**Aleksandra Kvetkina 1,\*,**†**, Olesya Malyarenko 1,**†**, Aleksandra Pavlenko 1, Sergey Dyshlovoy 2,3,4, Gunhild von Amsberg 2,3, Svetlana Ermakova <sup>1</sup> and Elena Leychenko <sup>1</sup>**


Academic Editor: Luisa Tesoriere

Received: 3 November 2020; Accepted: 15 December 2020; Published: 17 December 2020

**Abstract:** Actinoporins are the most abundant group of sea anemone cytolytic toxins. Their membranolytic activity is of high interest for the development of novel anticancer drugs. However, to date the activity of actinoporins in malignant cells has been poorly studied. Here, we report on recombinant analog of Hct-S3 (rHct-S3), belonging to the combinatory library of *Heteractis crispa* actinoporins. rHct-S3 exhibited cytotoxic activity against breast MDA-MB-231 (IC50 = 7.3 μM), colorectal HT-29 (IC50 = 6.8 μM), and melanoma SK-MEL-28 (IC50 = 8.3 μM) cancer cells. The actinoporin effectively prevented epidermal growth factor -induced neoplastic transformation of JB6 Cl41 cells by 34% ± 0.2 and decreased colony formation of HT-29 cells by 47% ± 0.9, MDA-MB-231 cells by 37% ± 1.2, and SK-MEL-28 cells by 34% ± 3.6. Moreover, rHct-S3 decreased proliferation and suppressed migration of colorectal carcinoma cells by 31% ± 5.0 and 99% ± 6.4, respectively. The potent anti-migratory activity was proposed to mediate by decreased matrix metalloproteinases-2 and -9 expression. In addition, rHct-S3 induced programmed cell death by cleavage of caspase-3 and poly (ADP-ribose) polymerase, as well as regulation of Bax and Bcl-2. Our results indicate rHct-S3 to be a promising anticancer drug with a high anti-migratory potential.

**Keywords:** actinoporin; sea anemone; *Heteractis crispa*; anticancer activity; anti-migratory activity
