Tetraploidization of Immortalized Myoblasts Induced by Cell Fusion Drives Myogenic Sarcoma Development with DMD Deletion

Proteins implicated in muscular dystrophy and cancer are functional constituents of the centrosome

Aberrant expression of dystrophin, utrophin, dysferlin, or calpain-3 was originally identified in muscular dystrophies (MDs). Increasing evidence now indicates that these proteins might act as tumor suppressors in myogenic and non-myogenic cancers. As DNA damage and somatic aneuploidy, hallmarks of cancer, are early pathological signs in MDs, we hypothesized that a common pathway might involve the centrosome. Here, we show that dystrophin, utrophin, dysferlin, and calpain-3 are functional constituents of the centrosome. In myoblasts, lack of any of these proteins caused excess centrosomes, centrosome misorientation, nuclear abnormalities, and impaired microtubule nucleation. In dystrophin double-mutants, these defects were significantly aggravated. Moreover, we demonstrate that also in non-myogenic cells, all four MD-related proteins localize to the centrosome, including the muscle-specific full-length dystrophin isoform. Therefore, MD-related proteins might share a convergent function at the centrosome in addition to their diverse, well-established muscle-specific functions. Thus, our findings support the notion that cancer-like centrosome-related defects underlie MDs and establish a novel concept linking MDs to cancer.

Cell fusion enhances energy metabolism of mesenchymal tumor hybrid cells to sustain their proliferation and invasion

BACKGROUND

Cell-to-cell fusion is emerging as a key element of the metastatic process in various cancer types. We recently showed that hybrids made from the spontaneous merging of pre-malignant (IMR90 E6E7, i.e. E6E7) and malignant (IMR90 E6E7 RST, i.e. RST) mesenchymal cells recapitulate the main features of human undifferentiated pleomorphic sarcoma (UPS), with a highly rearranged genome and increased spreading capacities. To better characterize the intrinsic properties of these hybrids, we investigated here their metabolic energy profile compared to their parents.

RESULTS

Our results unveiled that hybrids harbored a Warburg-like metabolism, like their RST counterparts. However, hybrids displayed a much greater metabolic activity, enhancing glycolysis to proliferate. Interestingly, modifying the metabolic environmental conditions through the use of 5-aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR), an activator of the 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK), specifically reduced the growth of hybrids, and also abrogated the invasive capacity of hybrids displaying enhanced glycolysis. Furthermore, AICAR efficiently blocked the tumoral features related to the aggressiveness of human UPS cell lines.

CONCLUSION

Altogether, our findings strongly suggest that hybrids rely on higher energy flux to proliferate and that a drug altering this metabolic equilibrium could impair their survival and be potentially considered as a novel therapeutic strategy.

Acquisition of cancer stem cell capacities after spontaneous cell fusion

Background

Cancer stem/Initiating cell (CS/IC) hypothesis argues that CS/ICs are responsible of tumour initiation, drug resistance, metastasis or disease relapse. Their detection in several cancers supports this concept. However, their origin is still misunderstood. Cell fusion is shown to take part in the formation of CS/ICs, i.e. fusion between mesenchymal stem cell and cancer cell. In a previous paper, we described that fusion leads to hybrids with metastatic capacity. This process triggered genomic rearrangements in hybrid cells together with increased metastasis development. Here, we hypothesize that cell fusion could be strong enough to provoke a cellular reprogramming and the acquisition of CS/IC properties, promoting metastasis formation.

Methods

After spontaneous cell fusion between E6E7 (IMR90 with the oncogenes E6 and E7) and RST (IMR90 fully transformed) cell lines, hybrid cells were selected by dual antibiotic selection. Cancer stem cells capacities were evaluated regarding capacity to form spheres, expression of stem cell markers and the presence of ALDHhigh cells.

Results

Our data show that after cell fusion, all hybrids contain a percentage of cells with CS/ICs properties, regarding. Importantly, we lastly showed that NANOG inhibition in H1 hybrid decreases this migration capacity while having no effect on the corresponding parental cells.

Conclusions

Altogether these results indicate that the combination of CS/ICs properties and genomic rearrangement in hybrids is likely to be key to tumour progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07979-2.