Mechanisms by which interferon potentiates chemotherapy

Cytokines in breast cancer

In recent decades many advances have occurred in the understanding of the role of cytokines in breast cancer. New signalling pathways of interleukin (IL)-1 family, IL-6, IL-11, IL-18, interferons (IFNs) and interferon regulatory factors 1 (IRF-1) and 2 (IRF-2) have been found within tumour microenvironments and in metastatic sites. Some cytokines (IL-1, IL-6, IL-11, TGFbeta) stimulate while others (IL-12, IL-18, IFNs) inhibit breast cancer proliferation and/or invasion. Similarly, high circulating levels of some cytokines seem to be favourable (soluble IL-2R) while others are unfavourable (IL-1beta, IL-6, IL-8, IL-10, IL-18, gp130) prognostic indicators. So far IL-2, IFNalpha, IFNbeta and occasionally IFNgamma, IL-6, IL-12 have been the cytokines used for anti tumour treatment of advanced breast cancer either to induce or increase hormone sensitivity and/or to stimulate cellular immunity. Disappointing results occurred in most trials; however, two long-term pilot studies suggest that IL-2 and IFNbeta, when used appropriately can have a positive effect on clinical benefit and overall survival of patients with minimal residual disease after chemotherapy or with disseminated disease controlled by conventional endocrine therapy.

IL-2-mediated augmentation of NK-cell activity and activation antigen expression on NK- and T-cell subsets in patients with metastatic melanoma treated with interferon-alpha and DTIC

Considering that well-defined and comprehensive immunological monitoring is the basis for the evaluation of the obtained immunmodulatory effects, we evaluated NK-cell activity, the number of CD3+ CD4+, CD3+ CD8+ T cells and CD16+ CD56+ NK cells, as well as the expression of activation antigens, CD69, CD38 and HLA-DR on CD56+ NK cells, CD8+ and CD3+ T cells, simultaneously with IL-2 and TNF-alpha production, during chemoimmunotherapy with dacarbazine (DTIC) and interferon-alpha (IFN-alpha) in 39 patients with metastatic melanoma. In the first cycle of therapy, there was a significant rise in NK-cell activity, CD4+ T helper cell number, CD4/CD8 T-cell ratio, and the expression of activation antigens CD69 and CD38, on NK and T cells, respectively. However, in the following cycles there was a significant increase only in activation antigens without an increase in the percent or activity of NK cells. The early, but transient, immunopotentiation, present only in the first cycle of combined DTIC and IFN-alpha therapy, suggests that, in spite of increased IL-2 level, associated with augmented NK-cell activity, this therapy has a limited effect probably owing to the adverse effect of persistently high level of TNF-alpha in metastatic disease.

Acquired factor VIII inhibitor in a patient with chronic myelogenous leukemia receiving interferon-alfa therapy

OBJECTIVE

To report a case of an acquired factor VIII inhibitor associated with the use of interferon-alfa.

CASE SUMMARY

A 58-year-old white man with newly diagnosed chronic myelogenous leukemia (CML) was initially treated with hydroxyurea. Interferon-alfa therapy was started six weeks later in order to enhance the response, with gradual reduction and eventual discontinuation of hydroxyurea. Interferon-alfa was continued for one year. Following bone marrow aspiration at one year, the patient developed significant bleeding and bruising at the site of extraction. His hemoglobin decreased from 11.3 to 9.3 g/dL and his activated partial thromboplastin time was elevated at 72 seconds. The factor VIII concentration was 0.02 units/mL; factor VIII inhibitor concentration was 58 Bethesda units. A diagnosis of an acquired factor VIII inhibitor was made, and the patient was treated with activated factor VII concentrates and prednisone. Interferon-alfa was discontinued, and the inhibitor subsequently disappeared over the next six weeks. The patient did not have any further bleeding problems.

DISCUSSION

Acquired factor VIII inhibitors other than in patients with hemophilia are rare. To date, there are no reported cases of factor VIII inhibitors associated with CML. Moreover, the temporal association with interferon-alfa administration suggests a causal relationship. There are only two previous case reports suggesting interferon-alfa as a cause of factor VIII inhibitors.

CONCLUSIONS

Induction of factor VIII inhibitors is a serious potential complication of therapy with interferon-alfa. We suggest that a diagnosis of an acquired factor VIII inhibitor be considered in patients who experience unexplained bleeding with interferon-alfa therapy.

Active vs. passive resistance, dose-response relationships, high dose chemotherapy, and resistance modulation: a hypothesis

With chemotherapy, the in vitro and clinical dose-response curve is steep in some situations, but is relatively flat in others, possibly due to the mechanism by which tumors are resistant to chemotherapy. For tumors with resistance due to factors that actively decrease chemotherapy efficacy (e.g., p-glycoprotein, glutathione, etc.), one would predict that high dose chemotherapy and therapy with some resistance modulating agents would increase therapeutic efficacy. Such "active" resistance would most likely generally arise from gene amplification or over expression, and would be characterized by a shoulder on the log response vs. dose curve, with eventual saturation of the protective mechanism. On the other hand, one would expect that high dose chemotherapy and most resistance modulating agents would be of little value for tumors with resistance due to defective apoptosis or due to a deficiency in or decreased drug affinity for a drug target, drug activating enzyme, drug active uptake system, or essential cofactor. Such "passive" resistance would most likely generally arise from gene down regulation, deletion, or mutation, and would probably be characterized by a relatively flat log response vs. dose curve, or by a curve in which a steep initial section is followed by a plateau, as target, etc., is saturated. (If response were plotted vs. log dose, then compared to the curve for a sensitive cell line, the curve for active resistance would be analogous to the pharmacodynamic curve seen with competitive antagonism [i.e., a sigmoid curve shifted to the right], and the curve for most types of passive resistance would be analogous to the pharmacodynamic curve seen with noncompetitive antagonism [i.e., a sigmoid curve with reduced maximal efficacy]. As such, one might also refer to active vs. passive resistance as competitive vs. noncompetitive resistance, respectively.) Many tumor types probably possess a combination of active and passive mechanisms of resistance. New in vivo strategies could be helpful in defining dose-response relationships, mechanisms of resistance, and targets for resistance modulation. Such in vivo studies would be conducted initially in animals, but might also be tested clinically if animal studies demonstrated them to be feasible and useful. These in vivo studies would be conducted by randomizing 5-25 subjects to one of 10-20 dose levels over a potentially useful therapeutic range. Nonlinear regression analysis would then be used to define the characteristics of a curve generated by plotting against dose the log percent tumor remaining after the first course of therapy. While this might offer insight into the nature of resistance mechanisms present initially, plotting further tumor shrinkage vs. dose-intensity vs. course number for each later treatment course (or plotting dose-intensity vs. time to tumor progression) might provide information on how tumors become increasingly resistant to drugs following treatment.