One group of researchers who worked with 17DMAG (a water-soluble inhibitor of the Hsp90 activity) proposed to designate ErbB3 as such a biomarker: they asserted that if ErbB3 is expressed by tumor cells, these cells cannot be sensitized to radiation by means of Hsp90 inactivation [9,17]. Here, ERBB3 is linked to neoplasm.