Fred Hutchison Cancer Research Institute, Seattle, WA, USA. pshannon@fhcrc.org|Fred Hutchison Cancer Research Institute, Seattle, WA, USA. pshannon@fhcrc.org|Fred Hutchison Cancer Research Institute, Seattle, WA, USA. pshannon@fhcrc.org|Fred Hutchison Cancer Research Institute, Seattle, WA, USA. pshannon@fhcrc.org|Fred Hutchison Cancer Research Institute, Seattle, WA, USA. pshannon@fhcrc.org