Restoring a telomere dependent Hayflick limit to treat hematological malignancies

Background: The consequence of continued cell proliferation of tumor cells despite their critically short telomeres allows for ongoing genomic instability and its propagation to the next generation of cells. Genomic instability is an enabling hallmark of cancer . In stark contrast to normal cells, tumor cells escape the Hayflick limit of lineage-dependent limited life span through the activation of telomere maintenance pathways. These pathways allow cells to continue dividing, bypassing the Hayflick limit. Two telomere maintenance pathways are used by cancer cells to maintain telomere length. Telomerase activation is the most common pathway and is used by 85% of all tumor cells, while alternative lengthening of telomere (ALT) is used by the remainder. Some tumors, albeit rare, show the co-activation of both pathways. Methods: We use in our study multiple hematological cancer cell lines including :RPMI8226, MM.1R-CRL-2975 (Multiple Myeloma), MDS-L, MDS-92 (Myelodysplastic syndromes), OCI-AML3, Jurkat (Acute Leukemia), and human primary fibroblasts (GL 51/92 Roe). The inhibitions used BIBR1532 (72 hours) to inhibit the telomerase pathway and Trabectedin(72-144hours) to inhibit the ALT pathway. Cell death was assayed by live cell imaging using NucGreen™Dead488 and trypan blue exclusion. Results: Consecutive inhibition of both telomere maintenance pathways shows a significant decrease of cell viability rate over 72h of treatment with BIBR1532 in all hematological cancer cell lines. Cell death is increased by adding Trabectedin for an additional 3 days period and reaches 90 % in cancer cells. In contrast, the normal primary fibroblasts (GL51/92 Roe) at low and high passages do not show cell death. Conclusion: The sequential inhibition of both telomere maintenance pathways using small molecules in multiples hematological cancer cell lines demonstrates a decrease in cell viability while primary fibroblasts show no significant effects on survival. Future studies using primary cancer cells are expected to confirm these results and to pave the way for cancer treatment options in hematological. Keywords: neoplasia; genome instability; telomerase; alternative of lengthening telomere (ALT); cell lines; myelodysplastic syndromes (MDS); acute leukemia (AL); multiple myeloma; small molecules