The VHL gene is found in a region of the genome commonly deleted in lung cancer; there has been speculation that although the remaining VHL gene is still intact, gene dosage effects could still cause it to play a causative role. For this to be true, VHL
a. Must have feedback regulation of its own protein levels.
b. Must have similar genes in the genome which make its deletion redundant
c. Must experience a halving of protein levels when one copy of the gene is gone
d. Must act to induce HIF-1 increases that regulate VHL transcription
e. Must influence apoptosis