Resistance mechanisms of hematopoietic and leukemic stem cells

Krwiotwórcze komórki macierzyste (HSC) są szczególnym typem somatycznych komórek macierzystych. Cechuje je zdolność do nieograniczonej liczby podziałów oraz różnicowania we wszystkie typy komórek krwi. Pula HSC musi wystarczyć na cały okres życia organizmu. Wszystkie zmiany genetyczne w komórce macierzystej zostają utrwalone w komórkach potomnych i mogą prowadzić do zaburzeń hematopoezy. Istnieje wiele mechanizmów chroniących somatyczne HSC. Część HSC pozostaje w stanie spoczynku, czyli fazie G0 cyklu komórkowego, co obniża ryzyko pojawienia się mutacji. Komórki te cechują się podwyższoną ekspresją białek związanych z opornością na apoptozę, naprawą uszkodzeń DNA oraz usuwaniem toksyn. Inne białka zapobiegają ich zniszczeniu przez komórki swoistej i nieswoistej odpowiedzi immunologicznej. Mikrośrodowisko szpiku kostnego zapewnia również ochronę HSC. Podobne mechanizmy wpływają na oporność tak zwanych białaczkowych komórek macierzystych (LSC). Na oporność LSC wpływają również mutacje pojawiające się w procesie nowotworzenia. Istnienie nowotworowych komórek macierzystych (CSC) uważa się za jedną z głównych przyczyn niepowodzeń terapeutycznych — chemio- i radioterapia zmniejszają liczbę komórek białaczkowych w organizmie, ale pozostające po zakończeniu leczenia CSC powodują wznowę. Poznanie mechanizmów ochronnych HSC ma istotne znaczenie, gdyż pozwala na zrozumienie podłoża niektórych chorób hematologicznych oraz poszukiwanie nowych rozwiązań terapeutycznych.Hematopoietic stem cells (HSC) are a special type of somatic stem cells. They are characterized by the ability to divide an unlimited number of times and to differentiate into all types of blood cells. The pool of HSC must therefore be sufficient for the whole life of an organism. All genetic alterations of a stem cell will be retained by its daughter cells and they may lead to disturbances of hematopoiesis. There are several mechanisms that protect somatic HSC. Part of HSC remain inquiescent state, the G0 phase of the cell cycle, which reduces the risk of mutations. These cells are also characterized by increased expression of proteins associated with apoptosis resistance, DNA repair and toxin removal. Other surface proteins provide protection against attack by specific and/or nonspecific immune system cells. Also, HSC are protected by bone marrow microenvironment. Similar mechanisms affect the resistance of the so-called leukemic stem cells (LSC). Resistance of these cells is also influenced by mutations that occur during carcinogenesis. Presence of cancerstem cells (CSC) is considered to be a major cause of treatment failure: chemo-and radiotherapy both reduce the number of leukemic cells in the body, but CSC which remain after treatment may cause recurrence of the disease. Understanding resistance mechanisms of HSC might exert a significant impact on further developments in medicine. Foremostly, such knowledge would permit understanding the background and fine details of some hematologic disorders as well as developing novel therapeutic strategies

Resistance mechanisms of hematopoietic and leukemic stem cells

Krwiotwórcze komórki macierzyste (HSC) są szczególnym typem somatycznych komórek macierzystych. Cechuje je zdolność do nieograniczonej liczby podziałów oraz różnicowania we wszystkie typy komórek krwi. Pula HSC musi wystarczyć na cały okres życia organizmu. Wszystkie zmiany genetyczne w komórce macierzystej zostają utrwalone w komórkach potomnych i mogą prowadzić do zaburzeń hematopoezy. Istnieje wiele mechanizmów chroniących somatyczne HSC. Część HSC pozostaje w stanie spoczynku, czyli fazie G0 cyklu komórkowego, co obniża ryzyko pojawienia się mutacji. Komórki te cechują się podwyższoną ekspresją białek związanych z opornością na apoptozę, naprawą uszkodzeń DNA oraz usuwaniem toksyn. Inne białka zapobiegają ich zniszczeniu przez komórki swoistej i nieswoistej odpowiedzi immunologicznej. Mikrośrodowisko szpiku kostnego zapewnia również ochronę HSC. Podobne mechanizmy wpływają na oporność tak zwanych białaczkowych komórek macierzystych (LSC). Na oporność LSC wpływają również mutacje pojawiające się w procesie nowotworzenia. Istnienie nowotworowych komórek macierzystych (CSC) uważa się za jedną z głównych przyczyn niepowodzeń terapeutycznych - chemio- i radioterapia zmniejszają liczbę komórek białaczkowych w organizmie, ale pozostające po zakończeniu leczenia CSC powodują wznowę. Poznanie mechanizmów ochronnych HSC ma istotne znaczenie, gdyż pozwala na zrozumienie podłoża niektórych chorób hematologicznych oraz poszukiwanie nowych rozwiązań terapeutycznych

The Role of Complement Activating Collectins and Associated Serine Proteases in Patients With Hematological Malignancies, Receiving High-Dose Chemotherapy, and Autologous Hematopoietic Stem Cell Transplantations (Auto-HSCT)

We conducted a prospective study of 312 patients (194 with multiple myeloma, 118 with lymphomas) receiving high-dose conditioning chemotherapy and autologous hematopoietic stem cell transplantation (auto-HSCT). Polymorphisms of MBL2 and MASP2 genes were investigated and serial measurements of serum concentrations of mannose-binding lectin (MBL), CL-LK collectin and MASP-2 as well as activities of MBL-MASP-1 and MBL-MASP-2 complex were made. Serum samples were taken before conditioning chemotherapy, before HSCT and once weekly after (totally 4-5 samples); in minority of subjects also 1 and/or 3 months post transplantation. The results were compared with data from 267 healthy controls and analyzed in relation to clinical data to explore possible associations with cancer and with chemotherapy-induced medical complications. We found a higher frequency of MBL deficiency-associated genotypes (LXA/O or O/O) among multiple myeloma patients compared with controls. It was however not associated with hospital infections or post-HSCT recovery of leukocytes, but seemed to be associated with the most severe infections during follow-up. Paradoxically, high MBL serum levels were a risk factor for prolonged fever and some infections. The first possible association of MBL2 gene 3′-untranslated region polymorphism with cancer (lymphoma) in Caucasians was noted. Heterozygosity for MASP2 gene +359 A>G mutation was relatively frequent in lymphoma patients who experienced bacteremia during hospital stay. The median concentration of CL-LK was higher in myeloma patients compared with healthy subjects. Chemotherapy induced marked increases in serum MBL and MASP-2 concentrations, prolonged for several weeks and relatively slighter decline in CL-LK level within 1 week. Conflicting findings on the influence of MBL on infections following chemotherapy of myeloma and lymphoma have been reported. Here we found no evidence for an association between MBL deficiency and infection during the short period of neutropenia following conditioning treatment before HSCT. However, we noted a possible protective effect of MBL during follow-up, and suspected that to be fully effective when able to act in combination with phagocytic cells after their recovery

Combination of combretastatin A4 phosphate and doxorubicin-containing liposomes affects growth of B16-F10 tumors

The study aimed to check the effectiveness of anticancer therapy combining a vascular-disruptive drug (combretastatin phosphate, CA4P) and a liposomal formulation of a chemotherapeutic (doxorubicin). CA4P was synthesized in our laboratory according to a previously described procedure. The antivascular drug and long-circulating doxorubicin-loaded liposomes were used to treat B16-F10 murine melanoma experimental tumors. Seventy-four hours after drug administration, a decrease in the number of tumor blood vessels was apparent and necrotic areas within tumors were visible. Combination therapy consisting of alternate administrations of CA4P and liposomal doxorubicin yielded greater inhibition of tumor growth than monotherapies alone. The best therapeutic results were obtained with the antivascular drug administered intratumorally every second day at 50 mg/kg body mass. In the case of combined therapy, the best results were obtained when the vascular-disruptive agent (CA4P) and the antineoplastic agent (liposomal doxorubicin) were administered in alternation

Combination of IL-12 gene therapy and CTX chemotherapy inhibits growth of primary B16(F10) melanoma tumors in mice

We investigated suppression of murine B16(F10) melanoma tumor growth following a therapy which involved concomitant administration of cyclophosphamide and plasmid DNA bearing interleukin-12 gene. Since both therapeutic factors display antiangiogenic capabilities, we assumed that their use in blocking the formation of new blood vessels would result in augmented inhibition of tumor growth. This combined therapy regimen indeed resulted in a considerable suppression of tumor growth. We observed a statistically significant extension of treated animals' lifespan. Interestingly, the therapeutic effect was also obtained using a plasmid without an interleukin gene insert. This observation suggests that plasmid DNA, which has been widely applied for treating neoplastic tumors, contains element(s) that elicit immune response in mice

Properties of B16-F10 murine melanoma cells subjected to metabolic stress conditions

Neoplastic cells which co-form tumors are usually subjected to various stress factors, mainly hypoxia and shortage of nutrient factors. Such cells employ different strategies that permit their survival under such conditions. Experiments in vitro are usually carried out in the presence of 21% oxygen and medium supplemented with 10% FBS. Altering these parameters can approximate the in vivo conditions found within tumor mass. The present paper reports certain properties (especially ability to metastasize) of B16-F10 cells able to grow upon exposure to altered growth conditions (medium supplemented with 0.06% FBS or presence of 1% oxygen for 24 or 72 hours). These properties were compared with those of control cells cultured in the presence of 21% oxygen and in medium supplemented with 10% FBS. Some properties of the cells exposed to medium supplemented with 0.06% FBS differ from those of cells cultured under low oxygenation conditions (ability to form metastases, to migrate, or to express various proteins). Only the partial deprivation of oxygen did increase both the number of migrating cells and the number of metastases formed. Serum deficiency enhanced only the cell ability to metastasize, but not to migrate. It appears that cultured B16-F10 cells employ different adaptation strategies under conditions of oxygen shortage and those of serum deficiency. Under oxygen deprivation, such cells most likely undergo an epithelial-mesenchymal transition, whereas serum deficiency ("starvation"), while increasing the tumorigenicity of B16-F10 cells, does not induce the epithelial-mesenchymal transition