High incidence of chromosomal lesions involving C-heterochromatin in four human melanoma lines

Neutrophils are a key component of the antitumor efficacy of topical chemotherapy with ingenol-3-angelate

Harnessing neutrophils for the eradication of cancer cells remains an attractive but still controversial notion. In this study, we provide evidence that neutrophils are required to prevent relapse of skin tumors following topical treatment with a new anticancer agent, ingenol-3-angelate (PEP005). Topical PEP005 treatment induces primary necrosis of tumor cells, potently activates protein kinase C, and was associated with an acute T cell-independent inflammatory response characterized by a pronounced neutrophil infiltrate. In Foxn1(nu) mice depleted of neutrophils and in CD18-deficient mice (in which neutrophil extravasation is severely impaired) PEP005 treatment was associated with a >70% increase in tumor relapse rates. NK cell or monocyte/macrophage deficiency had no effect on relapse rates. Both in vitro and in mice, PEP005 induced MIP-2/IL-8, TNF-alpha, and IL-1beta, all mediators of neutrophil recruitment and activation. In vitro, PEP005 activated human endothelial cells resulting in neutrophil adhesion and also induced human neutrophils to generate tumoricidal-reactive oxygen intermediates. Treatment of tumors with PEP005 significantly elevated the level of anticancer Abs, which were able to promote neutrophil-mediated Ab-dependent cellular cytotoxicity (ADCC) in vitro. PEP005 treatment of tumors grown in SCID mice was also associated with >70% increase in tumor relapse rates. Taken together, these data suggest a central role for neutrophil-mediated ADCC in preventing relapse. PEP005-mediated cure of tumors therefore appears to involve initial chemoablation followed by a neutrophil-dependent ADCC-mediated eradication of residual disease, illustrating that neutrophils can be induced to mediate important anticancer activity with specific chemotherapeutic agents.

Loss of Y chromosome with retention of Y heterochromatin in a marker chromosome from a human melanoma

A single copy of a der 15 chromosome (m3) characterized by a C- and distamycin A-Dapi-positive region was observed in the -Y hyperploid karyotype of a primary human melanoma (Me 1402). The heterochromatic region was located pericentromerically, adjacent at one end to the NOR region of chromosome 15, and at the other to an unclassifiable chromosomal piece. We established that the C-positive block in the marker chromosome originated from Y heterochromatin by high-stringency in situ hybridization with a DNA probe for the 2.1 Hae III Y-specific repeat. Loss of the Y chromosome in tumors has been considered to be a secondary event associated with malignant evolution. It is significant that Me 1402 cells, which are highly malignant, lack the Y chromosome, but retain its heterochromatic portion in the rearranged m3 chromosome.