Helene Z. Hill

Learn More
Cloudman S91 mouse melanoma cells vary in constitutive and inducible melanin levels. Survival, mutation induction and DNA damage were quantitated after exposure to UVB, UVA and FS20 lamps. Assuming that the observed differences are related to melanin, induced pigment is photo-protective for survival and mutation after UVB and FS20 exposure, and is(More)
To investigate the biological effects of nonuniform distribution of radioactivity in mammalian cells, we have developed a novel three-dimensional tissue culture model. Chinese hamster V79 cells were labeled with tritiated thymidine and mixed with unlabeled cells, and multicellular clusters (approximately 1.6 mm in diameter) were formed by gentle(More)
S-phase-active cytotoxic drugs selectively damage leukemic cells, but the mechanisms of this action are not clear. We have investigated the previously reported potentiation of toxicity of 1-beta-D-arabinofuranosylcytosine (ara-C) to HL-60 cells by the differentiation-inducing steroid, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and compared the results with the(More)
When the Auger-electron emitter, 55Fe, and the beta-emitter, 59Fe, are similarly distributed in the testes of mice, the conventionally calculated average radiation dose to the organ from 55Fe is about 2.6 times more effective in reducing the sperm-head count than the dose from 59Fe. This finding emphasizes the ability of low-energy Auger electrons to damage(More)
The results of three Phase III studies of DTIC in 580 patients with metastatic melanoma were reviewed to evaluate the subsequent course of 26 patients who achieved a complete response (CR) to chemotherapy. The majority (17 of 26) of these patients had soft tissue metastases. Six of the 26 patients remained in CR at last report (30-259 weeks), two died of(More)
Synthetic eumelanin prepared by autooxidation of D,L-DOPA causes DNA strand breaks, as determined by alkaline elution after cell lysis with detergent and proteolysis, in B16CL4 mouse melanoma cells. The melanin is toxic to the cells in the range of doses that causes strand breaks. When the melanin was incubated with the cells at 37 degrees C in tissue(More)
Solar radiation can lead to changes affecting DNA metabolism resulting in loss of DNA integrity. Skin specimens obtained from melanoma patients treated at the Memorial Sloan-Kettering Cancer Center were used to study patterns of DNA fragmentation using the comet assay and levels of deletions in mitochondrial DNA (mtDNA) using real-time PCR. Skin specimens(More)
A rapid nonsterile short-term assay has been investigated in which percent inhibition of incorporation of the DNA precursor (3H)-thymidine is measured following exposure of tumor cells to the test drugs. To evaluate the usefulness of the short-term assay in providing a rapid reliable assessment of chemotherapeutic response, the short-term assay was compared(More)
Melanin is both photosensitizer and photoprotector. Skin cancer rates decrease with increasing constitutive pigmentation, yet the pigment has been shown to be photoreactive and capable of producing damaging reactive oxygen species. We utilized model systems of related cells or similar cell type that vary in constitutive and in induced pigment. Induction of(More)
The relationship between cell pigmentation and radiosensitivity was investigated in two selected human melanoma cell lines with different melanin content (mixed type: eumelanin and pheomelanin, and pheomelanotic phenotypes). The same study was also done after stimulation of melanogenesis (1) by addition of the melanin precursor l-tyrosine to each of the(More)