BackgroundPreclinical evidence shows that short-term fasting (STF) protects healthy cells against side effects of chemotherapy and makes cancer cells more vulnerable to it. This pilot study examines the feasibility of STF and its effects on tolerance of chemotherapy in a homogeneous patient group with early breast cancer (BC).MethodsEligible patients had HER2-negative, stage II/III BC. Women receiving (neo)-adjuvant TAC (docetaxel/doxorubicin/cyclophosphamide) were randomized to fast 24 h before and after commencing chemotherapy, or to eat according to the guidelines for healthy nutrition. Toxicity in the two groups was compared. Chemotherapy-induced DNA damage in peripheral blood mononuclear cells (PBMCs) was quantified by the level of γ-H2AX analyzed by flow cytometry.ResultsThirteen patients were included of whom seven were randomized to the STF arm. STF was well tolerated. Mean erythrocyte- and thrombocyte counts 7 days post-chemotherapy were significantly higher (P = 0.007, 95 % CI 0.106-0.638 and P = 0.00007, 95 % CI 38.7-104, respectively) in the STF group compared to the non-STF group. Non-hematological toxicity did not differ between the groups. Levels of γ-H2AX were significantly increased 30 min post-chemotherapy in CD45 + CD3- cells in non-STF, but not in STF patients.ConclusionsSTF during chemotherapy was well tolerated and reduced hematological toxicity of TAC in HER2-negative BC patients. Moreover, STF may reduce a transient increase in, and/or induce a faster recovery of DNA damage in PBMCs after chemotherapy. Larger studies, investigating a longer fasting period, are required to generate more insight into the possible benefits of STF during chemotherapy.Trial registrationClinicalTrials.gov: NCT01304251, March 2011Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1663-5) contains supplementary material, which is available to authorized users.

The Rev3 gene of Saccharomyces cerevisiae encodes the catalytic subunit of DNA polymerase that is implicated in mutagenic translesion synthesis of damaged DNA. To investigate the function of its mouse homologue, we have generated mouse embryonic stem cells and mice carrying a targeted disruption of Rev3. Although some strain-dependent variation was observed, Rev3 ؊/؊ embryos died around midgestation, displaying retarded growth in the absence of consistent developmental abnormalities. Rev3 ؊/؊ cell lines could not be established, indicating a cell-autonomous requirement of Rev3 for long-term viability. Histochemical analysis of Rev3 ؊/؊ embryos did not reveal aberrant replication or cellular proliferation but demonstrated massive apoptosis in all embryonic lineages. Although increased levels of p53 are detected in Rev3 ؊/؊ embryos, the embryonic phenotype was not rescued by the absence of p53. A significant increase in double-stranded DNA breaks as well as chromatid and chromosome aberrations was observed in cells from Rev3 ؊/؊ embryos. The inner cell mass of cultured Rev3 ؊/؊ blastocysts dies of a delayed apoptotic response after exposure to a low dose of N-acetoxy-2-acetylaminofluorene. These combined data are compatible with a model in which, in the absence of polymerase , double-stranded DNA breaks accumulate at sites of unreplicated DNA damage, eliciting a p53-independent apoptotic response. Together, these data are consistent with involvement of polymerase in translesion synthesis of endogenously and exogenously induced DNA lesions.In cancer genetics, the paradigm holds the sequential mutation of a series of oncogenes and tumor suppressor genes responsible for the evolutionary development of a normal cell into a fully malignant, metastasizing tumor (67). Most mutations are induced by nucleotide damage, originating from endogenous sources or inflicted by exogenous agents (49). Nucleotide damage that is not removed by DNA repair proteins generally leads to an arrest of the replication fork, due to the rigidity of the replicative polymerases, preventing incorporation of a nucleotide opposite a damaged template (51). To escape this arrest, cells possess multiple pathways that enable the completion of DNA replication despite the presence of replication-blocking DNA damage (3, 9).Considerable progress has recently been made in identifying the actors in translesion synthesis, a pathway implicated in replicating damaged DNA. In both prokaryotes and eukaryotes, multiple polymerases have been identified that are capable of replicating DNA templates containing a variety of lesions. This enables the completion of replication and therefore safeguards cellular survival, albeit frequently at the expense of the introduction of mutations. Based on sequence homology and activity in vitro, most of the polymerases associated with translesion synthesis belong to the newly recognized Y superfamily of DNA polymerases (16,21,30,32,57,70). The heterodimeric Saccharomyces cerevisiae polymerase , comprised of the REV3 catalytic subun...

Hazard assessment, based on new approach methods (NAM), requires the use of batteries of assays, where individual tests may be contributed by different laboratories. A unified strategy for such collaborative testing is presented. It details all procedures required to allow test information to be usable for integrated hazard assessment, strategic project decisions and/or for regulatory purposes. The EU-ToxRisk project developed a strategy to provide regulatorily valid data, and exemplified this using a panel of > 20 assays (with > 50 individual endpoints), each exposed to 19 well-known test compounds (e.g. rotenone, colchicine, mercury, paracetamol, rifampicine, paraquat, taxol). Examples of strategy implementation are provided for all aspects required to ensure data validity: (i) documentation of test methods in a publicly accessible database; (ii) deposition of standard operating procedures (SOP) at the European Union DB-ALM repository; (iii) test readiness scoring accoding to defined criteria; (iv) disclosure of the pipeline for data processing; (v) link of uncertainty measures and metadata to the data; (vi) definition of test chemicals, their handling and their behavior in test media; (vii) specification of the test purpose and overall evaluation plans. Moreover, data generation was exemplified by providing results from 25 reporter assays. A complete evaluation of the entire test battery will be described elsewhere. A major learning from the retrospective analysis of this large testing project was the need for thorough definitions of the above strategy aspects, ideally in form of a study pre-registration, to allow adequate interpretation of the data and to ensure overall scientific/toxicological validity.

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