Gene therapy of melanoma pulmonary metastasis by intramuscular injection of plasmid DNA encoding tissue inhibitor of metalloproteinases-1

The Establishment of a Lung Colonization Assay for Circulating Tumor Cell Visualization in Lung Tissues

Metastasis is the major cause of cancer death. The role of circulating tumor cells (CTCs) in promoting cancer metastasis, in which lung colonization by CTCs critically contributes to early lung metastatic processes, has been vigorously investigated. As such, animal models are the only approach that captures the full systemic process of metastasis. Given that problems occur in previous experimental designs for examining the contributions of CTCs to blood vessel extravasation, we established an in vivo lung colonization assay in which a long-term-fluorescence cell-tracer, carboxyfluorescein succinimidyl ester (CFSE), was used to label suspended tumor cells and lung perfusion was performed to clear non-specifically trapped CTCs prior to lung removal, confocal imaging, and quantification. Polymeric fibronectin (polyFN) assembled on CTC surfaces has been found to mediate lung colonization in the final establishment of metastatic tumor tissues. Here, to specifically test the requirement of polyFN assembly on CTCs for lung colonization and extravasation, we performed short term lung colonization assays in which suspended Lewis lung carcinoma cells (LLCs) stably expressing FN-shRNA (shFN) or scramble-shRNA (shScr) and pre-labeled with 20 μM of CFSE were intravenously inoculated into C57BL/6 mice. We successfully demonstrated that the abilities of shFN LLC cells to colonize the mouse lungs were significantly diminished in comparison to shScr LLC cells. Therefore, this short-term methodology may be widely applied to specifically demonstrate the ability of CTCs within the circulation to colonize the lungs.

IL-12 immunotherapy of Braf(V600E)-induced papillary thyroid cancer in a mouse model

Papillary thyroid carcinoma (PTC) accounts for >80% thyroid malignancies, and BRAF(V600E) mutation is frequently found in >40% PTC. Interleukin-12 (IL-12) is a proinflammatory heterodimeric cytokine with strong antitumor activity. It is not known whether IL-12 immunotherapy is effective against Braf(V600E)-induced PTC. In the present study, we investigated the effectiveness of IL-12 immunotherapy against Braf(V600E)-induced PTC in LSL-Braf(V600E)/TPO-Cre mice. LSL-Braf(V600E)/TPO-Cre mice were created for thyroid-specific expression of Braf(V600E) under the endogenous Braf promoter, and spontaneous PTC developed at about 5 weeks of age. The mice were subjected to two treatment regimens: (1) weekly intramuscular injection of 50 μg plasmid DNA expressing a single-chain IL-12 fusion protein (scIL-12/CMVpDNA), (2) daily intraperitoneal injection of mouse recombinant IL-12 protein (mrIL-12, 100 ng per day). The role of T cells, natural killer (NK) cells, and transforming growth factor-β (TGF-β) in IL-12-mediated antitumor effects was determined by a (51)Cr-release cytotoxicity assay. Tumor size and weight were significantly reduced by either weekly intramuscular injection of scIL-12/CMVpDNA or daily intraperitoneal injection of mrIL-12, and tumor became more localized. Survival was significantly increased when treatment started at 1 week of age as compared with that at the 6 weeks of age. Both NK and CD8(+) T cells were involved in the cytotoxicity against tumor cells and their antitumor activity was significantly reduced in tumor-bearing mice. TGF-β also inhibited the antitumor activity of NK and CD8(+) T cells. The immune suppression was completely reversed by IL-12 treatment and partially recovered by anti-TGF-β antibody. We conclude that both IL-12 gene therapy and recombinant protein therapy are effective against PTC. Given that the immune response is significantly suppressed in tumor-bearing mice and can be restored by IL-12, the current study raises a possibility of the application of IL-12 as an adjuvant therapy for thyroid cancer.

Charge-conversional zwitterionic copolymer as pH-sensitive shielding system for effective tumor treatment

A novel pH-responsive gene delivery system for tumor acidity-targeted pDNA delivery is prepared by introducing a rapid charge-conversional zwitterionic copolymer to the positive surface of PEI/pDNA complexes through electrostatic interaction. The shielding system (OEAL) consists of oligoethylenimine (OEI), poly(l-aspartate) (PBLA), and poly(l-lysine) (PLL). The charge-conversional behavior of the OEAL/PEI/DNA ternary complex is evaluated by zeta potential assay. The surface charges of the complexes can change from negative to positive in the pH range of 7.4-6.8. Under a simulative in vivo environment, OEAL/PEI/DNA exhibits promotion of cellular uptake by tumor cells and enhanced gene transfection efficiency because of its good charge-conversional properties. Antitumor experiments further show that the pH-responsive charge-conversional system can mediate a therapeutic gene that can induce tumor apoptosis (pKH3-rev-casp-3) to achieve effective tumor inhibition. Accordingly, OEAL can be regarded as a promising tumor microenvironment-sensitive gene delivery shielding system for antitumor therapy.

STATEMENT OF SIGNIFICANCE

This manuscript focused on the novel pH-responsive gene delivery system for tumor acidity-targeted pDNA delivery. The novel system is prepared by introducing a rapid charge-conversional zwitterionic copolymer, consisting of oligoethylenimine, poly(l-aspartate) and poly(l-lysine), to the positive surface of PEI/pDNA complexes. The surface charges of the complexes can change from negative to positive from pH 7.4 to 6.8. OEAL/PEI/DNA shows promoting cellular uptake by tumor cells and enhanced gene transfection efficiency. The antitumor experiments further show that the pH responsive charge conversional system can mediate pKH3-rev-casp-3 to achieve effective tumor inhibition. Accordingly, OEAL can be regarded as a promising tumor microenvironment sensitive gene delivery shielding system for antitumor therapy.

Down-regulation of TIMP-1 inhibits cell migration, invasion, and metastatic colonization in lung adenocarcinoma

Tissue inhibitor metalloproteinase-1 (TIMP-1) is clinically associated with a poor prognosis for various cancers, but the roles of TIMP-1 in lung cancer metastasis are controversial. Our previous secretomic study revealed that TIMP-1 is highly abundant in high invasiveness cells of lung adenocarcinoma. In the current study, TIMP-1 abundances in primary lung adenocarcinoma tissues, as revealed by immunohistochemistry, are significantly higher in patients with lymph invasion and distant metastasis than in those without. Receiver operating characteristic curve analyses suggest 73.7 and 86.2 % accuracy to separate patients with lymph node and distant metastasis and those without, respectively. Moreover, we demonstrate that the expression level of TIMP-1 positively associates with cell mobility, invasiveness, and metastatic colonization. Most notably, the novel mechanism in which TIMP-1 facilitates metastatic colonization through the mediation of pericellular polyFN1 assembly was revealed. In summary, this study presents novel functions of TIMP-1 in promoting cancer metastasis and suggests TIMP-1 is a potential tissue biomarker for lymph invasion and distant metastasis of lung adenocarcinoma.

Tissue inhibitor of metalloproteinase 1 expression associated with gene demethylation confers anoikis resistance in early phases of melanocyte malignant transformation

Although anoikis resistance has been considered a hallmark of malignant phenotype, the causal relation between neoplastic transformation and anchorage-independent growth remains undefined. We developed an experimental model of murine melanocyte malignant transformation, where a melanocyte lineage (melan-a) was submitted to sequential cycles of anchorage blockade, resulting in progressive morphologic alterations, and malignant transformation. Throughout this process, cells corresponding to premalignant melanocytes and melanoma cell lines were established and show progressive anoikis resistance and increased expression of Timp1. In melan-a melanocytes, Timp1 expression is suppressed by DNA methylation as indicated by its reexpression after 5-aza-2'-deoxycytidine treatment. Methylation-sensitive single-nucleotide primer extension analysis showed increased demethylation in Timp1 in parallel with its expression along malignant transformation. Interestingly, TIMP1 expression has already been related with negative prognosis in some human cancers. Although described as a MMP inhibitor, this protein has been associated with apoptosis resistance in different cell types. Melan-a cells overexpressing Timp1 showed increased survival in suspension but were unable to form tumors in vivo, whereas Timp1-overexpressing melanoma cells showed reduced latency time for tumor appearance and increased metastatic potential. Here, we demonstrated for the first time an increment in Timp1 expression since the early phases of melanocyte malignant transformation, associated to a progressive gene demethylation, which confers anoikis resistance. In this way, Timp1 might be considered as a valued marker for melanocyte malignant transformation.

C-C chemokine receptor 5 on stromal cells promotes pulmonary metastasis

We have shown that mice that express the C-C chemokine receptor 5 (CCR5) have enhanced local tumor growth and an impaired response to vaccine therapy compared with CCR5 knockout (CCR5(-/-)) mice. Here, we extend these observations to evaluate the function of CCR5 in pulmonary metastasis and the mechanism underlying the diminished tumor growth in CCR5(-/-) mice. Lung metastases were counted in wild-type (WT) and CCR5(-/-) mice following the injection of 1 x 10(6) B16-F10 melanoma cells. These results were compared with those from syngeneic bone marrow chimeric mice formed by the transfer of WT bone marrow into irradiated CCR5(-/-) and CCR5(-/-) marrow into irradiated WT mice. Intact CCR5(-/-) mice developed fewer metastases than WT mice (40.2 versus 70.6; P < 0.05). Bone marrow chimeras formed by the transfer of WT bone marrow into CCR5(-/-) hosts had fewer metastases than WT hosts injected with knockout marrow (46.6 versus 98.6; P < 0.01). Adoptive transfer of CCR5-expressing leukocytes also failed to promote metastasis in CCR5(-/-) mice. However, the i.v. transfer of WT pulmonary stromal cells into CCR5(-/-) mice increased the number of metastases compared with transfer of CCR5(-/-) stromal cells (102.8 versus 26.0; P < 0.05). These results show for the first time that CCR5 expression on stromal and not hematopoietic cells contributes to tumor metastasis. Therefore, recently developed CCR5 inhibitors may have a novel benefit in cancer therapy.

Gene therapy of anaplastic thyroid carcinoma with a single-chain interleukin-12 fusion protein

Anaplastic thyroid carcinoma is the most aggressive type of thyroid malignancy with a mean survival time of less than 8 months. No effective therapeutic approach is currently available, making the development of novel treatments necessary. Interleukin (IL)-12 is a proinflammatory heterodimeric cytokine with strong antitumor activity. In the present study, we investigated the potential of IL-12 gene therapy for anaplastic thyroid carcinoma in BALB/c (nu/nu) nude mice. A single-chain IL-12 fusion protein construct was created to assure equal expression of its p35 and p40 subunits. Human anaplastic thyroid carcinoma cell line ARO was stably transfected with an IL-12 expression plasmid under the control of cytomegalovirus (CMV) promoter (scIL-12/CMVpDNA). High levels of functional IL-12 (26.78 +/- 4.11 ng/ml per 10(6) cells per 48 hr) were produced by scIL-12-transfected ARO cells (ARO/IL-12). Tumorigenicity in nude mice was completely lost in scIL-12-transfected ARO cells, as demonstrated by the lack of tumor formation after subcutaneous injection of 2 x 10(6) ARO/IL-12 cells, even though there was no difference in cell proliferation between ARO and ARO/IL-12 cells. Tumor growth was observed after challenge with ARO tumor cells, indicating that protective immunity had not developed against the parental cells. Furthermore, the growth rate of established subcutaneous ARO tumors was significantly reduced by either subcutaneous injection of 2 x 10(6) ARO/IL-12 cells weekly or intramuscular injection of 50 microg scIL-12/CMVpDNA twice weekly. The antineoplastic activity of ARO/IL-12 cells was, however, abrogated by intraperitoneal injection of anti-natural killer (NK) cell antibody. Moreover, significantly higher number of ARO/IL-12 cells and ARO cells were killed by splenocytes from nude mice previously treated with ARO/IL-12 compared to those treated with ARO cells (32% vs. 9% when ARO were used as target cells, 43% vs. 17% when ARO/IL12 were used as target cells; p < 0.01) in an in vitro cytotoxicity assay. Again, tumor cell killing was neutralized by the addition of anti-NK cell antibody in the assay. In conclusion, we have demonstrated successful gene therapy with a scIL-12 fusion protein against anaplastic thyroid carcinoma in an in vivo model. The immune response against ARO/IL-12 cells is mediated by NK cells. These results may set the stage for clinical application of IL-12 gene therapy for poorly differentiated thyroid carcinoma.

Antitumor efficacy of reticulol from Streptoverticillium against the lung metastasis model B16F10 melanoma. Lung metastasis inhibition by growth inhibition of melanoma

Reticulol was isolated from the culture broth of the strain Streptoverticillium sp. NA-4803. Recticulol (M.W. 222.2) exhibited a potent in vitro cytotoxicity against A427, a human lung tumor cell line, and B16F10, a mouse melanoma cell line. In the trypan blue staining assay for B16F10 cells, the cell viability by reticulol treatment was significantly decreased in a dose-dependent manner. The in vivo assay for the lung metastasis-blocking effect showed that reticulol injected intravenously suppressed the increase in colonies on the lung in a dose-dependent manner. In addition, the survival rate of tumor-implanted mice treated with reticulol was closely associated with its antitumoral efficacy. Reticulol administered via the peritoneum of mice showed less metastasis inhibition than that injected intravenously. To demonstrate the mechanism for inhibition of metastasis, the inhibitory effect of reticulol for matrix metalloproteinase-2 or -9 involved in melanoma metastasis was investigated; however, they were not observed on zymogram gel. In addition, the antitumor efficacy of reticulol was not associated with cell cycle arrest or apoptosis. Therefore, it was inferred that reticulol known as a phosphodiesterase inhibitor directly inhibited the growth of B16F10 melanoma, showing necrotic response. These results suggest that reticulol protects its lung metastasis via the bloodstream by inhibiting the growth of B16F10 melanoma at the cellular level.