Pancreatic ductal adenocarcinoma (PDAC) is associated with high mortality and therapy resistance. Here, we show that low expression of κB-Ras GTPases is frequently detected in PDAC and correlates with higher histologic grade. In a model of KRas G12D-driven PDAC, loss of κB-Ras accelerates tumour development and shortens median survival. κB-Ras deficiency promotes acinar-to-ductal metaplasia (ADM) during tumour initiation as well as tumour progression through intrinsic effects on proliferation and invasion. κB-Ras proteins are also required for acinar regeneration after pancreatitis, demonstrating a general role in control of plasticity. Molecularly, upregulation of Ral GTPase activity and Sox9 expression underlies the observed phenotypes, identifying a previously unrecognized function of Ral signalling in ADM. Our results provide evidence for a tumour suppressive role of κB-Ras proteins and highlight low κB-Ras levels and consequent loss of Ral control as risk factors, thus emphasizing the necessity for therapeutic options that allow interference with Ral-driven signalling.

A three-axis solar sail attitude control system for interplanetary missions is proposed: required steering is achieved by means of a small control mass in the solar sail plane, whereas roll-axis control is achieved through the rotation of ballast with two masses at the extremities. The satellite is fixed at the sail geometrical centre: this solution avoids the difficulties arising from the employment of an out-of-plane control boom with the satellite at the end, i.e. pointing problems for optical payloads and communication antennas. A circular sailcraft of 220 kg with characteristic acceleration a(c) = 0.5 mm/s(2) is considered, and the control system performances are presented in terms of pointing accuracy for a rendezvous mission to Mercury. The dynamical model takes into account the perturbation torque because of an offset between the centre of pressure and the geometrical sail centre, as well as the Sun gravity-gradient effect and a perturbation torque on the roll axis

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