Recombinant interferon-γ inhibits the in vitro proliferation of human myeloma cells

Summary. Interferon-α (IFN-α), interferon-γ (IFN-γ) and dexamethasone (DEX) have shown anti-tumour effects in multiple myeloma (MM) cells. Bone marrow plasma cells from 39 MM patients were cultured to clarify the intensity and specific activity of each compound on bromo-deoxyuridine (BrdUrd) uptake and immunoglobulin (Ig) secretion. BrdUrd uptake was inhibited by recombinant human IFN-γ (100 U/ml) and by DEX (10⁻⁶ m ). The stimulation index (StI), i.e. labelling index (LI) of treated samples/controls, was 0·49 0·009 (mean standard error of the mean, MSEM), P =0·0003, and 0·52·0·07 (MSEM), P <0·0001, respectively. Ig secretion was reduced by IFN-α (100 U/ml) and DEX. The secretion index (SI), i.e. Ig quantitation of treated samples/controls, was 0·04 (MSEM), P <0·0001, and 0·52·0·04 (MSEM), P <0·0001, respectively. Finally, IFN-γ inhibits BrdUrd uptake only and IFN-α secretion only. In 18 patients the simultaneous addition of IFN-α plus IFN-γ mainly paralleled the effect of IFN-γ on BrdUrd uptake and IFN-α on secretion, but did not result in any additive or synergistic effect, though both BrdUrd uptake and Ig secretion were decreased to about the same extent as with DEX. These data indicate that the combination of IFN-α plus IFN-γ and DEX are the strongest inhibitors of both BrdUrd uptake and secretion. Since IFN-α and IFN-γ appear to have a different mechanism of action, their combined use could be considered as a possible new treatment strategy.     

Incidence of apoptosis and cell proliferation in multiple myeloma: correlation with bcl-2 protein expression and serum levels of interleukin-6 (IL-6) and soluble IL-6 receptor

We evaluated the in vivo incidence of apoptosis and cell proliferation in multiple myeloma (MM) and investigated the correlation of both cellular events with histological tumour stage and grade, bcl-2 protein expression, serum IL-6 and sIL-6R. MATERIAL AND METHODS: The TUNEL method was used to assess apoptosis and immunohistochemistry to assess the expression of proliferating cell nuclear antigen (PCNA) and bcl-2 protein in 30 bone marrow biopsy specimens. The apoptotic index (AI) and proliferative index (PI) were defined as the percentage of TUNEL and PCNA positive plasma cells, respectively. RESULTS: The mean AI was 0.162% and the mean PI 27.44%. A positive correlation between AI and PI was found (r = 0.44, P = 0.017). PI was also correlated with tumour grade (P = 0.015). The mean bcl-2 protein expression was 70% and did not correlate with AI or PI, but was higher in specimens taken at first diagnosis than in specimens taken after response to treatment (P = 0.035). The mean serum IL-6 and sIL-6R values were 9.43 pg mL-1 and 47.27 ng mL-1, respectively. These parameters did not correlate with AI or PI. CONCLUSIONS: The results indicate that MM might be among the malignancies with very low incidence of apoptosis. Proliferative activity increased in parallel with tumour histological grade. A positive correlation between apoptosis and proliferation was observed, but the incidence of these two cellular events seems not to be related to the bcl-2 protein expression and the serum levels of IL-6 and sIL-6R.     

The gp 130 family cytokines IL-6, LIF and OSM but not IL-11 can reverse the anti-proliferative effect of dexamethasone on human myeloma cells

Summary. In order to understand the mechanisms supporting steroid escape in patients with multiple myeloma (MM), three IL-6 autocrine human myeloma cell lines, LP1, OPM2 and L363, have been treated with dexamethasone in the presence or absence of cytokines belonging to the gp 130 family: IL-6, LIF, OSM and IL-11. With pharmacological doses of dexamethasone, a dramatic growth arrest was observed in all the cell lines. IL-6 completely reversed this inhibition. Of note, this IL-6 induced reversion was still seen with very low amounts of IL-6 (12 pg/ml). Finally, whereas LIF and OSM had clear growth-promoting effects on OPM2 only, both cytokines (but not IL-11) reversed the dexa-methasone-induced growth arrest in all the cell lines. Therefore the high levels of IL-6 (ng/ml) observed in the MM intermediate milieu and the putative presence of LIF and OSM can easily counteract the effects of dexamethasone in vivo.     

Detection of interleukin-6 (IL-6) in human bone marrow myeloma cells by light and electron microscopy

We used an Avidin-Biotin peroxidase complex (ABC) immunoperoxidase technique to evaluate the localization of IL-6 of human bone marrow cells in multiple myeloma (MM). The cellular distribution of IL-6 was determined at light and electron microscopic levels. The author's study indicated that cytoplasmic IL-6 was detected only in the myeloma cells of bone marrow cells. Immunoelectron microscopic (immuno-EM) study showed positive reactivity mainly in the perinuclear space (PNS), well-developed rough endoplasmic reticulum (RER), and Golgi area.     

Interleukin-1 in multiple myeloma: producer cells and their role in the control of IL-6 production

We studied the role of interleukin (IL)-1β in patients with multiple myeloma. By in situ hybridization and immunochemistry, myeloid and megakaryocytic cells expressed high levels of the IL-1β gene and produced IL-1β. Myeloma cells less potently expressed the IL-1β gene and IL-1β protein. IL-1β gene expression was not constitutive since it was detected in the bone marrow myeloma cells of two patients, unlike circulating tumoural cells. In addition, nine myeloma cell lines failed to express the IL-1β gene and this expression could not be induced by 12 different cytokines. We demonstrated that IL-1 was mainly responsible for IL-6 production in the tumoural environment through a PGE₂ loop. In fact, an IL-1 receptor antagonist (IL-1RA) blocked PGE₂ synthesis and IL-6 production by 80%; this blockage could be reversed by adding synthetic PGE₂. Similar findings were found with indomethacin, an inhibitor of cyclooxygenase that blocks PGE₂ synthesis. Taken together, these data emphasize the possibility of blocking IL-1 by using IL-1RA or other antagonists in order to block IL-6 production, which is a major tumoural survival and proliferation factor.     

Retinoic acid inhibits the growth of human myeloma cells in vitro

Retinoic acid has been shown to induce growth inhibition in a variety of cell types including human myeloma cell lines. Bone marrow plasma cells from 31 multiple myeloma (MM) patients were cultured to investigate the activity of 13-cis-retinoic acid (cRA), all-trans-retinoic acid (tRA), interferon-α (IFN-α), interferon-γ (IFN-γ), and dexamethasone (DEX), alone or in combination, on in vitro proliferation and immunoglobulin (Ig) secretion. Both cRA and tRA inhibited proliferation: the labelling index (LI) of treated cultures/controls, was 0.47±0.05 (mean ± standard error mean, M ± SEM) P < 0.0001, and 0.67 ± 0.04 (M ± SEM), P < 0.0001, respectively. The inhibitory effect of cRA was significantly superior to tRA ( P = 0.0129) and IFN-α, similar to IFN-γ and DEX. The combinations of cRA + IFNα, tRA + IFN-γ, tRA + DEX did not show any synergistic effect on myeloma proliferation. In contrast, the combination cRA + DEX (0.29 ± 0.04, M±SEM) markedly increased the effect of both cRA and DEX used as single agents.
Ig synthesis was not significantly affected by CRA, tRA, IFN-γ and the combination tRA + IFN-γ, As expected, only IFN-α ( P 0.002) and DEX ( P 0.001) inhibited Ig production. The combinations cRA + IFN-α, cRA-DEX and tRA + DEX decreased Ig secretion to the same extent as IFN-α and DEX alone respectively. In conclusion, our data indicate that tRA and especially cRA strongly inhibited plasma cell proliferation but had no effect on Ig synthesis. The combination of cRA + DEX showed the highest degree of inhibitory activity of all cytokines. alone or in combination.     

TNF and IL-6 are potent growth factors for OH-2, a novel human myeloma cell line

Abstract: A novel human myeloma cell line, OH-2, was established from pleural fluid of a myeloma patient in end stage of the disease. Effects of cytokines on proliferation were analyzed by measuring uptake of ³H-thymidine. Cell surface antigens were detected by flow cytometry. The cell line is dependent on IL-6 for growth and proliferates in response to TNF. There is synergy between the stimulatory response of TNF and IL-6. The cells express both the p55 and p75 TNF receptors. Neutralizing anti-IL-6 did not inhibit TNF-mediated proliferation, showing that TNF acts through a pathway that is independent of IL-6. TNF was more potent than IL-6 in stimulating the growth of primary myeloma cultures (>99% pure) from the same patient (OH-2-PC), indicating that TNF in selected myeloma patients has a growth-promoting effect equal to IL-6. OH-2 cells produce and secrete monoclonal IgG-kappa.     

Dexamethasone plus retinoids decrease IL-6/IL-6 receptor and induce apoptosis in myeloma cells

Interleukin 6 (IL-6) is the most important known growth factor for multiple myeloma, and IL-6 signalling pathways are potential targets for therapy. We hypothesized that interfering with the IL-6 signalling pathway at more than one level would be more effective than a single block in inhibiting proliferation of myeloma cells. Accumulating data support the concept that glucocorticoids down-regulate IL-6, whereas retinoic acid derivatives (RA) down-regulate IL-6R in myeloma. We found that all- trans RA (ATRA), 13- cis -RA and 9- cis -RA each similarly inhibited growth of RPMI 8226 myeloma cells and that addition of dexamethasone (DEX) added to RA growth inhibition. The major effects of retinoids were to reduce the proliferative fraction and induce apoptosis whereas DEX increased the apoptotic fraction. When combined, apoptosis was enhanced. Effects of RA + DEX were also least able to be overcome by exogenous IL-6. RA decreased IL-6R levels and addition of DEX to RA delayed recovery of IL-6R levels compared with RA alone. Since RPMI 8226 cells have undetectable IL-6, we investigated U266B1 cells and found that RA and DEX decreased both IL-6 secretion and IL-6 RNA levels. Mechanistically, IL-6R down-regulation by RA was enhanced by DEX, whereas IL-6 protein and RNA levels were reduced by DEX and by RA. In summary, combinations of RA + DEX were not only more effective in inhibiting myeloma cells growth by the dual mechanisms of decreasing proliferative fraction and increasing apoptotic fraction, but were also less able to be overcome by IL-6.     

Serum interleukin-6 (IL-6) and interleukin-4 (IL-4) in patients with multiple myeloma (MM)

In this study we determined, in patients with multiple myeloma (MM), serum levels of IL-4 and IL-6 at diagnosis and during the course of the disease, seeking a correlation with disease activity and prognosis. We studied 54 MM patients, 41 of whom responded to chemotherapy whilst 11 were resistant. At diagnosis, IL-6 was increased in 66% of patients (median 35.5 pg/ml) whereas IL-4 was low (median 4 pg/ml) in 75% of patients. In responding patients, IL-4 increased in remission (median 25 pg/ml), whereas IL-6 decreased (median 4 pg/ml). In chemotherapy-resistant patients, IL-6 and IL-4 values remained stable during the course of the disease.     

IL-4 improves the detection of cytogenetic abnormalities in multiple myeloma and increases the proportion of clonally abnormal metaphases

In the present study the incidence of abnormal karyotypes and the number and proportion of abnormal metaphases obtained in multiple myeloma (MM) using three culture conditions were compared: unstimulated culture (72 h), IL-6/GM-CSF-stimulated culture (120 h) and IL-4-stimulated culture (120 h). The three types of culture conditions were assessed simultaneously on bone marrow samples from 30 consecutive myeloma patients. In addition DNA content (DNA ploidy and cell cycle) was analysed by flow cytometry. The number of MM samples with clonal karyotypic abnormalities was higher after IL-4-stimulated cultures (53%) than it was after IL-6 + GM-CSF (37%) and unstimulated (30%) cultures. The benefit of IL-4 was also observed in cases with low numbers of plasma cells in the bone marrow, in early clinical stages and in untreated patients. In those cases in whom clonal chromosomal abnormalities were detected by the three culture methods, the cytogenetic findings were always identical. According to our results the addition of IL-4 to the cultures of bone marrow cells in MM increases the number of abnormal metaphases.     

IL-6和DKK1在多发性骨髓瘤中表达的意义

目的：研究多发性骨髓瘤（MM）患者中IL-6、DKK1的表达水平,阐明其在MM发病中的临床意义。方法：采用酶链免疫和化学发光法对60例MM患者和50例对照者血清中IL-6、DKK1的表达量检测并进行比较。结果：IL-6、DKK1在对照者中表达低于MM患者,两者比较差异有统计学意义（P〈0.01）;MM患者中IL-6、DKK1的表达水平与临床分期高低有关（P〈0.01）;IL-6和DKK1表达有正相关关系（rs=0.7381,P〈0.01）。结论：IL-6和DKK1的联合检测可作为MM患者病变严重程度的早期诊断指标,为临床治疗提供帮助。     

Diagnostic value of serum IL-6 level in monoclonal gammopathies

Summary. The serum level of IL-6 was reported to reflect disease severity in patients with multiple myeloma. We used a specific radioimmunoassay to measure the level of IL-6 in 239 serum samples in which a monoclonal gammopathy was identified for the first time. The same sample was used for the measurement of serum C reactive protein and serum albumin. Then, an inventory of clinical and biological features allowed us to classify these patients into five groups: monoclonal gammopathy of undetermined significance (MGUS: 128), multiple myeloma (MM:66), Waldenström's macroglobulinaemia (WM:27), non-Hodgkin's lymphoma (NHL: 11) and chronic lymphocytic leukaemia (CLL: 7). The number of patients with serum IL-6 (S-IL-6) level >0.335 ng/ml (upper limit in normal sera) was significantly higher in the MM group (35%; Confidence Interval (CI) 23.5–46.5) compared with the MGUS group (15%; CI 8.8–21.2). The distribution of S-IL-6 levels was also significantly different between the groups (Mann-Whitney test: P< 0.01). High S-IL-6 levels were measured in 5/11 patients with NHL and 9/27 patients with WM. The distribution of S-IL-6 levels in these groups was the same as that in MGUS or MM groups. In patients with MM, elevated S-IL-6 levels were associated with haemoglobin level <100 g/l (P< 0.005). bone marrow plasmocytosis >50% (P<0.05) and stages II and III in the Durie & Salmon staging system (P< 0.005). The S-IL-6 level was also related to light chain component excretion in urine (P<0.01) and M component serum level for IgA (P<0.01). In patients with MGUS, the S-IL-6 level correlated with serum CRP level (P<0.05). serum lactate dehydrogenase (P< 0.05) and serum ferritin (P < 0.01). We conclude that the S-IL-6 level is a marker of high tumour burden in multiple myeloma. However, S-IL-6 level can be increased in patients with MGUS in relation to inflammatory parameters. Therefore the S-IL-6 level does not demonstrate high predictive value for the diagnosis of MM in patients with newly identified monoclonal gammopathy.     

The effects on growth and survival of IL-6 can be dissociated in the U-266-1970/U-266-1984 and HL407E/HL407L human multiple myeloma cell lines

Several studies have documented IL-6-dependent growth promotion of murine and human neoplastic plasma cells. However, it is well known that human multiple myeloma (MM) cells in vitro show a considerable degree of heterogeneity concerning growth and survival requirements. This heterogeneity, which probably reflects overlapping effects of feeder cells, interleukin 6 (IL-6) and components of fetal calf serum (FCS) as well as tumour heterogeneity in vivo , has hampered the elucidation of molecular mechanisms underlying the effects of IL-6. In an attempt to dissociate growth and survival promotion of IL-6, we have studied two pairs of human MM cell lines, HL407E/HL407L and U-266-1970/U-266-1984, selected to represent different stages of in vitro tumour progression and dependence of feeder cells and exogenous IL-6. We demonstrated that exogenous IL-6, in the presence of FCS, conveyed: (a) a strong growth stimulatory effect with weak or no survival promotion in HL407L and U-266-1970 cells; (b) promotion of survival with no effects on growth in HL407E cells; (c) no growth or survival promotion to U-266-1984. Moreover, our results suggested that IL-6 may enhance apoptosis in U-266-1970/U-266-1984 cells, and that FCS may interfere with IL-6 in its growth stimulatory effect. The relative dissociation of growth, survival and apoptotic effects of IL-6 leads to the conclusion that the HL407E/HL407L and U-266-1970/U-266-1984 pairs of cell lines provide a useful human model system to study molecular mechanisms underlying these separate events.     

High incidence of deletions but infrequent inactivation of the retinoblastoma gene in human myeloma cells

Summary. We have studied the retinoblastoma (RB-1) susceptibility gene status and pRB expression in 22 human myeloma cell lines (HMCL) and in 10 patients with advanced multiple myeloma (MM). Deletions of the RB-1 gene were observed in 81% (17/21) of the informative HMCL, regardless of their paracrine or autocrine interleukin-6 (IL-6) status. Among the deleted HMCL, only one (U266) had a biallelic deletion and lacked pRB expression. Monoallelic deletions had no consequence on the RB-1 gene activation and pRB expression. One patient of 10 presented the same biallelic deletion as U266 and six of 10 had monoallelic deletions. We conclude that monoallelic deletions of the RB-1 gene are frequent in HMCL and MM patients but have no consequence on gene activation and pRB expression.     

Bone marrow angiogenesis and circulating plasma cells in multiple myeloma

Bone marrow (BM) angiogenesis is increased in multiple myeloma (MM) and has prognostic significance. The presence of circulating plasma cells (PCs) in MM is associated with a poorer prognosis. We examined BM biopsies obtained at diagnosis of MM for angiogenesis, and correlated the microvessel density (MVD) with the presence of circulating PCs. There was a positive correlation between the absolute number of circulating PCs and the mean MVD. This relationship was independent of the disease activity and of the PC burden in the marrow. The increased angiogenesis may promote plasma cell proliferation and enable PC migration into the circulation.     

Methylenetetrahydrofolate reductase genotype does not play a role in multiple myeloma pathogenesis

Methylenetetrahydrofolate reductase (MTHFR) plays an important role in carcinogenesis. A decreased incidence of cancer has been reported in the presence of MTHFR 677TT, 1298AC and 1298CC polymorphic variants. We have analysed the MTHFR genotype in 107 multiple myeloma (MM) patients and 86 controls. The MM and control polymorphisms frequencies were: 34% and 48% for 677CC, 53% and 41% for 677CT, 12% and 11% for 677TT; 36% and 43% for 1298AA, 51% and 44% for 1298AC; and 12% and 13% for 1298CC respectively. No statistically significant differences were observed. In addition, no differences were seen according to MM stage, presence of p16 gene hypermethylation or response to treatment.     

Cell proliferation of myeloma plasma cells: comparison of the blood and marrow compartments

The plasma cell labeling Index (PCLI), a measure of marrow plasma cells in S phase of the cell cycle, provides a good estimate of the proliferative capacity of the malignant clonal plasma cells. Multiple studies have also demonstrated its prognostic value in multiple myeloma (MM). Clonal plasma cells have been demonstrated in the peripheral blood of patients with multiple myeloma. The labeling index of these circulating cells can also be determined by a method similar to that employed for marrow plasma cells. The goal of this study was to compare the proliferation kinetics of plasma cells in the marrow to that in the circulation. The PCLI was estimated on peripheral blood (PBLI) and bone marrow aspirates (BMLI) using a slide-based bromodeoxyuridine (BrdU) immunofluorescence microscopy technique. One hundred seventeen patients who had simultaneous estimation of the PBLI and BMLI and who had > or =90% of the blood cIg+ cells identified as monoclonal plasma cells were studied. The PBLI was generally lower than the BMLI (median difference 0.4) and correlated with the BMLI (rho = 0.491, P < 0.0001). Twenty-seven patients with PBLI higher than BMLI had a poorer prognosis, with median survival of 2 months from the time of the labeling index determination, compared to 12 months for the remaining 90 patients (P = 0.01). Myeloma plasma cells circulating in the peripheral blood are capable of proliferation, albeit at a slower rate compared to those in the marrow. These differences reflect a more favorable microenvironment in the marrow likely resulting from the differences in the cytokine levels and supporting stromal cells in the marrow.     

Serum interleukin-6 has no discriminatory role in paraproteinaemia nor a prognostic role in multiple myeloma.

We determined interleukin-6 (IL-6) levels in the serum of 212 well-defined patients with newly diagnosed paraproteinaemia and evaluated its discriminatory value and prognostic role in multiple myeloma (MM). Results were compared with serum neural cell adhesion molecule and beta-2-microglobulin, both established prognostic MM markers. Paraproteinaemia-related diagnoses were: MM (60), other haematological diseases (46), solid tumours (35), autoimmune diseases (17) and monoclonal gammopathy of unknown significance (MGUS) (54). The range of IL-6 levels in all diagnostic groups overlapped widely and did not serve as a discriminatory marker in newly diagnosed paraproteinaemia even when patients with infection or fever (42) were excluded. In MM high IL-6 levels (>/= 50 pg/ml) were not associated with a shorter survival (P = 0.24). We compared our results with 20 published studies on serum IL-6 in paraproteinaemia and/or MM. IL-6 data have to be related to the assay used (bio- or immunoassay) and to the status of MM (newly diagnosed, during therapy, progressive disease). We conclude that serum IL-6 is not specific for paraproteinaemia-related diseases and will not serve as a reliable discriminatory or prognostic marker in paraproteinaemia and MM.     

Recombinant interferon-gamma inhibits the growth of IL-6-dependent human multiple myeloma cell lines in vitro.

Recombinant human IFN-gamma (100-1000 U/ml) inhibited the IL-6-induced growth of 2 human IL-6-dependent multiple myeloma (MM) cell lines U-1958 and U-266-1970 in vitro. In contrast, the U-1996 line, independent of IL-6 for maintenance at a slow growth rate but responding to IL-6 by increased proliferation, and the IL-6-independent U-266-1984 were refractory to the anti-proliferative effect of IFN-gamma. The effect of IFN-gamma in the sensitive MM cell lines was cytostatic in U-266-1970, and cytostatic and cytotoxic in U-1958. Northern blot analysis revealed that the growth inhibition of the IL-6-dependent MM cell line U-1958 was not due to down-regulation of IL-6 receptor mRNA expression and that the differential sensitivity to IFN-gamma was not due to differences in IFN-gamma receptor expression. The growth inhibition was not a consequence of an IFN-gamma-induced terminal differentiation as flow cytometric analyses demonstrated an arrest in all phases of the cell cycle. IFN-alpha inhibited the growth in 3 of the 4 cell lines tested. The results thus suggest that the particular MM phenotype, which includes IL-6 dependency for survival and growth, may also be characterized by IFN-gamma sensitivity. Furthermore, the study demonstrates that MM cell lines are not simultaneously sensitive to IFN-gamma and alpha, indicating that the mechanisms of action of the two types of IFN are distinct.