▁are ▁also ▁reliable ▁markers . ▁The ▁most ▁frequently ▁encountered ▁products ▁in ▁ne uro end ocr ine ▁tum or ▁cells ▁across ▁pro state ▁cancer ▁samples ▁appear ▁to ▁be ▁cal cit on in ▁( in ▁more ▁than ▁one ▁third ▁of ▁cases ), ▁ne uro t ens in , ▁ser ot on in , ▁human ▁ch or ionic ▁g on ad otrop in , ▁v aso active ▁int est inal ▁pe pt ide ▁( V IP ) ▁and ▁bomb es in / g astr in - re le asing ▁pe pt ide . ▁Ne uro end ocr ine ▁tum or ▁cells ▁express ▁cy to ker at ins ▁that ▁are ▁typically ▁expressed ▁by ▁lum inal ▁secret ory ▁type ▁cells , ▁but ▁lack ▁bas al ▁cell ▁markers ▁such ▁as ▁high ▁mole cular ▁weight ▁cy to ker atin ▁and ▁p 6 3 . ▁They ▁are ▁negative ▁for ▁and ro gen ▁re ceptor ▁and ▁pro state - specific ▁ant igen ▁( PS A ) ▁and ▁are ▁positive ▁for ▁pro state ▁acid ▁ph osph at ase . ▁Ne uro end ocr ine ▁tum or ▁cells ▁are ▁also ▁negative ▁for ▁the ▁pro l ifer ation ▁marker ▁Ki - 6 7 ; ▁however , ▁adjacent ▁non - ne uro end ocr ine ▁tum or ▁cells ▁appear ▁to ▁display ▁an ▁increased ▁expression ▁of ▁Ki - 6 7 . ▁As ▁opposed ▁to ▁their ▁normal ▁ne uro end ocr ine ▁counter parts , ▁tum or ▁ne uro end ocr ine ▁cells ▁express ▁the ▁beta - ox id ative ▁en zym e ▁alpha - m eth y