EGFR-binding peptide

1. A 12 to 18 amino acid peptide comprising the amino acid sequence represented by at least formula (1), (2), or (3):

X 1 -His-X 2 -X 3 -Asp-X 4 -X 5 -X 6 -X 7 -X 8 -Trp-His (1) (SEQ ID NO:55)

wherein X 1 is Trp or Phe;

X 2 is Leu, Met, or Ile;

X 3 is Ser, Ala, Thr, Gly, or Asn;

X 4 is Leu, Met, Ile, Val, or Ala;

X 5 is Trp, Phe, or Tyr;

X 6 is Gin, Asn, or Ala;

X 7 is Asn, Gln, or Ala; and

X 8 is Ala;

Phe-His-Asp-Trp-X 11 -Pro-X 12 -X 13 -X 14 -X 15 -X 16 -X 17 (2) (SEQ ID NO:56)

wherein X 11 is Leu or Ala;

X 12 is Glu or Ala;

X 13 is Val, Ala, Leu, or Ile;

X 14 is Ser or Ala;

X 15 is Pro or Ala;

X 16 is Pro, Val, Ile, or Ala; and

X 17 is Asp or Ala; and

Leu-His-X 21 -Ser-X 22 -Trp-Met-X 23 -X 24 -X 25 -X 26 -X 27 (3) (SEQ ID NO:57)

wherein X 21 is Gin or Ala;

X 22 is Glu or Ala;

X 23 is Tyr, Phe, Trp, His, or Ala;

X 24 is Val, Ala, Leu, or lie;

X 25 is Asp or Ala;

X 26 is Ile, Val, Leu, Met, or Ala; and

X 27 is His, Tyr, Phe, Lys, Arg, or Ala.

2. The peptide according to claim 1 , wherein in the formula (1), X 1 is Trp or Phe, X 2 is Leu, Met, or Ile, X 3 is Ser or Ala, X 4 is Leu or Ala, X 5 is Trp, Phe, or Tyr, X 6 is Gln or Ala, X 7 is Asn or Ala, and X 8 is Ala.

3. The peptide according to claim 1 , wherein, in formula (1), X 1 is Trp, X 2 is Leu or Met, X 3 is Ser or Ala, X 4 is Leu or Ala, X 5 is Trp, X 6 is Gln or Ala, X 7 is Asn or Ala, and X 8 is Ala.

4. The peptide according to claim 1 , wherein, in formula (2), X 11 is Leu or Ala, X 12 is Glu or Ala, X 13 is Val or Ala, X 14 is Ser or Ala, X 15 is Pro or Ala, X 16 is Pro or Ala, and X 17 is Asp or Ala.

5. The peptide according to claim 1 , wherein, in formula (2), X 11 is Leu, X 12 is Glu, X 13 is Val or Ala, X 14 is Ser, X 15 is Pro, X 16 is Pro or Ala, and X 17 is Asp.

6. The peptide according to claim 1 , wherein, in formula (3), X 21 is Gln or Ala, X 22 is Glu or Ala, X 23 is Tyr or Ala, X 24 is Val or Ala, X 25 is Asp or Ala, X 26 is Ile or Ala, and X 27 is His or Ala.

7. The peptide according to claim 1 , wherein, in formula (3), X 21 is Gln, X 22 is Glu, X 23 is Tyr or Ala, X 24 is Val or Ala, X 25 is Asp, X 26 is Ile or Ala, and X 27 is His or Ala.

8. The peptide according to claim 1 , having epidermal growth factor receptor (EGFR) binding properties.

9. A pharmaceutical agent comprising the peptide according to claim 1 or a labeled product thereof.

10. A detection agent for a cancer cell or a cancer tissue comprising the peptide according to claim 1 or a labeled product thereof.