Induction of apoptosis, anti-proliferation, tumor-angiogenic suppression and down-regulation of Dalton's Ascitic Lymphoma (DAL) induced tumorigenesis by poly-l-lysine: A mechanistic study

Purpose: The present study, attempts to validate the molecular mechanism(s) of Poly-l-lysine (PLL) induced Apoptosis, anti-proliferative and anti-tumorigenic properties in in-vitro HUVECs cells and Dalton's Ascitic Lymphoma (DAL) and in in-vivo DAL cell bearing BALB/c mice model.

Materials and methods: The cell proliferation assay and morphological assay was carried out using the MTT assay and Giemsa staining method. The antitumor activity of PLL was evaluated in BALB/c mice at 20 and 40 mg/kg/b.w doses for 21 days for DAL solid tumor model. Several tumor evaluation endpoints, hematological and biochemical parameters were estimated. Additionally, the tumor Apoptosis, anti-proliferative and anti-tumor angiogenesis effects were assessed using western blots and immunohistochemistry.

Results: PLL significantly decreased cell proliferation in in-vitro HUVECs and DAL cells without significant effects on normal cell growth. PLL also induced alteration in cellular morphology in DAL cells. Therafter, in the BALB/c mouse model, PLL had noticeable inhibition in DAL-induced tumorigenesis. This inhibition was evident through reduced solid tumor volume and weight versus the control group. However, PLL promoted tumor Apoptosis and suppressed cell-proliferation and tumor-angiogenesis. PLL also increased hematological markers significantly compared to 5-flurouracil (5-FU). The amount of TdT in the nuclei of DAL cells in mice treated with PLL was significantly increased while in contrast decreases of anti-apoptotic protein Bcl-2 expression were observed. PLL also significantly upregulated the pro-apoptotic protein Bax and activated Caspase-3. Measurable decreases of cyclin-D₁ were observed through PLL treatments, an indicator of cell-cycle arrest. These studies also indicate PLL's induction and anti-proliferative effects through suppression of the c-Myc and Ki-67 proliferation-indices. Additionally, PLL inhibited tumor-angiogenesis through suppression of VEGF and CD34 protein expression levels and reduction ofmicrovesseldensityversus similar parameters in tumors from control mice.

Conclusion: The present study offers opportunities and hopes for possible anti-tumortherapies with PLL in the near future and warrants further formulation developments.