Cetuximab delivery and antitumor effects are enhanced by mild hyperthermia in a xenograft mouse model of pancreatic cancer.

Even with current promising antitumor antibodies, their antitumor effects on stroma-rich solid cancers have been insufficient. We used mild hyperthermia with the intent of improving drug delivery by breaking the stromal barrier. Here, we provide preclinical evidence of cetuximab + mild hyperthermia therapy. We used four in vivo pancreatic cancer xenograft mouse models with different stroma amounts (scarce, MIAPaCa-2; moderate, BxPC-3; and abundant, Capan-1 and Ope-xeno). Cetuximab (1 mg/kg) was given systemically, and the mouse leg tumors were concurrently heated using a water bath method for 30 min at three different temperatures, 25°C (control), 37°C (intra-abdominal organ level), or 41°C (mild hyperthermia) (n = 4, each group). The evaluated variables were the antitumor effects, represented by tumor volume, and in vivo cetuximab accumulation, indirectly quantified by the immunohistochemical fluorescence intensity value/cell using antibodies against human IgG Fc. At 25°C, the antitumor effects were sufficient, with a cetuximab accumulation value (florescence intensity/cell) of 1632, in the MIAPaCa-2 model, moderate (1063) in the BxPC-3 model, and negative in the Capan-1 and Ope-xeno models (760, 461). By applying 37°C or 41°C heat, antitumor effects were enhanced shown in decreased tumor volumes. These enhanced effects were accompanied by boosted cetuximab accumulation, which increased by 2.8-fold (2980, 3015) in the BxPC-3 model, 2.5- or 4.8-fold (1881, 3615) in the Capan-1 model, and 3.2- or 4.2-fold (1469, 1922) in the Ope-xeno model, respectively. Cetuximab was effective in treating even stroma-rich and k-ras mutant pancreatic cancer mouse models when the drug delivery was improved by combination with mild hyperthermia.

Visualization analysis of the vacuole-targeting fungicidal activity of amphotericin B against the parent strain and an ergosterol-less mutant of Saccharomyces cerevisiae.

Here, we sought to investigate the vacuole-targeting fungicidal activity of amphotericin B (AmB) in the parent strain and AmB-resistant mutant of Saccharomyces cerevisiae and elucidate the mechanisms involved in this process. Our data demonstrated that the vacuole-targeting fungicidal activity of AmB was markedly enhanced by N-methyl-N″-dodecylguanidine (MC12), a synthetic analogue of the alkyl side chain in niphimycin, as represented by the synergy in their antifungal activities against parent cells of S. cerevisiae. Indifference was observed only with Δerg3 cells, indicating that the replacement of ergosterol with episterol facilitated their resistance to the combined lethal actions of AmB and MC12. Dansyl-labelled amphotericin B (AmB-Ds) was concentrated into normal rounded vacuoles when parent cells were treated with AmB-Ds alone, even at a non-lethal concentration. The additional supplementation of MC12 resulted in a marked loss of cell viability and vacuole disruption, as judged by the fluorescence from AmB-Ds scattered throughout the cytoplasm. In Δerg3 cells, AmB-Ds was scarcely detected in the cytoplasm, even with the addition of MC12, reflecting its failure to normally incorporate across the plasma membrane into the vacuole. Thus, this study supported the hypothesis that ergosterol is involved in the mobilization of AmB into the vacuolar membrane so that AmB-dependent vacuole disruption can be fully enhanced by cotreatment with MC12.