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Mizejewski. J Cancer Metastasis Treat 2019;5:35 I http://dx.doi.org/10.20517/2394-4722.2018.70 Page 9 of 11

some instances, the derived peptide displayed an opposite action from its host protein such as angiogenic
inhibition versus enhancement of new blood vessel growth. In another type of protein-derived peptide, the
amino acid segment is not cleaved from the preproprotein, but rather exposed following a conformational
change of the tertiary folded polypeptide. As an example, metabolic stresses of excessive ligand
concentrations can temporarily convert the growth enhancing AFP molecule into a growth inhibitory
protein. The transitory AFP molecule then refolds back to its tertiary form, and full length AFP once again
displays the property of growth enhancement.

In the future, it might be feasible to administer short peptides to metastatic patients by injection, infusion,
and osmotic pumps, or via sublingual routes to patients in early and/or late metastatic disease. Such peptides
are also capable of down-regulating the expression of metastasis-associated proteins as previously described
[44]
for GIP . Peptides are short half-life molecules with good targeting properties, and adequate target binding
[43]
(loading/off- loading) affinities . Natural or synthesized peptides might potentially serve as treatment
adducts in combination with next generation therapeutic cancer drugs. Peptide binding, occupation, down-
regulation, and saturation of ECM proteins in the interstitium may possibly serve to disable and sever the
primary tumor and/or metastatic nesting sites from their ECM communication networks.

DECLARATIONS
Acknowledgments
The author extends his gratitude and thankfulness to Ms. Jennifer Wright in the typing and processing of
this manuscript.

Authors’ contributions
Mizejewski GJ solely contributed to the article.

Availability of data and materials
Not applicable.

Financial support and sponsorship
None.

Conflicts of interest
All authors declared that there are no conflicts of interest.

Ethical approval and consent to participate
Not applicable.

Consent for publication
Not applicable.

Copyright
© The Author(s) 2019.

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