Polyploid giant cancer cells (PGCCs) have been observed by pathologists for over a century. PGCCs contribute to solid tumor heterogeneity, but their functions are largely undefined. Little attention has been given to these cells, largely because PGCCs have been generally thought to originate from repeated mitosis/cytokinesis failure and have no capacity for long-term survival and cell proliferation. Here we report that we successfully purified and cultured PGCCs from human ovarian cancer cell lines and primary ovarian cancer. These cells are highly resistant to oxygen deprivation and could form through endoreduplication or cell fusion, generating regular-sized cancer cells quickly through budding or burst. They are positive for normal and cancer stem cell markers, divided asymmetrically and cycled slowly. They can differentiate into adipose, cartilage, and bone. A single PGCC formed cancer spheroids in vitro and generated tumors in immunodeficient mice. PGCC-derived tumor gained a mesenchymal phenotype with increased expression of cancer stem cell markers CD44 and CD133 and become more resistant to the treatment of cisplatin. Together, our results reveal that the PGCCs present a resistant form of human cancer generated in response to hypoxia stress and can contribute to generation of cancer stem-like cells and play a fundamental role in regulating tumor heterogeneity, stemness, and chemoresistance in human cancer.

Reactive stromal cells are an integral part of tumor microenvironment (TME) and interact with cancer cells to regulate their growth. Although targeting stromal cells could be a viable therapy to regulate the communication between TME and cancer cells, identification of stromal targets that make cancer cells vulnerable has remained challenging and elusive. Here, we identify a previously unrecognized mechanism whereby metabolism of reactive stromal cells is reprogrammed through an upregulated glutamine anabolic pathway. This dysfunctional stromal metabolism confers atypical metabolic flexibility and adaptive mechanisms in stromal cells, allowing them to harness carbon and nitrogen from noncanonical sources to synthesize glutamine in nutrient-deprived conditions existing in TME. Using an orthotopic mouse model for ovarian carcinoma, we find that co-targeting glutamine synthetase in stroma and glutaminase in cancer cells reduces tumor weight, nodules, and metastasis. We present a synthetic lethal approach to target tumor stroma and cancer cells simultaneously for desirable therapeutic outcomes.

Glutamine can play a critical role in cellular growth in multiple cancers. Glutamine‐addicted cancer cells are dependent on glutamine for viability, and their metabolism is reprogrammed for glutamine utilization through the tricarboxylic acid (TCA) cycle. Here, we have uncovered a missing link between cancer invasiveness and glutamine dependence. Using isotope tracer and bioenergetic analysis, we found that low‐invasive ovarian cancer (OVCA) cells are glutamine independent, whereas high‐invasive OVCA cells are markedly glutamine dependent. Consistent with our findings, OVCA patients’ microarray data suggest that glutaminolysis correlates with poor survival. Notably, the ratio of gene expression associated with glutamine anabolism versus catabolism has emerged as a novel biomarker for patient prognosis. Significantly, we found that glutamine regulates the activation of STAT3, a mediator of signaling pathways which regulates cancer hallmarks in invasive OVCA cells. Our findings suggest that a combined approach of targeting high‐invasive OVCA cells by blocking glutamine's entry into the TCA cycle, along with targeting low‐invasive OVCA cells by inhibiting glutamine synthesis and STAT3 may lead to potential therapeutic approaches for treating OVCAs.

Epithelial-stromal interactions play a critical role in tumor initiation and progression; cancer-associated stroma, but not normal stroma, is known to be tumor-promoting. However, the molecular signal used by epithelial cancer cells to reprogram normal stroma to a tumorigenic stroma is not known. Here, we present evidence to suggest that the chemokine growth-regulated oncogene 1 (Gro-1) may be one such signaling molecule. We showed that the expression of Gro-1 is activated by RAS and is vital for cell survival and the malignant transformation of ovarian epithelial cells. Surprisingly, we found that Gro-1 is a potent inducer of senescence in stromal fibroblasts and that this effect depends on functional p53. Senescent fibroblasts induced by Gro-1 can promote tumor growth whereas abrogation of senescence through immortalization results in loss of such tumor promoting activity. We also demonstrated that stromal fibroblasts adjacent to epithelial cancer cells are senescent in human ovarian cancer specimens and in heterografts from RAS-transformed human ovarian epithelial cells and ovarian cancer cells. Moreover, Gro-1 was expressed at significantly higher amounts in ovarian cancer than in normal tissues and was higher in serum samples from women with ovarian cancer than in serum from women without ovarian cancer. These findings provide strong evidence that RAS-induced Gro-1 can reprogram the stromal microenvironment through the induction of senescence of fibroblasts and thus can promote tumorigenesis. Therefore, Gro-1 may be a therapeutic target as well as a diagnostic marker in ovarian cancer.ovarian cancer ͉ Ras ͉ transformation ͉ tumor microenvironment

Our recent perplexing findings that polyploid giant cancer cells (PGCCs) acquired embryonic-like stemness and were capable of tumor initiation raised two important unanswered questions: how do PGCCs acquire such stemness, and to which stage of normal development do PGCCs correspond. Intriguingly, formation of giant cells due to failed mitosis/cytokinesis is common in the blastomere stage of the preimplantation embryo. However, the relationship between PGCCs and giant blastomeres has never been studied. Here, we tracked the fate of single PGCCs following paclitaxel-induced mitotic failure. Morphologically, early spheroids derived from PGCCs were indistinguishable from human embryos at the blastomere, polyploid blastomere, compaction, morula and blastocyst-like stages by light, scanning electron or three-dimensional confocal scanning microscopy. Formation of PGCCs was associated with activation of senescence, while budding of daughter cells was associated with senescence escape. PGCCs showed time- and space-dependent activation of expression of the embryonic stem cell markers OCT4, NANOG, SOX2 and SSEA1 and lacked expression of Xist. PGCCs acquired mesenchymal phenotype and were capable of differentiation into all three germ layers in vitro. The embryonic-like stemness of PGCCs was associated with nuclear accumulation of YAP, a key mediator of the Hippo pathway. Spheroids derived from single PGCCs grew into a wide spectrum of human neoplasms, including germ cell tumors, high-grade and low-grade carcinomas and benign tissues. Daughter cells derived from PGCCs showed attenuated capacity for invasion and increased resistance to paclitaxel. We also observed formation of PGCCs and dedifferentiation in ovarian cancer specimens from patients treated with chemotherapy. Taken together, our findings demonstrate that PGCCs represent somatic equivalents of blastomeres, the most primitive cancer stem cells reported to date. Thus, our studies reveal an evolutionarily conserved archaic embryonic program in somatic cells that can be de-repressed for oncogenesis. Our work offers a new paradigm for cancer origin and disease relapse.