Hematopoietic toxicity and cell cycle perturbations induced by new DNA minor groove-alkylating agents

Chb-M', an Inhibitor of the RUNX Family Binding to DNA, Induces Apoptosis in p53-Mutated Non-Small Cell Lung Cancer and Inhibits Tumor Growth and Repopulation In Vivo

Runt-related transcription factor (RUNX) proteins are considered to play various roles in cancer. Here, we evaluated the anticancer activity of Chb-M', a compound that specifically and covalently binds to the consensus sequence for RUNX family proteins, in p53-mutated non-small cell lung cancer cells. Chb-M' killed the cancer cells by inducing apoptosis. The compound showed an anticancer effect comparable to that of the clinically used drugs alectinib and ceritinib in vivo. Notably, Chb-M' extended the cancer-free survival of mice after ending treatment more effectively than did the other two drugs. The results presented here suggest that Chb-M' is an attractive candidate as an anticancer drug applicable to the treatment of non-small cell lung cancer and various other types of cancers.

A flow cytometric journey into cell cycle analysis

Cell cycle involves a series of changes that lead to cell growth and division. Cell cycle analysis is crucial to understand cellular responses to changing environmental conditions. Since its inception, flow cytometry has been particularly useful for cell cycle analysis at single cell level due to its speed and precision. Previously, flow cytometric cell cycle analysis relied solely on the measurement of cellular DNA content. Later, methods were developed for multiparametric analysis. This review explains the journey of flow cytometry to understand different molecular and cellular events underlying cell cycle using various protocols. Recent advances in the field that overcome the shortcomings of traditional flow cytometry and expand its scope for cell cycle studies are also discussed.

Chromatin structure determines accessibility of a hairpin polyamide-chlorambucil conjugate at histone H4 genes in pancreatic cancer cells

We have shown that a specific pyrrole-imidazole polyamide-DNA alkylator (chlorambucil) conjugate, 1R-Chl, alters the growth characteristics of various cancer cell lines in culture, and causes these cells to arrest in the G2/M stage of the cell cycle, without apparent cytotoxicity. This molecule has also shown efficacy in several mouse xenograft models, preventing tumor growth. Previous microarray studies have suggested that members of the histone H4 gene family, H4c and H4j/k, are the primary targets of this molecule, leading to reduced histone mRNA synthesis and growth arrest in cancer cells. In the present study, we examine the effects of 1R-Chl on transcription of other members of the H4 gene family, with the result that mRNA transcription of most genomic copies of H4 are down-regulated by 1R-Chl in a human pancreatic cancer cell line (MIA PaCa-2), but not in a cell line of non-cancerous origin (HEK293 cells). The basis for this differential effect is likely an open chromatin conformation within the H4 genes in cancer cells. Chromatin immunoprecipitation experiments show increased histone acetylation on the histone H4 genes in cancer cells, compared to HEK293 cells, explaining the differential activity of this molecule in cancer versus non-cancer cells.

Small molecules targeting histone H4 as potential therapeutics for chronic myelogenous leukemia

We recently identified a polyamide-chlorambucil conjugate, 1R-Chl, which alkylates and down-regulates transcription of the human histone H4c gene and inhibits the growth of several cancer cell lines in vitro and in a murine SW620 xenograft model, without apparent animal toxicity. In this study, we analyzed the effects of 1R-Chl in the chronic myelogenous leukemia cell line K562 and identified another polyamide conjugate, 6R-Chl, which targets H4 genes and elicits a similar cellular response. Other polyamide conjugates that do not target the H4 gene do not elicit this response. In a murine model, both 1R-Chl and 6R-Chl were found to be highly effective in blocking K562 xenograft growth with high-dose tolerance. Unlike conventional and distamycin-based alkylators, little or no cytotoxicities and animal toxicities were observed in mg/kg dosage ranges. These results suggest that these polyamide alkylators may be a viable treatment alternative for chronic myelogenous leukemia.

Potentiation of antitumor immunity by antibody-directed enzyme prodrug therapy

Antibody-directed enzyme prodrug therapy (ADEPT) has displayed antitumor activity in animal models and clinical trials. We examined whether antitumor immunity is generated during ADEPT by employing an immunoenzyme composed of the monoclonal antibody (MAb) RH1 conjugated to beta-glucuronidase to target rat AS-30D hepatocellular carcinoma tumors. A glucuronide prodrug of p-hydroxyaniline mustard was used to treat malignant ascites after immunoenzyme localization at the cancer cells. ADEPT cured more than 96% of Sprague-Dawley rats bearing advanced malignant ascites, and all cured rats were protected from a lethal challenge of AS-30D cells. Immunization with radiation-killed AS-30D cells or AS-30D cells coated with immunoenzyme did not provide tumor protection. Likewise, ex vivo treatment of tumor cells by ADEPT before injection into rats did not protect against a tumor challenge. AS-30D and N1-S1 hepatocellular carcinoma cells but not unrelated syngeneic tumor cells were lysed by peritoneal exudate cells isolated from ADEPT-cured rats. Depletion of CD8(+) but not CD4(+) T cells or natural killer (NK) cells reduced the cytolytic activity of peritoneal lymphocytes. ADEPT did not cure tumor-bearing rats depleted of CD4(+) and CD8(+) T cells even though it was curative when given 7 days after tumor transplantation in rats with an intact immune system, indicating that ADEPT can synergize with host immunity to increase therapeutic efficacy. These results have important implications for the clinical application of ADEPT.