Peter H. Clingen

2566 Background: This phase I study was undertaken to define dose-limiting toxicity (DLT) and maximum tolerated dose (MTD) of the pyrrolobenzodiazepine dimer SJG-136 in patients with advanced solid tumors. Methods: Good performance patients (PS ≤1) with refractory advanced solid tumors were assigned sequentially to escalating doses of SJG-136 (15 to 240 μg/m²) given as a 10-minute intravenous infusion once every 21 days. An accelerated dose-escalation strategy based on the Simon design was used. Results: 16 patients (11M, 5F) median age 70 years for M (range 41–79) and 56 for F (range 54–58) recruited. Cancer sites included biliary (2), colorectal (5), lung (1), oesophagogastric (2), pancreas (2), sarcoma (1), melanoma (3). Dose levels μg/m²) were 15 (1 pt), 30 (1 pt), 45 (7 pt), 60 (4 pt) 120 (2 pt), 240 (1 pt). 10 pts had grade 1–3 VLS (30–240 μg/m²) with Gr 3 occurring at the top doses at 120 and 240 in 2 pts. DLT were a delayed vascular leak syndrome (DVLS) seen in 4 of 5 pts treated at doses between 30 and 240 μg/m². DVLS was characterized by hypoalbuminemia, oedema, and other features included pleural effusion, dyspnoea, weight gain and abdominal distension. The dose was reduced to 60 μg/m² but 2/3 pts developed delayed, prolonged liver toxicity. 7 pts were recruited at a dose level of 45 μg/m² in combination with dexamethasone, starting 24 hours before treatment to prevent DVLS. Other unexpected adverse events included elevated liver function tests and fatigue. 10 patients had stable disease for > 6 weeks, 2 patients for > 12 weeks. There was no evidence of crosslinking using the single cell gel electrophoresis (comet) assay. Evidence of DNA interstrand cross-linking in peripheral lymphocytes and tumour cells was demonstrated at all dose levels using a sensitive gamma-H2AX assay. SJG-136 demonstrated biphasic clearance and linear pharmacokinetics across the dose range tested. Conclusions: When given as a single injection every 21 days, the MTD for SJG-136 is 45 μg/m² but a recommended dose for phase II testing was not identified. The major DLT was DVLS, but delayed liver toxicity was also observed. DNA damage was noted at all dose levels studied in circulating lymphocytes and tumour. Alternative clinical dosing strategies are now being evaluated. No significant financial relationships to disclose.

Background Recent studies have demonstrated that a tanning lamp emitting predominantly ultraviolet (UV) A induces significant yields of the type of potentially mutagenic DNA damage that are associat...

We have compared the induction of apoptosis and cytokine release by UVB and gamma-radiation in primary (untransformed) and in two immortalized human epithelial/keratinocyte cell lines, HaCaT and KB (KB is now known to be a subline of the ubiquitous keratin-forming tumour cell line HeLa and we therefore designate it HeLa-KB). In both the primary and the immortalized cell lines apoptosis and release of the inflammatory cytokine interleukin-6 are induced rapidly following UVB irradiation. In contrast, only the immortalized cells undergo apoptosis and release interleukin-6 after gamma-irradiation and here the onset of apoptosis and cytokine release are delayed. The same distinction between primary and immortalized cells was observed when double-strand breaks were induced with the anticancer drug mitoxantrone, which stabilizes topoisomerase II-cleavable complexes. We suggest that immortalization may sensitize keratinocytes to the apoptogenic effect of ionizing radiation or mitoxantrone by deregulating normal cell cycle checkpoints. In both human keratinocytes and fibroblasts, cell killing, as assayed by loss of colony-forming ability, is not coupled to apoptosis. Immortalization increases resistance to gamma-radiation killing but sensitizes to apoptosis. In contrast, although immortalization also sensitizes to UVB-induced apoptosis, it does not affect UVB-induced cell killing. Apoptosis unambiguously indicates death at the single cell level but clonal cell survival integrates all the cellular and genetic processes which prevent or permit a scorable clone to develop.

The DNA repair-deficient genetic disorders xeroderma pigmentosum (XP) and trichothiodystrophy (TTD) can both result from mutations in the XPD gene, the sites of the mutations differing between the two disorders. The hallmarks of XP are multiple pigmentation changes in the skin and a greatly elevated frequency of skin cancers, characteristics that are not seen in TTD. XP-D and most TTD patients have reduced levels of DNA repair, but some recent reports have suggested that the repair deficiencies in TTD cells are milder than in XP-D cells. We reported recently that inhibition of intracellular adhesion molecule-1 (ICAM-1) expression by UVB irradiation was similar in normal and TTD cells but increased in XP-D cells, suggesting a correlation between ICAM-1 inhibition and cancer proneness. In the first part of the current work, we have extended these studies and found several other examples, including XP-G and Cockayne syndrome cells, in which increased ICAM-1 inhibition correlated with cancer proneness. However, we also discovered that a subset of TTD cells, in which arg112 in the NH2-terminal region of the XPD protein is mutated to histidine, had an ICAM-1 response similar to that of XP-D cells. In the second part of the work, we have shown that TTD cells with this specific NH2-terminal mutation are more sensitive to UV irradiation than other TTDs, most of which are mutated in the COOH-terminal region, and are indistinguishable from XP-D cells in cell killing, incision breaks, and repair of cyclobutane pyrimidine dimers. Because the clinical phenotypes of these patients do not obviously differ from those of TTDs with mutations at other sites, we conclude that the lack of skin abnormalities in TTD is independent of the defective cellular responses to UV. It is likely to result from a transcriptional defect, which prevents the skin abnormalities from being expressed.

Immunocytochemistry was used for the direct measurement of cyclobutane pyrimidine dimers, (6-4) photoproducts, and Dewar isomers in normal human mononuclear cells following irradiation by natural sunlight or by a FS20 broad spectrum UVB sunlamp. The induction of each type of photoproduct was detected following 30-60 min sunlight exposure or with FS20 fluences as low as 50-100 Jm-2. With increasing FS20 fluences, there was a dose-dependent increase in the binding of pyrimidine dimer, (6-4) photoproduct, and Dewar isomer-specific monoclonal antibodies. The relative ratio of Dewar isomer to (6-4) photoproduct antibody binding sites was much higher following exposure to natural sunlight than to broad spectrum UVB. With the (6-4) monoclonal antibody, a small increase in binding sites was evident after a 1-h exposure to natural sunlight. This remained relatively constant with further exposure. These results are consistent with the hypothesis that, following irradiation with natural sunlight, the majority of (6-4) photoproducts are converted into Dewar valence isomers.