Abstract Resistance to chemotherapy agents is a major challenge
infront of cancer patient treatment and researchers. It is
known that several factors, such as multidrug resistance proteins
and ATP-binding cassette families, are cell membrane
transporters that can efflux several substrates such as chemotherapy
agents from the cell cytoplasm. To reduce the adverse
effects of chemotherapy agents, various targeted-based cancer
therapy (TBCT) agents have been developed. TBCT has revolutionized
cancer treatment, and several agents have shown
more specific effects on tumor cells than chemotherapies.
Small molecule inhibitors and monoclonal antibodies are specific
agents that mostly target tumor cells but have low side
effects on normal cells. Although these agents have been very
useful for cancer treatment, however, the presence of natural
and acquired resistance has blunted the advantages of targeted
therapies. Therefore, development of new options might be
necessary. A better understanding of tumor cell resistance
mechanisms to current treatment agents may provide an appropriate
platform for developing and improving new treatment
modalities. Therefore, in this review, different mechanisms
of tumor cell resistance to chemotherapy drugs and
current targeted therapies have been described