Podium Presentations

PRP-1, cytokine neuropeptide manifested itself as a strong antiproliferative peptide (Galoian at al., Neurochem Res., 2009 and 2011; Galoian at al., Tumour Biol. and Neurochem Res., 2011) inhibited mTOR serine/threonine-protein kinase (mTORC-1) (Galoian et al., Neurochem. Res. 2011). Also, PRP-1 treatment showed 80% inhibition in breast carcinoma cell line, MDA 231 estrogen negative breast cancer cell line (Galoian et al., Tumour Biol. 2011). Our laboratory was the first to demonstrate the presence of innate immune toll-like receptors (TRL) on the surface of chondrosarcoma cells, moreover, PRP-1 is a ligand for TLR-1,2 and TLR-6 (Galoian et al., Int J Oncol., 2018).

The CSC theory states that tumor growth is similarly triggered by small numbers of tumor stem cells. This population is responsible for the inevitable recurrence of tumors after initially successful chemotherapy and/or radiation therapy CSCs, sometimes called tumor-initiating cells are responsible for the phenomenon of tumor dormancy, and metastasis.

In sorted by flow cytometry cell fractions, the PRP-1 inhibited the expression of ALDH1, the only stem cell marker for chondrosarcoma. The western blot experiments confirmed the results. The elimination of the CSCs population corresponding to the ALDH1high pool was observed when treated with PRP-1 (Moran et al., Oncology Reports, 2020).

This data led us to the isolation of 3D spheroids from human chondrosarcoma cells which correspond to the CSCs model. Using colony formation and spheroid assays, we observed PRP-1 to target the specific CSC population in a powerful inhibitory dose-response manner (Granger et al., Molecular Medicine Reports, 2020).

This study won first place in the SAMA Grand Rounds competition organized by the Orthopaedic Surgery Department, Miller School of Medicine of the University of Miami. The presentation was accepted by the American Academy of Orthopedic Surgery Congress for the podium presentation in 2020.

CSCs have powerful tumorigenesis ability, self-renewal capacity, as well as chemotherapy and radiotherapy resistance. CSCs may be a critical driving force for several types of cancer. Selectively targeting CSCs with various agents may be a novel and promising therapeutic strategy against cancer.

Our future goals include creating bone and soft tissue sarcoma xenograft mice models to study the ability of PRP-1 and its analogs to shrink and destroy the primary tumor as a subsequent metastatic spread. Unlike many conventional chemotherapy drugs which do not target CSCs we expect that PRP-1 will be able to eradicate CSCs and prevent disease relapse. Moreover, PRP-1 (being a natural brain neuropeptide) does not affect normal benign cells, while inhibiting malignant ones (Galoian et al., Neurochem Res, 2009) guaranteeing less toxicity associated with conventional chemotherapy side effects.

Cancer can lead to the accumulation of toxic unfolded proteins resulting in excessive cellular cargo that alters endoplasmic reticulum (ER) functioning, a state known as ER stress. The cell responds to ER stress through a process known as “unfolded protein response” (UPR). Depending on cellular context UPR can be pro or anti oncogenic. In chondrosarcoma, UPR protein machinery is suppressed, (Galoian et al., Oncology Reports submitted, 2022) thus manifesting tumor-suppressive properties. The treatment with PRP-1 showed upregulation of UPR proteins such as IRE1α, PERK, ATF6, ATF4, EIF2α, XBP-1, and CHOP on both protein and mRNA levels (Galoian et al., Oncology Reports submitted, 2022).

We hypothesize that PRP-1 leads to activation of the PERK-eIF2α-ATF4-CHOP, which in turn activates IRE1α -XBP1, ATF6 branch. This is the first indication that innate receptors ligand PRP-1 can regulate the branches of the UPR. Since the activation of the PERK- eIF2α -ATF4-CHOP and IRE1α -XBP1 branches we have observed in ALDH^high and in spheroids corresponding fractions to cancer stem cells, we assume that this activation has an important role in the ability of PRP-1 drastically decrease the CSC. Our future efforts will be directed to understanding the link between UPR pathways, TLR signaling, and its epigenetic regulation which leads to CSC targeting with PRP-1 treatment.

Downregulation of oncogenes and upregulation of tumor suppressors was reported by our group (Galoian et al., Neurochem. Res., 2009 and (Galoian et al., Int. J Oncol. 2015).

Upregulation of desmosomal proteins is attributed to PRP-1 ability to upregulate most of the tumor suppressors in human chondrosarcoma (Galoian et al., Mol Clin Oncol. 2015), depending on the molecular pathway they represent, for example, it did not inhibit Hedgehog signaling pathway tumor suppressors (Galoian et al., Mol Clin Oncol. 2016).

On the epigenetic level, PRP-1 was able to down-regulate onco (miR509-3p, miR589, miR490-3p, and miR 550) and up-regulate tumor suppressor miRNAs (miR20a, miR125b, and miR192) (Galoian et al., Tumour Biol. 2014). Also, the treatment with PRP-1 reduced the expression of the miR302-367, which targets the embryonic stem cell marker Nanog and Bmi-1 (Galoian et al., Int. J Oncol. 2015)

The H3K9-specific histone demethylase is an enzyme that represses tumor suppressor genes and contributes to cancer progression. PRP-1 also showed the ability to inhibit H3K9 (Galoian et al., Mol Clin Oncol. 2015). Moreover, PRP-1 is shown to be an inhibitor of SWI/SNF(BAF) chromatin remodeling complexes (Moran et. al., Oncol Rep. 2020).