Class I MHC-Restricted T Cell Responses to Tumors Can Be

Class I MHC-restricted T cell responses to tumors can be demonstrated in patients with various types of tumors, yet most of these tumors do not express costimulatory molecules. Which mechanism most likely explains how naive CD8⁺ T cells specific for antigens expressed by these tumors are stimulated to differentiate into cytolytic T lymphocytes?

A) Malignant transformation of CD8⁺ T cells
B) Tumor secretion of T cell-activating cytokines
C) Cross reaction of microbe-specific CD8⁺ T cells with tumor antigens
D) Cross priming
E) Antigenic modulation