Characterization of 11 human sarcoma cell strains: evaluation of cytogenetics, tumorigenicity, metastasis, and production of angiogenic factors

Three-Dimensional Patient-Derived In Vitro Sarcoma Models: Promising Tools for Improving Clinical Tumor Management

Over the past decade, the development of new targeted therapeutics directed against specific molecular pathways involved in tumor cell proliferation and survival has allowed an essential improvement in carcinoma treatment. Unfortunately, the scenario is different for sarcomas, a group of malignant neoplasms originating from mesenchymal cells, for which the main therapeutic approach still consists in the combination of surgery, chemotherapy, and radiation therapy. The lack of innovative approaches in sarcoma treatment stems from the high degree of heterogeneity of this tumor type, with more that 70 different histopathological subtypes, and the limited knowledge of the molecular drivers of tumor development and progression. Currently, molecular therapies are available mainly for the treatment of gastrointestinal stromal tumor, a soft-tissue malignancy characterized by an activating mutation of the tyrosine kinase KIT. Since the first application of this approach, a strong effort has been made to understand sarcoma molecular alterations that can be potential targets for therapy. The low incidence combined with the high level of histopathological heterogeneity makes the development of clinical trials for sarcomas very challenging. For this reason, preclinical studies are needed to better understand tumor biology with the aim to develop new targeted therapeutics. Currently, these studies are mainly based on in vitro testing, since cell lines, and in particular patient-derived models, represent a reliable and easy to handle tool for investigation. In the present review, we summarize the most important models currently available in the field, focusing in particular on the three-dimensional spheroid/organoid model. This innovative approach for studying tumor biology better represents tissue architecture and cell–cell as well as cell–microenvironment crosstalk, which are fundamental steps for tumor cell proliferation and survival.

Targeted therapies for soft-tissue sarcomas

The past several decades have revealed certain challenges that are inherent to soft-tissue sarcomas with regards to devising, testing and setting treatment paradigms for such a rare and heterogeneous malignancy. Despite this, significant advances have been made through the efforts of scientists, clinicians and patients alike. We are now entering a molecular era of cancer and current biotechnology is beginning to unravel the pathogenic enigma of these often devastating tumors. As our understanding of these malignancies improves, so does our list of potential treatment options. The impetus now lies with the medical/scientific community to direct translational research and subsequently the development and clinical testing of novel compounds in a fashion that best serves this unique patient population. To do so, we must continue to integrate the lessons of the past with the resources and promise of the future. This review will outline current areas of therapeutic interest in soft-tissue sarcomas with regard to agents that have reached clinical testing.

Fibroblast growth factor 2 orchestrates angiogenic networking in non-GIST STS patients

Background

Non-gastrointestinal stromal tumor soft-tissue sarcomas (non-GIST STSs) constitute a heterogeneous group of tumors with poor prognosis. Fibroblast growth factor 2 (FGF2) and fibroblast growth factor receptor-1 (FGFR-1), in close interplay with platelet-derived growth factor-B (PDGF-B) and vascular endothelial growth factor receptor-3 (VEGFR-3), are strongly involved in angiogenesis. This study investigates the prognostic impact of FGF2 and FGFR-1 and explores the impact of their co-expression with PDGF-B and VEGFR-3 in widely resected tumors from non-GIST STS patients.

Methods

Tumor samples from 108 non-GIST STS patients were obtained and tissue microarrays were constructed for each specimen. Immunohistochemistry was used to evaluate the expressions of FGF-2, FGFR-1, PDGF-B and VEGFR-3.

Results

In the multivariate analysis, high expression of FGF2 (P = 0.024, HR = 2.2, 95% CI 1.1-4.4) and the co-expressions of FGF2 & PDGF-B (overall; P = 0.007, intermediate; P = 0.013, HR = 3.6, 95% CI = 1.3-9.7, high; P = 0.002, HR = 6.0, 95% CI = 2.0-18.1) and FGF2 & VEGFR-3 (overall; P = 0.050, intermediate; P = 0.058, HR = 2.0, 95% CI = 0.98-4.1, high; P = 0.028, HR = 2.6, 95% CI = 1.1-6.0) were significant independent prognostic indicators of poor disease-specific survival.

Conclusion

FGF2, alone or in co-expression with PDGF-B and VEGFR-3, is a significant independent negative prognosticator in widely resected non-GIST STS patients.

Benign mesenchymal stromal cells in human sarcomas

PURPOSE

Recent evidence suggests that at least some sarcomas arise through aberrant differentiation of mesenchymal stromal cells (MSCs), but MSCs have never been isolated directly from human sarcoma specimens.

EXPERIMENTAL DESIGN

We examined human sarcoma cell lines and primary adherent cultures derived from human sarcoma surgical samples for features of MSCs. We further characterized primary cultures as either benign or malignant by the presence of tumor-defining genetic lesions and tumor formation in immunocompromised mice.

RESULTS

We show that a dedifferentiated liposarcoma cell line DDLS8817 posesses fat, bone, and cartilage trilineage differentiation potential characteristic of MSCs. Primary sarcoma cultures have the morphology, surface immunophenotype, and differentiation potential characteristic of MSCs. Surprisingly, many of these cultures are benign, as they do not form tumors in mice and lack sarcoma-defining genetic lesions. Consistent with the recently proposed pericyte origin of MSCs in normal human tissues, sarcoma-derived benign MSCs (SDBMSCs) express markers of pericytes and cooperate with endothelial cells in tube formation assays. In human sarcoma specimens, a subset of CD146-positive microvascular pericytes expresses CD105, an MSC marker, whereas malignant cells largely do not. In an in vitro coculture model, SDBMSCs as well as normal human pericytes markedly stimulate the growth of sarcoma cell lines.

CONCLUSIONS

SDBMSCs/pericytes represent a previously undescribed stromal cell type in sarcoma that may contribute to tumor formation.

Comments on cultured human sarcoma cells

Human sarcoma cell populations maintained in culture reflect to the native tumor cells better if the culture retains those nonmalignant cells that comprised the tumor's microenvironment in vivo [Hu M, et al. Characterization of 11 human sarcoma cell strains. Cancer 2002; 95: 1569–76] and thus provide paracrine growth factors and protection from apoptotic death to the tumor cells. Whereas sarcoma cell cultures obtained through meticulous efforts aimed at the elimination of all non-malignant cells of the tumor's original microenvironment consist of subpopulations of tumor cells growing exclusively with the support of their own autocrine growth loops [Sinkovics JG, et al. Growth of human tumor cells in established cultures. In: Busch H, ed. Methods in Cancer Research. Vol 14. New York: Academic Press, 1978; 243–323].

Isolated limb perfusion: a novel delivery system for wild-type p53 and fiber-modified oncolytic adenoviruses to extremity sarcoma

Isolated limb perfusion (ILP) is a limb salvage surgical modality used to deliver chemotherapy and biologic agents to locally advanced and recurrent extremity soft tissue sarcoma (STS), and may be readily tailored for delivery of gene therapy. We set out to test the feasibility of delivering AdFLAGp53 (replication incompetent adenovirus bearing FLAG-tagged wild-type p53) and Ad.hTC.GFP/E1a.RGD (a fiber-modified, replication selective oncolytic adenovirus) into human leiomyosarcoma xenografts by ILP. Nude rats bearing SKLMS-1 tumors in their hind limbs underwent ILP with escalating doses of AdLacZ or AdFLAGp53 (study 1), or with Ad.CMV.GFP.RGD or Ad.hTC.GFP/E1a.RGD (study 2) following in vitro confirmation of therapeutic potential in STS cell lines and strains. Seventy-two hours after delivery, reverse transcription-polymerase chain reaction confirmed FLAGp53 expression, and immunohistochemistry confirmed diffuse upregulation of p21CIP1/WAF1 in ILP-treated tumors. Ad.hTC.GFP/E1a.RGD perfused tumors demonstrated robust macroscopic transgene expression throughout their substance, but not in perfused normal tissues, 21 days after delivery. Intra-tumoral viral replication was confirmed by immunohistochemical staining for early (E1a) and late (hexon) viral protein expression. Terminal deoxynucleotidyl transferase-mediated-digoxigenin nick end-labeling staining identified foci of cell death within regions of viral replication. In conclusion, therapeutic adenoviral gene therapy against limb borne human STS can be successfully delivered by ILP and warrants further investigation.

Effect of basic fibroblast growth factor on growth regulation in Bel-7402 cell line

AIM

To investigate whether bFGF regulates p21^WAF1 expression of Bel-7402 cell line via PI3K/PKB pathway.

METHODS

32P incorporation assay. The expression of p21^WAF1-mRNA was assessed by RT-PCR. The expression of p21^WAF1 protein was detected by Western blot. Cell cycle analysis was performed on a FACScan.

RESULTS

Both membrane and cytosol activity of PKB in Bel-7402 cell which were treated with bFGF (25 mg/L) reached the peak at 10 min. p21^WAF1 mRNA level was upregulated and peaked at 1 h (5.5 fold induction). Correspondingly, p21^WAF1 expression was increased and peaked at 2 h (2.2 folds of reduction). Wortmannin efficiently inhibited the activity of PKB (P <0.05), but not the level of p21^WAF1 mRNA and the expression of p21^WAF1 protein. FCM analysis showed bFGF induced S-phase entry (0.14±0.01→0.28±0.01, P <0.01), which was inhibited by wortmannin effectively (0.28±0.01→0.22±0.01, P <0.01).

CONCLUSION

bFGF stimulates the proliferation of Bel-7402 cell line via PI3K/PKB pathway, and modulates p21^WAF1 expression through separating signaling pathways.