Monitoring of somatic mutations in circulating cell-free DNA by digital PCR and next-generation sequencing during afatinib treatment in patients with lung adenocarcinoma positive for EGFR activating mutations.

Background: Analysis of circulating cell-free DNA (cfDNA) is under intensive investigation for its potential to identify tumor somatic mutations. We have now explored the usefulness of such liquid biopsy testing with both the digital polymerase chain reaction (dPCR) and next-generation sequencing (NGS) during treatment of patients with the epidermal growth factor receptor (EGFR) inhibitor afatinib. Patients and methods: Eligible patients had advanced lung adenocarcinoma with EGFR activating mutations and were treated with afatinib. Plasma samples were collected before and during (4 and 24 weeks) afatinib treatment as well as at disease progression. Tumor and plasma DNA were analyzed by dPCR and NGS. Results: Thirty-five patients were enrolled. The objective response rate and median progression-free survival (PFS) were 77.1% and 13.8 months, respectively. Tumor and plasma DNA were available for 32 patients. dPCR and NGS detected EGFR activating mutations in 81.3% and 71.9% of baseline cfDNA samples, respectively. In 19 patients treated with afatinib for ≥24 weeks, the number of EGFR mutant alleles detected in cfDNA by dPCR declined rapidly and markedly after treatment onset, becoming undetectable or detectable at only a low copy number (<10 copies per milliliter) at 4 weeks. Median PFS was slightly longer for patients with undetectable EGFR mutant alleles in cfDNA at 4 weeks than for those in whom such alleles were detectable (14.3 versus 10.0 months). A total of 45 somatic mutations was identified in baseline tumor DNA, and 30 (66.7%) of these mutations were identified in cfDNA by NGS. Allele frequency for somatic mutations in cfDNA determined by NGS changed concordantly during afatinib treatment with the number of EGFR mutant alleles determined by dPCR. Conclusions: Monitoring of cfDNA by dPCR is informative for prediction of afatinib efficacy, whereas that by NGS is reliable and has the potential to identify mechanisms of treatment resistance.

Ontogenetic diet shift of age-0 year Pacific bluefin tuna Thunnus orientalis.

Stomach contents of 437 age-0 year Pacific bluefin tuna Thunnus orientalis (20·3-59·4 cm fork length, L(F)) caught in the Tsushima Current and the Kuroshio regions around Japan were examined to investigate their ontogenetic diet shift. Prey compositions were diverse and different between regions. Although the seasonal growth patterns were different between regions, ontogenetic diet shifts shared a common pattern. In the Tsushima Current region (Sea of Japan), small T. orientalis (20-25 cm L(F)) preyed upon small squid (juvenile Enoploteuthis chunii), and larger ones (25-35 cm L(F)) gradually shifted their diet to mesopelagic fish (Maurolicus japonicus). In the Kuroshio region (Pacific Ocean), small T. orientalis (20-25 cm L(F)) preyed upon small zooplankton (mostly crustacean larvae), and larger ones (25-40 cm L(F)) shifted to epipelagic fishes (Etrumeus teres, Sardinops melanostictus and Engraulis japonicus). The observed data suggest that T. orientalis switch to a diet more based on fish prey items, which have more body mass and greater swimming ability than small squid and zooplankton, after they reach a L(F) of 25 cm.

Age and growth of albacore Thunnus alalunga in the North Pacific Ocean.

The age and growth of North Pacific albacore Thunnus alalunga were investigated using obliquely sectioned sagittal otoliths from samples of 126 females and 148 males. Otolith edge analysis indicated that the identified annulus in a sagittal otolith is primarily formed during the period from September to February. The assessments of the fish age at first annulus formation indicated that the first annulus represents an age of <1 year. This study presents an age estimate (0·75 years) for the formation of the first annulus. The oldest fish ages observed in this study were 10 years for females and 14 years for males. The von Bertalanffy growth parameters of females estimated were L(∞) = 103·5 cm in fork length (L(F) ), K = 0·340 year(-1) and t(0) = -0·53 years, and the parameters of males were L(∞) = 114·0 cm, K = 0·253 year(-1) and t(0) = -1·01 years. Sexual size dimorphism between males and females seemed to occur after reaching sexual maturity. The coefficients of the power function for expressing the L(F) -mass relationship obtained from sex-pooled data were a = 2·964 × 10(-5) and b = 2·928.

Habitat and food partitioning of billfishes (Xiphioidei).

Species composition and food habits of four istiophorid billfishes were investigated and compared in three different tropical areas of the eastern North Pacific Ocean by longline operations from September to November 2004. Sailfish Istiophorus platypterus, shortbill spearfish Tetrapturus angustirostris and blue marlin Makaira nigricans had specific habitat preferences and mainly occurred in the near-continent area (13-16 degrees N; 103-107 degrees W), the open-ocean area (16-18 degrees N; 118-134 degrees W) and the near-equator area (5 degrees N; 104-120 degrees W). Small (<140 cm in lower jaw-fork length) striped marlin Kajikia audax mainly occurred in the near-continent area; however, large (>/=140 cm) individuals occurred throughout all three areas. Prey compositions of large K. audax in the three areas were different from one other reflecting the prey availability in each area. In the open-ocean area, molid fishes were dominant in mass for both large K. audax (49%) and T. angustirostris (73%), and large K. audax also fed on ostraciid (33%) and scombrid fishes (15%). In the near-continent area, tetraodontid fishes were dominant for large and small I. platypterus (54, 57%), and both large and small K. audax also fed on tetraodontid fishes (3, 12%). Large K. audax in this area fed mainly on scombrid fishes (86%). These results indicate that large K. audax show overlaps but little segregations of its prey with other billfishes. In the near-equator area, stomach contents of large K. audax and M. nigricans were few and billfish prey items were thought to be scarce.