Cell lines A and B both survive in tissue culture containing serum but do not proliferate.Factor F is known to stimulate proliferation in cell line A.Cell line A produces a receptor protein (R) that cell line B does not produce.To test the role of receptor R, you introduce this receptor protein into cell line B, using recombinant DNA techniques.You then test all of your various cell lines in the presence of serum for their response to factor F, with the results summarized in Table 16-9. $\begin{array} { l l l } \text { Cell line } & \text { Factor } F & \text { Response } \\\hline \text { A } & \text { - Factor F } & \text { Cells do not proliferate } \\\text { A } & \text { + Factor F } & \text { Cells proliferate } \\\text { B } & \text { - Factor F } & \text { Cells do not proliferate } \\\text { B } & \text { + Factor F } & \text { Cells do not proliferate } \\\text { B + receptor R } & \text { - Factor } F & \text { Cells proliferate } \\\text { B + receptor R } & \text { + Factor F } & \text { Cells proliferate }\end{array}$ Table 16-9
Which of the following cannot be concluded from your results above?