Fig 2: Comparisons of CD9 trogocytosis from non-HGSC cells and NK cells from other sources(A) CD9 expression levels in 11 HGSC and 15 non-HGSC tumor cell lines (STAR Methods).(B) Cell lines ranked by level of CD9 expression. Cell lines selected for coculture with NK-92 cells: HGSC (magenta) and non-HGSC with high levels of CD9 (green) and with lower levels of CD9 (yellow).(C) Representative flow plots showing frequency of CD9+ NK-92 cells after coculture with non-HGSC tumor cell lines.(D) Cytochalasin D partially inhibits CD9 trogocytosis from non-HGSC tumor cell lines.(E) CD9 trogocytosis by the NKL cell line and primary NK cells in peripheral blood mononuclear cells (PBMCs).

Fig 3: Kinetics of CD9 uptake by NK-92 cells from OVCAR4 cells analyzed by fluorescence cytometryOne hallmark of trogocytosis is the rapid protein uptake by a recipient cell within minutes of cell – cell contact. In this example CD9 uptake was observed at 15 min and steadily increased over this 6 h time course.

Fig 4: Cytochalasin D inhibition of CD9 uptake by NK-92 cellsCD9 uptake was significantly reduced in the presence of cytochalasin D during coculture (effector : target ratio 1 : 1, 3 h, 37°C) as measured by fluorescence-based flow cytometry (n = 3). Student’s two-tailed t test, ∗p ≤ 0.05, ∗∗p ≤ 0.01, ∗∗∗p ≤ 0.001, ∗∗∗∗p ≤ 0.0001.

Fig 5: CD9 uptake by NK-92 cells measured by CyTOF(A) 2D flow plots show increased frequency of CD9+ NK-92 cells after coculture with HGSC cell lines. When cocultured across a membrane barrier (transwells), frequencies of NK-92 cells expressing CD9 were reduced to background levels found for NK-92 cells grown in monoculture (lower row).(B) Mean and standard deviations for CD9+ NK-92 cells after coculture in the absence and presence of a membrane barrier (transwell insert) (n = 4). Student’s two-tailed t test, ∗p ≤ 0.05, ∗∗p ≤ 0.01, ∗∗∗p ≤ 0.001, ∗∗∗∗p ≤ 0.0001.