Cell fusion in vitro has been used to study cancer, gene mapping and regulation, and the production of antibodies via hybridomas. However, in-vivo heterosynkaryon formation by cell-cell fusion has received less attention. This investigation describes the spontaneous fusion of a human glioblastoma with normal hamster cells after xenogeneic transplantation, resulting in malignant cells that express both human and hamster genes and gene products, and retention of glioblastoma traits with an enhanced ability to metastasize. Three of 7 human genes found showed translation of their proteins during serial propagation in vivo or in vitro for years; namely, CD74, CXCR4, and PLAGL2, each implicated with malignancy or glioblastoma. This supports the thesis that genetic hybridization of cancer and normal cells can transmit malignancy and also, as first described herein, regulatory genes involved in the tumor’s organotypic morphology. Evidence also is increasing that even cell-free human cancer DNA can induce malignancy and transfer genetic information to normal cells. Hence, we posit that the transfer of genetic information between tumor and stromal cells, whether by cell-cell fusion or other mechanisms, is implicated in the progression of malignancy, and may further define the crosstalk between cancer cells and their stromal neighbors.

Ranpirnase (Rap), an amphibian RNase, has been extensively studied both preclinically and clinically as an antitumor agent. Rap can be administered repeatedly to patients without any untoward immune response, with reversible renal toxicity reported to be dose limiting. To enhance its potency and targeted tumor therapy, we describe the generation of a novel IgG-based immunotoxin, designated 2L-Rap(Q)-hRS7, comprising Rap (Q), a mutant Rap with the putative N-glycosylation site removed, and hRS7, an internalizing, humanized antibody against Trop-2, a cell surface glycoprotein overexpressed in variety of epithelial cancers. The immunotoxin was generated recombinantly by fusing Rap(Q) to each of the two hRS7 light (L) chains at the NH 2 terminus, produced in stably transfected myeloma cells, purified by Protein A, and evaluated by a panel of in vitro studies. The results, including size-exclusion high-performance liquid chromatography, SDS-PAGE, flow cytometry, RNase activity, internalization, cell viability, and colony formation, showed its purity, molecular integrity, comparable affinity to hRS7 for binding to several Trop-2-expressing cell lines of different cancer types, and potency to inhibit growth of these cell lines at nanomolar concentrations. In addition, 2L-Rap (Q)-hRS7 suppressed tumor growth in a prophylactic model of nude mice bearing Calu-3 human non-small cell lung cancer xenografts, with an increase in the median survival time from 55 to 96 days (P < 0.01). These results warrant further development of 2L-Rap(Q)-hRS7 as a potential therapeutic for various Trop-2-expressing cancers, such as cervical, breast, colon, pancreatic, ovarian, and prostate cancers. Mol Cancer Ther; 9(8); 2276-86. ©2010 AACR.

We report the in-vivo fusion of two Hodgkin lymphomas with golden hamster cheek pouch cells, resulting in serially-transplanted (over 5–6 years) GW-532 and GW-584 heterosynkaryon tumor cells displaying both human and hamster DNA (by FISH), lymphoma-like morphology, aggressive metastasis, and retention of 7 human genes (CD74, CXCR4, CD19, CD20, CD71, CD79b, and VIM) out of 24 tested by PCR. The prevalence of B-cell restricted genes (CD19, CD20, and CD79b) suggests that this uniform population may be the clonal initiating (malignant) cells of Hodgkin lymphoma, despite their not showing translation to their respective proteins by immunohistochemical analysis. This is believed to be the first report of in-vivo cell-cell fusion of human lymphoma and rodent host cells, and may be a method to disclose genes regulating both organoid and metastasis signatures, suggesting that the horizontal transfer of tumor DNA to adjacent stromal cells may be implicated in tumor heterogeneity and progression. The B-cell gene signature of the hybrid xenografts suggests that Hodgkin lymphoma, or its initiating cells, is a B-cell malignancy.

After demonstrating, with karyotyping, polymerase chain reaction (PCR) and fluorescence in-situ hybridization, the retention of certain human chromosomes and genes following the spontaneous fusion of human tumor and hamster cells in-vivo, it was postulated that cell fusion causes the horizontal transmission of malignancy and donor genes. Here, we analyzed gene expression profiles of 3 different hybrid tumors first generated in the hamster cheek pouch after human tumor grafting, and then propagated in hamsters and in cell cultures for years: two Hodgkin lymphomas (GW-532, GW-584) and a glioblastoma multiforme (GB-749). Based on the criteria of MAS 5.0 detection P-values ≤0.065 and at least a 2-fold greater signal expression value than a hamster melanoma control, we identified 3,759 probe sets (ranging from 1,040 to 1,303 in each transplant) from formalin-fixed, paraffin-embedded sections of the 3 hybrid tumors, which unambiguously mapped to 3,107 unique Entrez Gene IDs, representative of all human chromosomes; however, by karyology, one of the hybrid tumors (GB-749) had a total of 15 human chromosomes in its cells. Among the genes mapped, 39 probe sets, representing 33 unique Entrez Gene IDs, complied with the detection criteria in all hybrid tumor samples. Five of these 33 genes encode transcription factors that are known to regulate cell growth and differentiation; five encode cell adhesion- and transmigration-associated proteins that participate in oncogenesis and/or metastasis and invasion; and additional genes encode proteins involved in signaling pathways, regulation of apoptosis, DNA repair, and multidrug resistance. These findings were corroborated by PCR and reverse transcription PCR, showing the presence of human alphoid (α)-satellite DNA and the F11R transcripts in additional tumor transplant generations. We posit that in-vivo fusion discloses genes implicated in tumor progression, and gene families coding for the organoid phenotype. Thus, cancer cells can transduce adjacent stromal cells, with the resulting progeny having permanently transcribed genes with malignant and other gene functions of the donor DNA. Using heterospecific in-vivo cell fusion, genes encoding oncogenic and organogenic traits may be identified.