Reducing capacitance of a wire
I'm not 100% sure I understand your needs, but you might consider a negative capacitance amplifier, as in http://en.wikipedia.org/wiki/Negative_impedance_converter, whose parallel negative input impedance should subtract that of your wire.  This is a positive feedback trick, so if your negative capacitance is too high, your system will go unstable.

This is used all the time in neuroscience to deal with large capacitances in glass microelectrodes, but I've never seen it used for cable capacitance.