Inhibition of dormant lung cancer cell reactivation by Punica granatum peel and Dioscorea nipponica: involving myc, skp2 and p27

Introduction: Dormant cancer cells, capable of reactivating from the G₀ phase, drive tumor recurrence and therapy resistance. Current clinical strategies targeting dormancy remain limited. This study evaluates Punica granatum peel (PGP) and Dioscorea Nipponica (DN) for their ability to sustain dormancy in lung cancer cells and inhibit reactivation. 

Methods: Dormancy was induced in A549 and H460 lung cancer cells via contact inhibition or serum deprivation. Subcutaneous and orthotopic xenograft mouse models were employed. Cells and mice were treated with PGP, DN, or their combination. SYBR Green assays, flow cytometry, and immunoblotting assessed DNA synthesis, cell cycle phases, and protein expression (p27, SKP2, cMYC, AURORA A, SUPT16H, SSRP1). 

Results: Both PGP and DN significantly inhibited DNA synthesis and cell cycle re-entry (G₀-to-G₁ transition) in vitro. In vivo, tumor volume and weight decreased by 26–50% (p < 0.05) in treated mice. Treatments upregulated p27 while downregulating SKP2, cMYC, AURORA A, SUPT16H, and SSRP1. No synergistic effect was observed, but additive efficacy (Combination Index ≈1) was noted at a 10:1 PGP:DN ratio. 

Discussion: PGP and DN sustain dormancy by modulating key cell cycle regulators, highlighting their potential to reduce recurrence and combat drug resistance. These findings underscore the therapeutic promise of traditional Chinese medicines in managing dormant cancer cells. Future studies should identify active compounds and validate mechanisms in advanced models.