SPAG9 and prostate carcinoma: Moreover, changes in expression of components of the microtubule vesicular trafficking system, which control the switch between anterograde and retrograde transport, such as increased ARF6 and JIP4 (encoded by SPAG9), have been reported to support the proliferation and invasion of prostate cancer cells, possibly by promoting endosome anterograde transport, which supports the release of proteolytic factors like PSA [34,35,37,38].