit their inhibitory immune microenvironments to evade the effects of immune checkpoint inhibitors, a phenomenon that has been demonstrated by numerous studies to be reversible through the use of GS-Rg3. Ginseng, an ancient and valuable Chinese herbal medicine, has a notable impact on the immune system. The gut microbiota maintains a symbiotic relationship with the intestinal mucosa, which is the largest immune organ in the human body (78). Through the integration of environmental factors such as diet, with genetic and immune signals, the gut microbiota can influence the metabolism, immune function, neurodevelopment and pathogen colonization of the host. Similarly, alterations in the host immune environment can also impact the gut microbiota through different immune cells such as dendritic cells, regulatory T cells, monocytes, etc (79,80) Dysbiosis of the gut microbiota can result in changes in intestinal permeability, disrupting the existing equilibrium and affecting the metabolism and immune function of the host, thereby contributing to the development of various diseases, such as inflammatory bowel disease, depression, and cancer (80,81). In recent years, there has been increasing recognition of the importance of the gut microbiota in the diagnosis and treatment of diseases. As such, investigating whether the interaction between orally administered GS-Rg3 and the gut microbiota affects the anticancer effects of GS-Rg3 is a worthwhile endeavor.

Mitochondria, which serve as cellular energy factories, play a crucial role in cells, particularly cancer cells. Mitochondrial autophagy may exert a bidirectional regulatory effect on the occurrence and development of cancer; it can promote cancer progression by enabling cancer cells to survive under stress or it can induce carcinogenesis by affecting cell signaling transduction or promoting intracellular toxicity when mutations or abnormalities occur (82). Recent studies have also demonstrated that abnormal mitochondrial function is linked to the cellular immune response (83,84). At present, there are limited investigations regarding whether GS-Rg3 can influence cancer cell proliferation by modulating mitochondrial autophagy or other mitochondrial functions and activities. This area may be a future research focus to identify new properties that GS-Rg3 may offer in the field of antitumor therapy.

However, the low oral bioavailability of GS-Rg3, given its extensive pro-systemic metabolism and poor membrane permeability, prevents the attainment of high working concentrations in vivo (38). Given that reaching the concentration of GS-Rg3 required to inhibit cancer cell growth in vivo is challenging, efforts should also be focused on investigating new methods to improve the solubility of GS-Rg3 without decreasing the efficacy of the drug, such as in the development of cofactors to aid in solubilization. The combination of GS-Rg3 with cholesterol transport liposomes as an alternative approach has shown greater therapeutic efficacy, reduced toxicity and the potential for overcoming drug resistance, exhibiting certain synergistic effects with anticancer drugs (60). Additionally, GS-Rg3 has displayed functions that are independent of its anticancer effects, such as enhancing biocompatibility and pharmacokinetics, which offer new directions for its optimal utilization.

Overall, research in basic medicine has highlighted the marked anticancer properties of GS-Rg3 across various tumor types. However, its clinical use is predominantly restricted to primary lung cancer and liver cancer chemotherapy. The ongoing research efforts aim to fully harness the anticancer capabilities of GS-Rg3 within biological systems, potentially broadening its clinical applications to a wider range of cancer types. Meanwhile, more clinical trials should be conducted to comprehensively evaluate its safety and feasibility to realize its clinical application and benefits to patients. In summary, the evidence presented thus far suggests that GS-Rg3 is a promising anticancer agent that warrants further investigation. Further clinical trials are required to assess the effectiveness and safety of GS-Rg3 and optimize its potential for clinical implementation in cancer treatment.