E. coli NfsA: an alternative nitroreductase for prodrug activation gene therapy in combination with CB1954

Prodrug activation gene therapy is a developing approach to cancer treatment, whereby prodrug-activating enzymes are expressed in tumour cells. After administration of a non-toxic prodrug, its conversion to cytotoxic metabolites directly kills tumour cells expressing the activating enzyme, whereas the local spread of activated metabolites can kill nearby cells lacking the enzyme (bystander cell killing). One promising combination that has entered clinical trials uses the nitroreductase NfsB from Escherichia coli to activate the prodrug, CB1954, to a potent bifunctional alkylating agent. NfsA, the major E. coli nitroreductase, has greater activity with nitrofuran antibiotics, but it has not been compared in the past with NfsB for the activation of CB1954. We show superior in vitro kinetics of CB1954 activation by NfsA using the NADPH cofactor, and show that the expression of NfsA in bacterial or human cells results in a 3.5- to 8-fold greater sensitivity to CB1954, relative to NfsB. Although NfsB reduces either the 2-NO2 or 4-NO2 positions of CB1954 in an equimolar ratio, we show that NfsA preferentially reduces the 2-NO2 group, which leads to a greater bystander effect with cells expressing NfsA than with NfsB. NfsA is also more effective than NfsB for cell sensitisation to nitrofurans and to a selection of alternative, dinitrobenzamide mustard (DNBM) prodrugs

Repeated cycles of Clostridium-directed enzyme prodrug therapy result in sustained antitumour effects in vivo

The unique properties of the tumour microenvironment can be exploited by using recombinant anaerobic clostridial spores as highly selective gene delivery vectors. Although several recombinant Clostridium species have been generated during the past decade, their efficacy has been limited. Our goal was to substantially improve the prospects of clostridia as a gene delivery vector. Therefore, we have assessed a series of nitroreductase (NTR) enzymes for their capacity to convert the innocuous CB1954 prodrug to its toxic derivative. Among the enzymes tested, one showed superior prodrug turnover characteristics. In addition, we established an efficient gene transfer procedure, based on conjugation, which allows for the first time genetic engineering of Clostridium strains with superior tumour colonisation properties with high success rates. This conjugation procedure was subsequently used to create a recombinant C. sporogenes overexpressing the isolated NTR enzyme. Finally, analogous to a clinical setting situation, we have tested the effect of multiple consecutive treatment cycles, with antibiotic bacterial clearance between cycles. Importantly, this regimen demonstrated that intravenously administered spores of NTR-recombinant C. sporogenes produced significant antitumour efficacy when combined with prodrug administration

‘Connecting the patriarchs: Noah and Abraham in the Old English Exodus’

The Old English poem Exodus narrates the flight of Moses and the Israelites from Egyptian captivity, joining the story at the moment the tenth plague strikes the Egyptians and concluding with the Hebrews celebrating the destruction of Pharaoh and his army by the Red Sea. Despite what is at times a highly allusive style, and some omissions from the Biblical narrative, the poem recounts the order of events much as they are presented in chapters 12–15 of the book of Exodus, apart from one point when the poet digresses to tell the story of Noah and the Flood (ll. 362–76) and of Abraham's sacrifice of Isaac (ll. 380–46). Their histories are told as the Israelite tribes are about to enter the Red Sea and in the context of a genealogical recollection of their national ancestry (ll. 353b–61), beginning with Noah and leaping the generations to Abraham (ll. 376–79). The suddenness of this departure from the Exodus narrative requires explanation, and critics have generally explained the "digression " in terms of the connection made in Christian theology between events of the patriarchs' lives and the history unfolding at the Red Sea. The Flood and the sacrifice of Isaac were both linked to the exodus in the theology of the early church as major Old Testament events typologically foreshadowing the salvation of the Christian faithful, a connection confirmed by the recollection of these events in the readings of the Easter liturgy, a festival also associated with the sacrament of Baptism

‘Sceaf, Japheth and the Origins of the Anglo-Saxons’

The Anglo-Saxons' awareness of their cultural and racial affiliation with their continental cousins is well attested, as is their interest in the earliest migrations of their ancestors to the British Isles from the homelands of northern Europe. The founding figures who led the migrations from Europe across the North Sea had names which were preserved by oral tradition well into the Christian period, and the names of these founders of Anglo-Saxon dynasties entered the historical record when Christian missionaries introduced the technology of writing among the Anglo-Saxons