Multiple drug resistance in cancer revisited: the cancer stem cell hypothesis

Area of Science:

• Oncology
• Cancer Biology
• Stem Cell Research

Background:

• Current cancer therapies effectively treat bulk tumors but frequently fail to eradicate the root cause of relapse and metastasis.
• Tumor recurrence and metastasis are often attributed to a small population of cancer cells that evade treatment.
• Recent insights into tissue development and repair necessitate a re-evaluation of drug resistance mechanisms in cancer.

Purpose of the Study:

• To review the role of multiple drug resistance (MDR) transporters in cancer stem cells.
• To explore the implications of the cancer stem cell hypothesis for oncogenesis and tumor heterogeneity.
• To examine the efficacy of MDR reversal agents in enhancing cancer treatment.

Main Methods:

• Review of existing literature on MDR transporters in cancer and normal stem cells.
• Analysis of the cancer stem cell hypothesis.
• Evaluation of the therapeutic index of MDR reversal agents with antineoplastic agents.

Main Results:

• The cancer stem cell hypothesis posits that cancer-initiating cells are transformed stem cells with inherent self-protection mechanisms.
• Multiple drug resistance (MDR) transporters are active in both normal and cancer stem cells, conferring constitutive drug resistance.
• MDR transporters contribute to a low-frequency reservoir of drug-resistant cells within heterogeneous tumors.

Conclusions:

• The persistence of drug-resistant cancer stem cells is a key factor in treatment failure and disease recurrence.
• Targeting MDR transporters in cancer stem cells may offer a novel therapeutic strategy.
• Current MDR reversal agents have not proven effective in improving the therapeutic index of chemotherapy.