Detection and localization of early- and late-stage cancers using platelet RNA

Cancer patients benefit from early tumor detection since treatment outcomes are more favorable for less advanced cancers. Platelets are involved in cancer progression and are considered a promising biosource for cancer detection, as they alter their RNA content upon local and systemic cues. We show that tumor-educated platelet (TEP) RNA-based blood tests enable the detection of 18 cancer types. With 99% specificity in asymptomatic controls, thromboSeq correctly detected the presence of cancer in two-thirds of 1,096 blood samples from stage I–IV cancer patients and in half of 352 stage I–III tumors. Symptomatic controls, including inflammatory and cardiovascular diseases, and benign tumors had increased false-positive test results with an average specificity of 78%. Moreover, thromboSeq determined the tumor site of origin in five different tumor types correctly in over 80% of the cancer patients. These results highlight the potential properties of TEP-derived RNA panels to supplement current approaches for blood-based cancer screening

Potential life history costs of parasitoid avoidance in Drosophila melanogaster

Pupal parasitoids are a common natural enemy of Drosophila. As Drosophila pupae do not have an immunological defence against pupal parasitoids, they have to avoid being attacked. As a first step to identifying the costs of avoidance of parasitism by pupal parasitoids, we explored three traits that potentially influence the probability of D. melanogaster pupae to survive attack by Pachycrepoideus vindemiae. We found that larvae pupating on the food source had a higher probability of avoiding parasitism, but that the distance that larvae pupate away from the food had no effect on survival probability when exposed to pupal parasitoids. We also found no indication that the thickness of the puparial wall influences risk of parasitism. Pupal size, however, was correlated with the probability of surviving parasitoid attack, with smaller pupae having a higher survival probability. If pupal size is indeed the key trait influencing risk of parasitism of D. melanogaster pupae by P. vindemiae, the potential life-history costs of parasitoid avoidance are smaller adult size, leading to lower general fitnes

Host preference and survival in selected lines of a Drosophila parasitoid, Asobara tabida

Host selection behaviour of parasitoids has important fitness consequences, if hosts of different quality are available. Here the host selection behaviour, the ability to distinguish between hosts differing in their suitability, of the Drosophila parasitizing wasp Asobara tabida was studied. Females from five lines selected for higher survival in the encapsulating host species D. melanogaster (Kraaijeveld et al., 2001) were compared with females from control lines. Females from all five selected lines more readily accepted the encapsulating host species for oviposition when offered together with a nonencapsulating host species than females from the control lines. We found no evidence for pleiotropic effects and suggest that host selection behaviour evolved parallel to the ability to escape encapsulation in the hosts. Our results also suggest that given the appropriate selection pressures, host selection behaviour can quickly evolve in parasitoids, enabling them to adapt fast to changing circumstances

Is there local adaptation in Drosophila-parasitoid interactions?

Local adaptation has received little attention in host-parasitoid associations. Here we combine data on the outcome of parasitism in 20 sympatric populations of Drosophila melanogaster and its parasitoid Asobara tabida. We present data on resistance and virulence when each host is tested against a single allopatric strain of parasitoid, and when each parasitoid is tested against a single allopatric strain of host. We argue that the extent to which these allopatric interactions can be used to predict sympatric interactions sets an upper bound to the importance of local adaptation. In a statistical model, we found that 56% of the variance in the outcome of sympatric interactions could be explained by parasitoid virulence and host resistance measured using the allopatric reference strains, with the former being the much more important of the two. The geographical distance between the provenances of the sympatric and reference parasitoid (but not host) populationswas also statistically significant and increased the variance explained to69%; but against expectation, parasitoid success was negatively correlatedwith distance. We also explore the factors determining the frequency with which neither host nor parasitoid survive. We conclude that, although the critical tests have yet to be performed, the available evidence points towards local adaptation not being of major importance in this system

Basis of the trade off between parasitoid resistance and larval competitive ability in Drosophila melanogaster

Drosophila melanogaster can be artificially selected for increased resistance against parasitoid wasps that attack the larvae. Lines selected for greater resistance are poorer larval competitors under conditions of resource scarcity. Here we investigated the mechanistic basis of this apparent trade-off. We found that resistant lines have approximately twice the density of haemocytes (blood cells) than that of controls. Haemocytes are involved in encapsulation, the chief cellular immune defence against parasitoids. We have previously shown that resistant lines feed more slowly than controls and hypothesize that limiting resources are being switched from trophic to defensive functions