caf scores were consistently higher in miro2 spots and neighboring regions compared to non - miro2 spots, although only minor differences were observed among the four caf subtypes ( extended data fig. 7d ). fig. 6miro2 is overexpressed at the leading edge of sccs. a, dot plot showing expression of mitochondrial trafficking genes; violin plot showing expression of miro2 in different cell types in sccs ( n = 5, 799 myeloid cells, 4, 644 tumor cells, 1, 495 epithelial cells, 584 fibroblasts, 413 lymphoid cells, 169 endothelial cells and 129 melanocyte s ). b, violin plot showing expression of miro2 in tumor cell subpopulations in sccs based on scrna - seq data ( n = 296 tumor - specific keratinocytes ( tsks ), 1, 385 basal tumor keratinocytes ( kc ), 725 cycling tumor keratinocytes and 2238 differentiating tumor keratinocytes ). c, feature plots showing spatial distribution of miro2 transcripts in human skin scc; violin blots showing miro2 transcripts at the tumor leading edge versus the total tumor and its microenvironment ( tme ) ( n = 2 tumors from different patients; p2 and p6 ). d, western blot of lysates from hpfs, hacat, hacat - ras and a431 cells for miro2 and gapdh. e, miro2 and k14 immunoflu orescence stainings of sections from 3d organotypic skin cultures with hpfs and hacat or a431 cells and quantification of the miro2 - positive area ( n = 3 3d cultures per epithelial cell line ). f, forest plot showing the 5 - year disease-specific survival ( dss ) associated with miro2 expression across solid cancers based on tcga. hazard ratios ( hrs ) and 95 % confidence intervals ( cis ) based on cox proportional hazard model are shown. the last point represents the estimate from the random - effects meta - analysis ( n = 8, 941 patients ). g, pearson correlation coefficient ( ρ ) and 95 % cis between the enrichment score of the leading edge ( le ) signature and miro2 expression across the different solid cancers in tcga. the last point represents the estimate from the random - effects meta - analysis ( n = 10, 238 patients ). h, dependency of different cancers on miro2 expression as documented in the depmap portal. gene effect scores are derived from demeter2 or ceres. a lower score denotes a greater dependency on expression. violin plots in a – c show the median ( center line ), 25th and 75th percentiles ( box bounds ) and whiskers extending to the most extreme data points within 1. 5 times the interquartile range from the box. points outside this range are plotted as outliers. the graph in e shows the mean ± s. e. m. a mann – whitney u - test for comparison between two groups ( a, b ) or unpaired two - sided student ’ s t - test ( e ) was used to determine statistical significance. source data a, dot plot showing expression of mitochondrial trafficking genes; violin plot showing expression of miro2 in different cell types in sccs ( n = 5, 799 myeloid cells, 4, 644 tumor cells, 1, 495 epithelial cells, 584 fibroblasts, 413 lymphoid cells, 169 endothelial cells and 129 melanocyte s ). b, violin plot showing expression of miro2 in tumor cell subpopulations in sccs based on scrna - seq data ( n = 296 tumor - specific keratinocytes ( tsks ), 1, 385 basal tumor keratinocytes ( kc ), 725 cycling tumor keratinocytes and 2238 differentiating tumor keratinocytes ). c, feature plots showing spatial distribution of miro2 transcripts in human skin scc; violin blots showing miro2 transcripts at the tumor leading edge versus the total tumor and its microenvironment ( tme ) ( n = 2 tumors from different patients; p2 and p6 ). d, western blot of lysates from hpfs, hacat, hacat - ras and a431 cells for miro2 and gapdh. e, miro2 and k14 immunoflu orescence stainings of sections from 3d organotypic skin cultures with hpfs and hacat or a431 cells and quantification of the miro2 - positive area ( n = 3 3d cultures per epithelial cell line ). f, forest plot showing the 5 - year disease-specific survival ( dss ) associated with miro2 expression across solid cancers based on tcga. hazard ratios ( hrs ) and 95 % confidence intervals ( cis ) based on cox proportional hazard model are shown. the last point represents the estimate from the random - effects meta - analysis ( n = 8, 941 patients ). g, pearson correlation coefficient ( ρ ) and 95 % cis between the enrichment score of the leading edge ( le ) signature and miro2 expression across the different solid cancers in tcga. the last point represents the estimate from the random - effects meta - analysis ( n = 10, 238 patients ). h, dependency of different cancers on miro2 expression as documented in the depmap portal. gene effect scores are derived from demeter2 or ceres. a lower score denotes a greater dependency on expression. violin plots in a – c show the median ( center line ), 25th and 75th percentiles ( box bounds ) and whiskers extending to the most extreme data points within 1. 5 times the interquartile range from the box. points outside this range are plotted as outliers. the graph in e shows the mean ± s. e. m. a mann – whitney u - test for comparison between two groups ( a, b ) or unpaired two - sided student ’ s t - test ( e ) was used to determine statistical significance. source data western blot analysis showed strong expression of miro2 in a431 and hacat - ras cells but it was hardly detectable in the parental hacat cells and in fibroblasts ( fig. 6d ). the predominant expression of miro2 in the epithelium was confirmed by immunostaining of three - dimensional ( 3d ) organotypic cultures ( fig. 6e ). increased miro2 expression did not consistently correlate with poor survival across 30 different tumors ( fig. 6f and extended data fig. 8 ). however, the cancer expression data are based on bulk cancer tissue, whereas the expression of miro2 was mainly upregulated at the tumor edge. indeed, analysis of the leading edge signature from oral scc showed a positive correlation of this signature with miro2 expression across most of the 30 cancer types ( fig. 6g ). this is of likely functional relevance, because cancer dependency map ( depmap ) analysis showed an important role of miro2 in the proliferation and survival of cancer cells ( fig. 6h ). we next investigated the impact of miro2 knockdown on intercellular mitochondrial transfer by establishing cocultures of hpfs and lifeact a431 cells, which were transfected with miro2 or scrambled sirnas and stained with mitotracker green ( fig. 7a, b ). transfection with fluorescently labeled sirna showed no detectable transfer of sirna to cocultured hpfs ( extended data fig. 9a ). consistently, hpfs isolated from cocultures of a431 cells transfected with simiro2 or sictrl showed no significant difference in miro2 expression ( extended data fig. 9b ). fig. 7miro2 is required for mitochondrial transfer. a, rt – qpcr for miro2 using rna from sictrl or simiro2 a431 cells; western blot of total and mitochondrial lysates from these cells for miro2, vinculin or hsp60 ( loading controls ) ( n = 3 cultures per group ). b, fluorescence images of lifeact a431 cells ( red ) stained with mitotracker green and transfected with sictrl or simiro2 in coculture with hpfs, counterstained with hoechst. white arrowheads indicate a431 cells. c, percentage of mitotracker - high hpfs in cocultures with simiro2 or sictrl a431 cells, normalized to the number of cancer cells ( n = 3 cocultures per group ). d, qpcr for mtdna encoding trna - leu ( uur ) relative to nucdna encoding b2m using dna from a431 cells transfected with sictrl or simiro2. total mtdna content was calculated on the basis of ct values ( n = 3 cultures per group ). e, mitochondrial mass in sictrl and simiro2 a431 cells based on mitotracker green mean fluorescence intensity ( mfi ) ( n = 3 per group ). f, confocal images of sictrl or simiro2 a431 cells incubated with mitotracker green. the dashed line marks the outer edge of the cell ( n = 3 cultures per group ).