Resistance to anticancer agents by tumor cell populations presents a major barrier to successful cancer chemotherapy today. In vitro exposure of tumor cell populations to cytotoxic natural products such as vinca alkaloids generally elicits the emergence of a multidrug resistance (MDR) phenotype. MDR is defined as resistance against the cytotoxic agent to which cells have been exposed and cross-resistance against diverse cytotoxic agents, many of which are anticancer drugs. The most consistent change detected in MDR cells in vitro is overexpression of P-glycoprotein, a membrane-spanning protein believed to pump anticancer drugs out of cells. The tumor promoter receptor protein kinase C (PKC) is also implicated in MDR. Specific PKC activators, such as 12-0-tetradecanoylphorbol-13-acetate (TPA), can confer a phenotype resembling MDR on drug-sensitive cells, and several PKC inhibitors can partially reverse MDR in vitro. TPA also induces P-glycoprotein phosphorylation, suggesting that PKC may regulate P- glycoprotein function in MDR cells. A direct correlation has been observed between the level of PKC activity and MDR in cultured murine fibrosarcoma UV-2237M cells, suggesting the usefulness of UV-2237M cells in studies aimed at defining the role of PKC in MDR. The proposed studies will establish the basis for elevated PK activity in MDR UV-2237M cells, since it may provide a modus operandi for reversing MDR. The proposed studies will also determine whether PKC activation regulates P-glycoprotein function, by measuring the effects of PKC catalysis on the drug-binding and ATPase activities of P-glycoprotein. Since PKC activation leads to numerous changes in gene expression, its effects on P-glycoprotein expression will be determined. Little is known regarding the role of P-glycoprotein in drug resistance in vivo. In vivo resistance mechanisms may involve environmental factors, intrinsic properties of MDR tumor cells, or both. In the proposed studies, drug-resistant tumors and metastases will be generated using UV-2237M cell lines in syngeneic mice to determine whether P-glycoprotein or PKC expression correlates with drug resistance in tumors and metastatic nodules located in various organ environments in vivo.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29CA052460-04
Application #
3459900
Study Section
Experimental Therapeutics Subcommittee 1 (ET)
Project Start
1990-07-01
Project End
1995-06-30
Budget Start
1993-07-01
Budget End
1994-06-30
Support Year
4
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Texas MD Anderson Cancer Center
Department
Type
Other Domestic Higher Education
DUNS #
001910777
City
Houston
State
TX
Country
United States
Zip Code
77030