Quantitative analyses of structure-function heterogeneity of individual mitochondrial components reveal an early role of small-mitochondrial-networks in priming neoplastic transformation

Quantitative understanding of mitochondrial heterogeneity is necessary for elucidating the precise role of these multifaceted organelles in tumor cell development. We demonstrate an early mechanistic role of mitochondria in initiating neoplasticity by performing quantitative analyses of structure-function of single mitochondrial components coupled with single cell transcriptomics. We demonstrate that the large Hyperfused-Mitochondrial-Networks (HMNs) of keratinocytes promptly get converted to the heterogenous Small-Mitochondrial-Networks (SMNs) as the stem cell enriching dose of the model carcinogen, TCDD, depolarizes mitochondria. This happens by physical reorganization of the HMN nodes and edges, which enriches redox tuned SMNs with distinct network complexity. This leads to establishment of transcriptomic interaction between the upregulated redox relevant mtDNA genes and the lineage specific stemness gene, KRT15, prior to cell cycle exit. The SMN enrichment and related transcriptomic connections are sustained in the neoplastic cell population. Consistently, carcinogenic dose incapable of causing pronounced neoplastic stem cell enrichment fails to establish specific enrichment of SMNs and its linked mtDNA-KRT15(stemness) transcriptomic interaction prior to cell cycle exit. The mtDNA-KRT15 modulation is confirmed in cSCC tumors, while highlighting patient heterogeneity. Therefore, we propose that early enrichment of redox-tuned SMNs primes neoplastic transformation by establishing mtDNA-stemness transcriptomic interaction prior to cell cycle exit towards specifying quiescent neoplastic stem cells. Our data implies that redox-tuned SMNs, created by mitochondrial fission, would be sustained by tuning the balance of mitochondrial fission-fusion during neoplastic transformation. The proposed early role of mitochondria in cancer etiology is potentially relevant for designing precision strategies for cancer prevention and therapy. Significance StatementThe challenges of understanding the complex role of the multifaceted and heterogenous cellular organelles, mitochondria, can be potentially overcome with their quantitative analyses. We use a combinatorial approach of quantitative analyses of single-mitochondrial-components and scRNA-seq to elucidate a mechanism of mitochondrial priming of cancer initiation by a model carcinogen. We propose that conversion of large Hyperfused-Mitochondrial-Networks (HMNs) to Small-Mitochondrial-Networks (SMNs) primes non-transformed keratinocytes towards their neoplastic transformation. Mechanistically, the SMNs, enriched by modulation of the physical nodes and edges of mitochondrial networks, tunes mitochondrial redox balance to establish transcriptomic interactions towards specifying a state of stemness. Further probing of our fundamental findings in the light of cancer heterogeneity may facilitate refinement of the various proposed mitochondria based targeted cancer therapies.