Functional proteomic analysis reveals that fungal immunomodulatory protein reduced expressions of heat shock proteins correlates to apoptosis in lung cancer cells

Background: Ling Zhi-8 (LZ-8) and GMI are two fungal immunomodulatory proteins (FIPs) with a similar structure and amino acid sequence and are respectively obtained from the medicinal mushroom Ganoderma lucidum and Ganoderma microsporum. They present the anti-cancer progression and metastasis. We previously demonstrated that LZ-8 reduces the tumor progression in lung cancer LLC1 cell-bearing mouse. However, it is unclear whether these FIPs induce changes in the protein expression profile in cancer cells and the mechanism for such a process is not defined. Purpose: This study determines the changes in the proteomic profile for tumor lesions of LLC1 cell-bearing mouse received with LZ-8 and the potential mechanism for FIPs in anti-lung cancer cells. Methods: The proteomic profile of tumor lesions was determined using two-dimensional electrophoresis and a LTQ-OrbitrapXL mass spectrometer (LC-MS/MS). The biological processes and the signaling pathway enrichment analysis were performed using Ingenuity Pathway Analysis (IPA). The differentially expressed proteins were verified by Western blot. Cell viability was determined by MTT assay. Cell morphology was characterized using electron microscopy. Migration was detected using the Transwell assay. The apoptotic response was determined using Western blot and flow cytometry. Results: Obtained results showed that 21 proteins in the tumor lesions exhibited differential (2-fold change, p < 0.05) expression between PBS and LZ-8 treatment groups. LZ-8-induced changes in the proteomic profile that may relate to protein degradation pathways. Specifically, three heat shock proteins (HSPs), HSP60, 70 and 90, were significantly downregulated in tumor lesions of LLC1-bearing mouse received with LZ-8. Both LZ-8 and GMI reduced the protein levels for these HSPs in lung cancer cells. Functional studies showed that they inhibited cell migration but effectively induced apoptotic response in LLC1 cells in vitro. In addition, the inhibitors of HSP60 and HSP70 effectively inhibited cell migration and decreased cell viability of LLC1 cells. Conclusions: LZ-8 induced changes in the proteomic profile of tumor lesions which may regulate the HSPs-related cell viability. Moreover, inhibition of HSPs may be related to the anti-lung cancer activity.

Automated summary

The study demonstrates that FIPs LZ-8 and GMI induce changes in the proteomic profile of tumor lesions in LLC1 cell-bearing mouse, potentially regulating heat shock proteins (HSPs)-related cell viability and inhibiting cell migration and inducing apoptosis. Inhibition of HSPs may contribute to the anti-lung cancer activity of FIPs.