One method of drug resistance involves which mechanism?

One prominent mechanism of drug resistance in cancer cells is the increased removal of the drug from the cell. This often occurs through the upregulation of efflux pumps that transport the drug out of the cell more efficiently than it can enter or remain, reducing the drug's efficacy. These pumps recognize various chemotherapeutic agents and actively eliminate them, thereby allowing cancer cells to survive in the presence of drugs that would typically be cytotoxic. This mechanism can significantly limit the effectiveness of the treatment, leading to treatment failures and cancer progression.

The other options, while they describe processes that may occur in cancer biology, do not directly relate to the established mechanisms of drug resistance in the same way. Increased drug uptake by cancer cells, for example, would enhance sensitivity to chemotherapy rather than contribute to resistance. Alterations to the metabolism of healthy cells may affect the overall environment but do not represent a direct drug resistance mechanism. Lastly, the development of beneficial functions in tumor cells may describe adaptive traits of cancer but, again, is not a mechanism by which drugs are effectively resisted.