Abstract: This document provides methods and materials involved in identifying and treating mammals having a cancer (e.g., a clear cell renal cell carcinoma (ccRCC)) based, at least in part on, 5-hydroxymethylcytosine (5hmC) levels. For example, methods and materials for administering a high dose of ascorbic acid (AA) with or without an additional chemotherapeutic agent to a mammal identified as having cancer having a reduced level of 5hmC are provided. Methods and materials for administering a chemotherapeutic agent without administering a high dose of AA to a mammal identified as having cancer exhibiting 5hmC expression also are provided.