Main Research Findings

1) Treatment with Goralatide has the potential to enhance the selectivity of hyperthermic purging in human progenitor cells.

2) Bone marrow stem cells and progenitors experience increased protection from Doxorubicin-induced toxicity following administration of Goralatide.

 

Selected Data

1) The research team of Wierenga et al examined the effects of negative regulator Goralatide on the proliferative activity and heat sensitivity of committed granulocyte–macrophage progenitors, as well as late and early erythroid progenitor cells. The study involved the collection and preparation of bone marrow cells from patients in complete remission and bone marrow transplant donors. Informed consent was obtained from all participants for research purposes. Mononuclear cells were isolated using Ficoll-Paque Plus and subsequently resuspended in RPMI-1640 medium. The cell suspensions were then dispersed through a 21-gauge needle to ensure even distribution, and nucleated cells were counted using a hemocytometer [1].

Additionally, bone marrow cells were obtained from five patients diagnosed with acute myeloid leukemia based on the French-American-British classification criteria. These cells were sourced from the St. Jude Children’s Research Hospital bone marrow cell bank. Four of the acute myeloid leukemia cases were categorized as M2, while one case was classified as M4. The cells were thawed rapidly at 37°C, washed twice with RPMI-1640 medium, and counted to ensure accurate quantification. The viability of the cells was consistently above 95%, ensuring that the experimental results were reliable and based on healthy, functional cells.

Goralatide was initially dissolved in RPMI-1640 medium to prepare a stock solution with a concentration of 10⁻⁷ M. Both normal bone marrow cells and acute myeloid leukemia cells were cultured at a concentration of 2 × 10⁶ cells per milliliter in designated culture flasks. These cells were incubated for 21 hours in the presence of 10⁻⁹ M Goralatide in RPMI-1640 medium, which had been supplemented with 10% fetal calf serum to enhance cellular growth. To prevent the degradation of Goralatide by serum enzymes, captopril was added at a concentration of 1 mM. After incubation, the cells were washed twice to remove any residual substances and were immediately subjected to heat treatment for further analysis [1].

The study employed the hydroxyurea-kill assay to assess the proliferative activity of both leukemic and hematopoietic progenitor cells. In this procedure, hydroxyurea at a concentration of 200 mg/ml was added to cell suspensions both with and without Goralatide treatment. These suspensions were incubated at 37°C for 60 minutes, either immediately after adding hydroxyurea or after a 20-hour incubation period. Following the incubation, the cells were washed thoroughly and plated for colony-forming assays, allowing for the determination of their proliferative capacity.
For hyperthermic treatments, cell suspensions were prepared at a density of 2–3 × 10⁶ cells/ml in RPMI-1640 medium with or without 10% FCS. These treatments were carried out at a controlled temperature of 43 ± 0.1°C for up to 120 minutes. The heat exposure was then halted by immediate cooling. The treated cells were subsequently diluted to appropriate concentrations and immediately used for colony-forming assays to assess the effects of hyperthermia on cell viability and proliferation [1].

Both normal bone marrow cells and acute myeloid leukemia cells were plated in duplicate in methylcellulose medium for colony-forming assays. The plating concentrations varied from 5 × 10⁴ to 5 × 10⁶ nucleated cells per milliliter. In this system, colony growth was stimulated through the addition of agar leukocyte-conditioned medium and erythropoietin. The cultures were maintained in 35-mm polystyrene culture dishes at 37°C within a humidified atmosphere containing 5% CO₂ to mimic physiological conditions [1].
In the cultures containing normal or remission bone marrow, colonies were evaluated at different time points based on their size and composition. Colonies containing more than 20 hemoglobinized cells were classified as colony-forming unit-erythroid (CFU-E) on day 8 of culture. By day 14, larger colonies with more than 50 hemoglobinized cells were identified as burst-forming unit-erythroid (BFU-E), while colonies without hemoglobinized cells were categorized as colony-forming unit-granulocyte macrophage (CFU-GM).

For leukemic bone marrow samples, blast colonies were assessed after 14 days in culture. A colony was defined as a blast colony if it contained more than 20 cells. These colony-forming assays provided valuable insights into the growth patterns of both normal and leukemic cells under different experimental conditions, helping to evaluate the effects of Goralatide and hyperthermia on hematopoietic and leukemic cell populations [1].

Overall, this study employed a rigorous methodology to analyze the impact of Goralatide, hydroxyurea treatment, and hyperthermia on both normal and leukemic bone marrow cells. The careful preparation of bone marrow samples, controlled incubation conditions, and detailed colony-forming assays ensured that the results provided meaningful insights into hematopoietic cell proliferation and leukemia treatment strategies [1].

2) The study performed by the research team of Massé et al investigated the effects of AcSDKP on hematologic toxicity and bone marrow recovery following doxorubicin (DOX) treatment in BALB/c mice. The mice, aged 8 to 12 weeks, were housed under specific pathogen-free conditions in accordance with French regulations. The drugs used included DOX, synthetic AcSDKP, and recombinant G-CSF.

For in vivo treatments, AcSDKP was administered subcutaneously either as a single injection or through continuous infusion. The treatment was given 24 or 48 hours before DOX administration. Several schedules of AcSDKP injections were tested: a single injection 48 hours prior to DOX, three injections at 48 hours, 24 hours, and 1 hour before DOX, six injections administered twice daily starting 48 hours before DOX, or nine injections administered three times daily starting 48 hours before DOX. Additionally, the six-injection protocol was used to evaluate a dose-response effect with total doses ranging from 0.072 to 720 μg/mouse. For continuous infusion, 7.2 μg of AcSDKP was delivered over three days via minipumps implanted 24 or 48 hours before DOX treatment. Control mice received saline either by subcutaneous injection or minipump [2].

DOX was administered intraperitoneally using a three-injection protocol: two injections on day 1 at 10:00 AM and 5:00 PM and one injection on day 2 at 10:00 AM at a dose of 2.65 mg/kg per injection, totaling 7.95 mg/kg. G-CSF was injected IP at doses of 100, 300, or 500 ng (equivalent to 5, 15, or 25 μg/kg) once daily from day 3 to day 6 following DOX treatment. For survival experiments, mice were divided into groups of 30 and received either AcSDKP or saline, administered by subcutaneous injection or continuous infusion. DOX treatment followed the same protocol across all groups, and mortality was recorded daily [2].

Hematologic toxicity was evaluated by monitoring the recovery of three different hematopoietic cell populations after DOX treatment. Two protocols were used: one where AcSDKP was administered alone either by injection or continuous infusion before DOX, and another where six subcutaneous injections of AcSDKP were administered starting 48 hours before DOX, followed by G-CSF treatment from day 3 to day 6 post-DOX. Four to five mice per group were sacrificed on days 3, 4, 7, 11, 14, and 18, and bone marrow cells from tibias and femurs were collected for further analysis.
The CFU-GM assay was used to evaluate granulocyte-macrophage progenitor cells. BMCs from treated mice were cultured in methylcellulose with necessary supplements, including GM-CSF, for seven days at 37°C in a humidified 5% CO₂ incubator. Colonies containing at least 50 cells were counted using an inverted microscope. The CFU-S assay was performed to assess spleen colony formation. BMCs from treated animals were intravenously injected into irradiated recipient mice. The number of macroscopic colonies in the spleen was counted after 12 days, following fixation in Bouin’s solution [2].

The HPP-CFC assay measured high proliferative potential colony-forming cells (HPP-CFCs). Bone marrow samples were cultured in a bilayer agar system supplemented with conditioned media from WEHI 3B and L929 cell lines. After 14 days of incubation, colonies were stained using INT (2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl tetrazolium chloride) to visualize viable cells. Colonies larger than 2 mm in diameter were counted. To determine whether AcSDKP protected long-term repopulating cells, bone marrow from DOX-AcSDKP-treated and DOX-treated mice was transplanted into lethally irradiated recipient mice. Bone marrow cells were harvested from donor male mice on day 7 post-DOX treatment and injected intravenously into female recipients at various concentrations. Recipient mortality was monitored for up to five months [2].

To verify whether hematologic reconstitution in recipient mice was endogenous or derived from transplanted cells, Y-chromosome PCR analysis was conducted. Genomic DNA from peripheral blood cells of surviving recipients at five months post-transplantation was analyzed using primers specific to the Y chromosome. DNA samples were amplified through 35 PCR cycles, and actin cDNA fragments were used as a control. PCR products were visualized on agarose gels stained with ethidium bromide and analyzed with NIH Image software [2].

Discussion
1) The study examined the effects of hyperthermic treatment at 43°C on normal hematopoiesis derived from donor or remission bone marrow, as well as leukemic progenitor cells. The reported results highlight the idea that different progenitor cell types exhibit varying levels of heat sensitivity. The granulocyte-macrophage colony-forming units (CFU-GM) are more resistant to heat exposure than erythroid progenitors, specifically burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E). Leukemic progenitor cells (CFU-AML) show significantly greater sensitivity to heat, experiencing a four-log reduction in viability after 90 minutes at 43°C, whereas normal progenitor cells exhibit less than a 50% reduction in viability under the same conditions. The detection threshold for clonogenic assays is a four-log reduction, but extrapolated data suggests that extending heat exposure to 120 minutes could increase leukemic cell depletion to a five-log reduction, with normal progenitor cells experiencing only a one-log reduction [1].

Additionally, the study investigated the protective effects of serum during heat treatment finding that while serum provides moderate protection to normal progenitor cells, it does not mitigate the heat-induced reduction in leukemic progenitor cells. This suggests that hyperthermia selectively targets leukemic cells more effectively than normal hematopoietic cells, and serum’s protective role is not sufficient to alter this outcome.

The study further examined the impact of Goralatide on the proliferative activity of normal, remission, and leukemic progenitor cells, illustrating that under control conditions, erythroid progenitor cells are highly proliferative, with 38% of CFU-E and 30% of BFU-E cells in the S-phase of the cell cycle. CFU-GM, in contrast, shows the lowest proliferative activity, with only 10% of cells in S-phase. There were no significant difference in proliferation between progenitor cells from normal and remission bone marrow, leading researchers to use the term “normal” to encompass both sources [1].
A 21-hour incubation with 10⁻⁹ M Goralatide significantly reduced the proliferative activity of all three normal progenitor subsets, bringing the percentage of S-phase cells to less than 7%. However, leukemic progenitor cells (CFU-AML) display exceptionally high proliferative activity, with over 60% of cells in the S-phase, and remain unaffected by Goralatide treatment. It was demonstrated that while Goralatide reduces the proliferation of normal progenitor cells, it does not impact overall cell viability, except for the CFU-E subset, which decreases to 50% of its original number. In leukemic bone marrow, the total number of nucleated cells and progenitors experiences only a slight decrease after incubation with Goralatide [1].

The differing effects of Goralatide on normal versus malignant progenitor cells have important implications for hyperthermic treatment, demonstrating that Goralatide pre-treatment significantly enhances the heat resistance of normal progenitor cells by reducing their proliferative activity. This protective effect is not observed in leukemic progenitor cells, which remain highly sensitive to hyperthermic treatment even after Goralatide incubation. As a result, Goralatide effectively increases the therapeutic index of hyperthermic purging by selectively protecting normal hematopoietic cells while leaving leukemic cells vulnerable to heat-induced cell death.

Overall, the study provides compelling evidence that hyperthermia preferentially targets leukemic progenitor cells while sparing normal hematopoietic cells to a significant extent. The protective effects of serum on normal cells are moderate but do not interfere with the hyperthermic reduction of leukemic cells. Goralatide reduces the proliferative activity of normal progenitor cells without compromising their viability, except for CFU-E, which experiences a moderate reduction. However, Goralatide does not influence the proliferative activity of leukemic cells, which remain highly active. This differential response enhances the therapeutic potential of hyperthermic treatment when combined with Goralatide, as it selectively protects normal cells from heat-induced damage while leaving leukemic cells highly susceptible. This finding suggests a promising strategy for improving hyperthermic purging in leukemia treatment [1].

2) The study performed by the research team of Massé et al investigated the effects of AcSDKP on the survival of mice treated with lethal doses of DOX, focusing on the mode, timing, and schedule of administration. Initially, mice were given a continuous infusion of AcSDKP for three days, beginning either 24 or 48 hours before the first DOX injection. The results showed that DOX alone induced 65% mortality with a median survival time of 18 days. However, when AcSDKP infusion began 48 hours before DOX, mortality significantly decreased to 27%, and median survival time increased to over 42 days. When the infusion started only 24 hours before DOX, survival was not significantly improved. This indicated that the timing of AcSDKP administration played a crucial role, with the 48-hour pre-treatment window providing the best protective effect [2].

To simplify the treatment protocol, AcSDKP was also administered via subcutaneous injection 48 hours before DOX. The results were comparable to those obtained with minipump infusion. Further, different schedules of AcSDKP injections were compared, using the same total dose of 7.2 μg/mouse, but varying the number of injections. The best survival benefit was observed with six or nine injections over multiple days, significantly increasing MST to 60 days. In contrast, single or three-dose injections were less effective, showing that multiple, staggered doses offered the greatest protection.
The study also examined how AcSDKP influenced the recovery of hematopoietic progenitor cells in DOX-treated mice. Three key populations were analyzed: colony-forming unit granulocyte-macrophage (CFU-GM), high proliferative potential colony-forming cells (HPP-CFC), and colony-forming unit-spleen (CFU-S). DOX treatment alone led to a severe nadir in cell populations, with recovery taking up to 18 days. However, in mice pretreated with AcSDKP, CFU-GM recovery was significantly improved on days 7 and 11, particularly when AcSDKP was given 48 hours before DOX rather than 24 hours. Additionally, higher doses of AcSDKP including 7.2, 72, and 720 μg/mouse, had a pronounced effect on CFU-GM recovery, while lower doses of 0.072 and 0.72 μg/mouse were ineffective [2].

Similar improvements were observed in HPP-CFC recovery. Mice receiving AcSDKP 48 hours before DOX had increased HPP-CFC counts on days 14 and 18. Interestingly, even on day 3 (the nadir of cell populations), AcSDKP-treated mice showed a higher number of HPP-CFCs compared to DOX-only controls, indicating a protective effect. CFU-S recovery was also enhanced by AcSDKP, with significant improvements observed on days 7 and 11. Overall, these findings confirmed that AcSDKP accelerates hematopoietic recovery in DOX-treated mice, with the 48-hour pre-treatment window being the most effective [2].

Another important aspect of the study was the effect of AcSDKP on primitive stem cells, specifically long-term repopulating cells. The ability of AcSDKP to protect long-term repopulating cells was tested by transplanting bone marrow cells from AcSDKP-DOX-treated mice into lethally irradiated recipient mice. Results showed that survival was significantly higher in recipients of AcSDKP-DOX-bone marrow cells compared to those receiving DOX-bone marrow cells. Only 10⁵ AcSDKP-DOX-bone marrow cells were needed to achieve 100% survival in recipients, whereas 10⁶ DOX-bone marrow cells were required for the same effect. This suggested that AcSDKP protected primitive hematopoietic stem cells from DOX toxicity. To confirm whether hematopoietic reconstitution was donor-derived, Y-chromosome PCR analysis was performed in recipient mice that received sex-mismatched transplants. PCR results showed that over 75% of peripheral blood cells in surviving mice originated from donor cells, further proving that AcSDKP effectively preserved functional stem cells [2].

Finally, the study explored whether granulocyte-colony stimulating factor (G-CSF) could enhance the protective effects of AcSDKP. Mice received AcSDKP in six SC injections starting 48 hours before DOX, followed by G-CSF injections on days 3–6 post-DOX. CFU-GM recovery was compared between groups receiving AcSDKP-DOX, G-CSF-DOX, and the combined AcSDKP-G-CSF-DOX regimen. Both AcSDKP and G-CSF alone improved CFU-GM numbers, but their combination resulted in an even greater recovery across all G-CSF doses tested. This suggested a synergistic effect between AcSDKP and G-CSF in promoting bone marrow recovery after DOX-induced damage.

In conclusion, the study demonstrated that AcSDKP significantly reduced DOX-induced mortality and improved hematopoietic recovery by protecting stem and progenitor cells. The best protective effect was achieved when AcSDKP was administered 48 hours before DOX in multiple doses or continuous infusion. Additionally, AcSDKP preserved LTRCs, ensuring long-term hematopoietic reconstitution, and its effects were further enhanced when combined with G-CSF. These findings highlight AcSDKP as a potential therapeutic agent to mitigate chemotherapy-induced bone marrow toxicity [2].

Disclaimer

**LAB USE ONLY**
*This information is for educational purposes only and does not constitute medical advice. THE PRODUCTS DESCRIBED HEREIN ARE FOR RESEARCH USE ONLY. All clinical research must be conducted with oversight from the appropriate Institutional Review Board (IRB). All preclinical research must be conducted with oversight from the appropriate Institutional Animal Care and Use Committee (IACUC) following the guidelines of the Animal Welfare Act (AWA).

 

Citations

[1] Wierenga PK, Brenner MK, Konings AW. Enhanced selectivity of hyperthermic purging of human progenitor cells using Goralatide, an inhibitor of cell cycle progression. Bone Marrow Transplant. 1998 Jan;21(1):73-8. doi: 10.1038/sj.bmt.1701045. PMID: 9486498.

[2] Massé A, Ramirez LH, Bindoula G, Grillon C, Wdzieczak-Bakala J, Raddassi K, Deschamps de Paillette E, Mencia-Huerta JM, Koscielny S, Potier P, Sainteny F, Carde P. The tetrapeptide acetyl-N-Ser-Asp-Lys-Pro (Goralatide) protects from doxorubicin-induced toxicity: improvement in mice survival and protection of bone marrow stem cells and progenitors. Blood. 1998 Jan 15;91(2):441-9. PMID: 9427696.

 

 

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