The strain-resistance transduction of commercially available In2O3/Au/Ag layered films supported by polyethylene terephthalate (PET) foil was studied. A colossal gauge factor as high as about 60,000 was observed upon a strain of 1%. Such ultra-high response is presumably owing to conductivity derived from the tunnelling current across cracks formed in the strained In2O3 film; the cracks - as visualized by scanning electron microscopy - are oriented perpendicularly to the strain vector and are noted for their uniform width across the sample. It is further demonstrated that the standardly defined gauge factor is incommensurate for strain sensors with transduction based on the tunnelling current and a redefined formula for the gauge factor was proposed. (C) 2016 Elsevier B.V. All rights reserved.