It could be the response is 'there's something dangerous in the environment, we got to move away', and so the response is for the cell to crawl in the opposite direction.

这个信号还有可能是,"外面很危险,我们得赶紧跑",于是细胞就向相反方向游走了

耶鲁公开课 - 生物医学工程探索课程节选