Calcium channel blocker treatment of tumor cells induces alterations in the cytoskeleton, mobility of the integrin αIIbβ3 and tumor-cell-induced platelet aggregation

Jozsef Timar, Hemi Chopra, X. Rong, James S. Hatfield, Suzanne E.G. Fligiel, James M. Onoda, John D. Taylor, Kenneth V. Honn

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21 Citations (Scopus)


Calcium channel blockers of the phenylalkylamine (i.e. verapamil), benzothiazepine (i.e. diltiazem) and dihydropyridine (i.e. nifedipine) classes were evaluated for effects on the tumor cell/platelet interactions using Walker 256 carcinosarcoma cells (W256 cells). When W256 cells were pretreated for 15 min with channel blockers at concentrations of 50-200 μM, macroscopic tumor-cell-induced platelet aggregation was inhibited (order of potency; nifedipine>diltiazem≫verapamil). However, ultrastructural analysis revealed limited, focal platelet aggregates associated with tumor cell plasma membranes of verapamil- and diltiazem-treated cells. There was no evidence of platelet activation or platelet association with the tumor cell membrane in cells pretreated with nifedipine. Walker 256 cells possess the integrin αIIbβ3. Tumor cell αIIbβ3 was shown to mediate tumor cell/platelet interactions in vitro [Chopra et al. (1988) Cancer Res. 48:3787]. Patching and capping of surface αIIbβ3 were inhibited by nifedipine>diltiazem≫verapamil. The degree of inhibition of αIIbβ3 receptor mobility parallels the inhibition of tumor-cell-induced platelet aggregation. W256 cells are characterized by a well-developed microfilament and intermediate filament network and by the absence of a distinct microtubular network. Calcium channel blockers had no effect on the low polymerization level of tubulin. However, they induced rearrangement of microfilament stress fibers. Intermediate filaments were also rearranged but to varying degrees. The order of effectiveness for alteration of intermediate filament organization was nifedipine>diltiazem while verapamil was ineffective. We propose that the previously reported inhibition of tumor cell/platelet interaction and tumor cell metastasis by calcium channel blockers [Honn et al. (1984) Clin Exp Metastasis 1:61] is due not only to the effects of the Ca2+ channel blockers on platelets, but also to their effect on the tumor cell cytoskeleton resulting in an inhibition of the mobility and function of the αIIbβ3 receptor.

Original languageEnglish
Pages (from-to)425-434
Number of pages10
JournalJournal of cancer research and clinical oncology
Issue number6
Publication statusPublished - Jun 1 1992


  • Cytoskeleton
  • Diltiazem
  • Nifedipine
  • Platelet aggregation
  • Verapamil
  • Walker 256 carcinosarcoma
  • αβ

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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