Effects of miRNA-15 and miRNA-16 expression replacement in chronic lymphocytic leukemia: implication for therapy.

Chronic lymphocytic leukemia (CLL) clones are characterized by loss of a critical region in 13q14.3, (del(13)(q14)) involving the microRNA (miRNA) cluster miR-15a and miR-16-1. We have investigated the effects of replacement of miR-15a and miR-16-1. CLL cells transfected with these miRNA mimics exhibited a decrease in cell viability in vitro and impaired capacity for engraftment and growth in NOD/Shi-scid,γcnull (NSG) mice. No synergistic effects were observed when the two miRNA mimics were combined. The phenomena were not restricted to CLL with the del(13)(q14) lesion. Similar effects induced by miRNA mimics were seen in cells with additional chromosomal abnormalities with the exception of certain CLL clones harboring TP53 alterations. Administration of miRNA mimics to NSG mice previously engrafted with CLL clones resulted in substantial tumor regression. CLL cell transfection with miR-15a and miR-16-1-specific inhibitors resulted in increased cell viability in vitro and in an enhanced capacity of the engrafted cells to grow in NSG mice generating larger splenic nodules. These data demonstrate that the strong control by miR-15a and miR-16-1 on CLL clonal expansion is exerted also at the level of full-blown leukemia and provide indications for a miRNA-based therapeutic strategy.

Fibroblasts regulate the migration of MCF7 mammary carcinoma cells in hydrated collagen gel.

We have defined a tissue culture method suitable to study cell-cell interactions in an environmental set close to in vivo conditions. It consists of heterotypic cell populations mixed together inside a collagen gel in a chamber slide for a period of up to 14 days. When the three-dimensional system is saturated, cells will start to move on the plastic surface as monolayers surrounding the gel, with a characteristic speed depending on cell type. Usually fibroblasts move fast, while epithelial cells demonstrate a much lower pace of migration. At any given time gel contraction can be measured, and thus the rate of cell expansion, by knowing the distance from the edge of the gel to the leading edge of cell migration. By using this approach it was found that MCF7 mammary carcinoma cells display a great variety of morphologies following their mixture with different fibroblastic cell lines. In particular, when MCF7 cells were mixed with fibroblasts from human fetus, dog thymus and rat kidney, they migrated up to the leading edge of the fibroblastic front as isolated single cells or as cellular aggregates, many of which became necrotic in time, or took on an elongated morphology. Selective necrosis of MCF7 cells was also induced with serum concentration of 15% and 20% FCS, but only when they were mixed with fibroblasts. No necrosis was induced in MCF7 cells cultured alone. From these observations it is suggested that necrosis may sometimes favor the detachment and infiltration of resistant epithelial tumor cells by increasing their autonomous behaviour. Fibroblasts seem to be instrumental in regulating this process.

[Malignant melanoma of nasal cavities. Case contributions]. / Il melanoma maligno delle fosse nasali. Contributo casistico.

Primitive melanoma of nasal cavities is a rare clinical event. Its pathogenesis is due to the neoplastic development of melanocytes of neuroectodermal origin which are located in the nasal mucosa. Characteristics clinical symptoms are nasal obstruction and recurrent nose-bleeding. In spite of new therapeutic approaches the prognosis of this disease remains severe. No case of primitive malignant melanoma of the nasal cavities has been treated with radiotherapy, according to the authors experience. Sometimes it may be difficult to recognize a cutaneous malignant melanoma because of regression. It may be found after the evidentiation of its recurrences and/or metastasis in different sites. One of the cases here reported came to the authors' attention as ethmoido-frontal metastasis.

Co-culture with human fibroblasts increases the radiosensitivity of MCF-7 mammary carcinoma cells in collagen gels.

The growth and differentiation of normal and neoplastic epithelial cells may be regulated by the presence of adjacent normal tissues and cells, particularly stromal fibroblasts. However, the influence of normal fibroblast-tumor cell interactions on the response of malignant epithelial cells to radiation has not been adequately investigated nor has the possible role played by a 3-D environment in such modulation. We addressed this question by embedding MCF-7 mammary carcinoma cells into a collagen lattice, alone or mixed with HSF human dermal fibroblasts, and kept the gels anchored to the plastic surface or suspended in the culture medium. Some gels served as controls and others were irradiated with 6 MV photons fractionated into 3 daily doses totaling 5 or 10 Gy. After 2 or 7 days from the last treatment (7 or 12 days in culture, respectively), gels were processed in 1 of 2 ways: overall cell survival was determined by the MTT assay, while the survival of MCF-7 cells was selectively detected by a clonogenicity assay. Under these experimental conditions, we found that, in the presence of HSF fibroblasts, the growth of MCF-7 cells was restrained and radiosensitivity increased compared with MCF-7 cells cultured alone. For example, while the average number of MCF-7 foci/gel recovered from control gels with MCF-7 cells alone was 2,460 on day 7 and 3, 290 on day 12 of culture, it was 4 to 5 times lower (p < 0.001) in control gels with mixed MCF-7 and HSF cells. Radiation affected severely the survival of MCF-7 cells in all experimental groups but not sufficiently to mask the differences. For example, following exposure to the low dose of 5 Gy, the average number of MCF-7 foci/gel recovered from MCF-7-containing gels was 590 on day 7 and 329 on day 12 of culture, whereas numbers from the gels containing mixed MCF-7 and HSF cells were only 218 and 73, respectively (p < 0. 003 in both cases). HSF fibroblasts did not grow in our system, but they contracted strongly anchored and floating gels.