Fig. 3: ZIP1⁺ fibroblasts absorb and transfer Zn²⁺ to cancer cells through gap junctions.

a Zn²⁺ in tumour interstitial fluid (TIF) from mice with PBS (n = 4) and doxorubicin (DOX, n = 5) treatments. Mean ± SEM, Two-tailed t-test. b Necrosis in tumours with DOX treatment. N necrosis. Scale bar, 200 µm. A representative result from five independent experiments is shown. c Zn²⁺ released from dying tumour cells. LLC cells (1 × 10⁷) in 50 μL culture medium were treated at 0 °C,120 min, 95 °C, 15 min, or −80 °C, 60 min (freeze). nd, not detectable. Mean ± SEM, n = 4. Two-tailed t-test. d Relative Zn²⁺ levels in supernatants of PTX-treated LLC cells. Mean ± SD, n = 4 for DMEM and Ctl groups. n = 6 for PTX groups. Two-tailed t-test. e Zn²⁺ absorption by mCAF from the supernatant of PTX treated LLC cells. n = 3. f Zn²⁺ absorption by mCAF from extracellular space containing ZnCl₂ at indicated concentrations. n = 3. g Zn²⁺ uptake by Zip1^+/+, Zip1^+/− and Zip1^−/− MEFs. ZnCl₂, 30 μM. n = 3. h Zn²⁺ uptake by hCAF-mock or hCAF-ZIP1. n = 3. i Labile Zn²⁺ in hCAFs and A549 tumour cells (CM-Dil-labelled) co-cultured in DMEM + 10% FBS for 3 h. FluoZin3 was used to detect labile Zn²⁺ in cells. Ctl, no FluoZin3 staining. Mean ±  SEM, n = 5. Two-tailed t-test. j Labile Zn²⁺ in A549 tumour cells (preloaded with FluoZin3-AM) co-cultured with hCAFs under indicated conditions for 2 h in DMEM. TPEN: 50 μM, pre-treating hCAFs for 5 min. HEPT: heptanol, 2 mM. FluoZin3 fluorescence was read in HBSS. Mean ± SEM, n = 4. Two-tailed t-test. k Labile Zn²⁺ in A549 tumour cells (preloaded with FluoZin3-AM) co-cultured with hCAF-mock or hCAF-ZIP1 in HBSS. HEPT: 2 mM. n = 3. l Labile Zn²⁺ in LLC tumour cells (preloaded with FluoZin3-AM) co-cultured with Zip1^+/+, Zip1^+/− or Zip1^−/− MEFs in HBSS. n = 3. Two-way ANOVA test for curve comparison. Source data are provided as a Source Data file (a, c–l).