A critical evaluation of the mechanisms of action proposed for the antitumor effects of the anthracycline antibiotics adriamycin and daunorubicin

Although it was thought that apoptotic cells, when rapidly phagocytosed, underwent a silent death that did not trigger an immune response, in recent years a new concept of immunogenic cell death (ICD) has emerged. The immunogenic characteristics of ICD are mainly mediated by damage-associated molecular patterns (DAMPs), which include surface-exposed calreticulin (CRT), secreted ATP and released high mobility group protein B1 (HMGB1). Most DAMPs can be recognized by pattern recognition receptors (PRRs). In this Review, we discuss the role of endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) in regulating the immunogenicity of dying cancer cells and the effect of therapy-resistant cancer microevolution on ICD.

Immunogenic cell death and DAMPs in cancer therapy.

Accumulating evidence indicates that the innate and adaptive immune systems make a crucial contribution to the antitumour effects of conventional chemotherapy-based and radiotherapy-based cancer treatments. Moreover, the molecular and cellular bases of the immunogenicity of cell death that is induced by cytotoxic agents are being progressively unravelled, challenging the guidelines that currently govern the development of anticancer drugs. Here, we review the immunological aspects of conventional cancer treatments and propose that future successes in the fight against cancer will rely on the development and clinical application of combined chemo- and immunotherapies.

Immunological aspects of cancer chemotherapy.

Polyamines in rapid growth and cancer

Role of Polyamines in the Control of Cell Proliferation and Differentiation

Prostaglandins (PGs) have been implicated as possible modulators of the immune response and various inflammatory processes1–4. Various cell components of the immune system are sources of PGs, and mitogen or antigen stimulation of human or murine lymphocytes leads to their enhanced release5–8. They are also released from various human and animal tumours9,10. Thus, as cells of the immune system are both sensitive to and sources of PGs, these factors may be important as physiological immune regulators. For example, PGs of the E series are capable of inhibiting many effector functions9–15. They have also been shown to inhibit the development of the humoral response16,17. Although they inhibit the proliferative response to mitogens18,19, little is known about their effects on the development of the cell-mediated immune response to antigens. The data summarized here implicate PGs, thromboxane A2 (TXA2) and prostacyclin (PGI2) in the regulation of cellular immune responses at the inductive phase. Some of these data have been reported in abstract form20.

Prostaglandin modulation of development of cell-mediated immunity in culture

Background: Breast cancer treatments are most effective when initiated early, with very poor efficacy against metastatic disease. In seeking a readily metastasizing mouse breast cancer model to facilitate the search for effective therapies, E0771 medullary adenocarcinomas implanted subcutaneously in syngeneic C57BL/6 mice were studied. Materials and Methods: Standard pathological, histological and immunological methodologies were used. Results: The aggressive estrogen receptor-positive tumor invaded locally into the peritoneal cavity in 56% of mice, as well as metastasizing to the lungs in 52% of mice. The metastasis was a spontaneous event and immunosuppression was seen (e.g. generation of lyphokine activated killer cells and allogeneic cytotoxic T lymphocytes cytolytic activities ex vivo were suppressed). Other pathological events noted as the tumor progressed were: bloody ascites (56%) and shock (72%), both attributed to local (peritoneal) tumor invasion. Conclusion: The E0771 metastatic breast cancer model, which mimics the human disease, should be useful in testing new treatments against this disease and/or in examining the metastatic process. Each year in the United States over 210,000 new cases of breast cancer are diagnosed, resulting in almost 40,000

Distant metastasis from subcutaneously grown E0771 medullary breast adenocarcinoma.

Summary DBA/2 mice inoculated with the strain-specific leukemia L1210 survived more than 50 days as a result of the combined effects of drug treatments and immunity. Differences in L1210 immunogenicity were noted among 3 sublines of DBA/2 mouse strain. The therapeutic effects occurred also in DBA/2 sublines in which L1210 is weakly immunogenic and at drug doses which are immunodepressant per se . More than 60% of DBA/2 Ha-DD mice inoculated with leukemia L1210 survived longer than 50 days after combined treatments with 4,4′-diacetyl-diphenyl-urea-bis(guanylhydrazone)dimethanesulfonate and arabinosylcytosine. The cured mice were resistant to reimplantation of L1210. This resistance was transferred to mice previously not exposed to the leukemia by the inoculation of immune serum, spleen or lymph node cells. The thereapeutic effects against L1210 were reduced in preirradiated hosts. DBA/2 Ha-DD mice were sensitized against L1210 also by repeated immunization with X-ray-killed leukemic cells. The incidence of chemotherapeutically induced cures was about 20 and 5% in DBA/2J and DBA/2Cr mice respectively. Also, in these sublines the cured mice were immune to L1210. Synergism between drugs and either passive or adoptive immunity were seen in both DBA/2Cr and DBA/2Ha-DD mice inoculated with serum or spleen cells from hyperimmune DBA/2Ha-DD mice. Accelerated rejection of DBA/2J skin occurred in DBA/2Ha-DD mice immune to L1210. DBA/2Ha-DD mice could be sensitized against L1210 by immunization with DBA/2J or DBA/2Cr skin grafts. The survival of reciprocal skin grafts between DBA/2J and DBA/2Ha-DD mice was prolonged by the 2 drugs at doses exerting therapeutic effects against L1210. The antileukemic effects of the 2 drugs were reduced by pretreatments with the same drugs at therapeutic doses.

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Combined Effects of Chemotherapy and Immunity against Leukemia L1210 in DBA/2 Mice

Summary Spleen cell populations from mice treated with Adriamycin or daunorubicin were found to develop a greater complement-independent cellular cytotoxic immune response during culture with allogeneic tumor cells than spleen cells from untreated or cyclophosphamide-treated animals. A temporal and drug dose dependence of this effect was demonstrated. The changes in spleen cell population occurring in the donor mice consequent to drug treatment were evident in the nylon wool-adherent fraction of the spleen cells. The results are consistent with the possibility that the concentration of specific progenitor or accessory cells in the spleen is increased consequent to drug treatment.

https://cancerres.aacrjournals.org/content/canres/37/6/1719.full.pdf

Increased primary cell-mediated immunity in culture subsequent to adriamycin or daunorubicin treatment of spleen donor mice.

Increased ecto-5'-nucleotidase (ecto-5'NT) protein expression in several multidrug-resistant (MDR) cell lines, documented previously by our group, suggests that this enzyme is involved in drug resistance. Here, Northern blot analysis of selected cell lines and their MDR variants positively correlated ecto-5'NT protein with its mRNA expression. An inhibitor of ecto-5'NT enzymatic activity, alpha,beta-methyleneadenosine 5'-diphosphate (AMP-CP), was used to determine if functionally active enzyme had a role in drug resistance. AMP-CP (0.3 mM) reversed the resistance of ecto-5'NT-positive MDR cells (MCF7/A6, L1210/A) to doxorubicin, whereas it did not affect the doxorubicin sensitivity of the ecto-5'NT-negative parental cell lines or that of 2 ecto-5'NT-negative MDR cell lines (HL60/VCR and A2780/DX5). Furthermore, AMP-CP increased rhodamine uptake and inhibited rhodamine efflux from ecto-5'NT-positive MDR cells without affecting ecto-5'NT-negative MDR cells. The presence of exogenous adenosine (0.5 microM) circumvented AMP-CP-induced inhibition of rhodamine efflux from EL4/ADM cells. AMP-CP inhibited the growth of the ecto-5'NT-positive L1210/A MDR cells but had no effect on the growth of the parental cell line. Determination of intracellular ATP levels indicated that MDR cells which had increased ecto-5'NT expression also had a lower intracellular ATP level than their parental cells. Our results suggest that, in certain MDR cell lines, ecto-5'NT serves as a required accessory molecule in resistance mediated by ATP-dependent mechanisms and that growth-sustaining nucleosides are provided by this salvage pathway.

Enrico Mihich

Papers

Prostaglandin modulation of development of cell-mediated immunity in culture

Distant metastasis from subcutaneously grown E0771 medullary breast adenocarcinoma.

Combined Effects of Chemotherapy and Immunity against Leukemia L1210 in DBA/2 Mice

Increased primary cell-mediated immunity in culture subsequent to adriamycin or daunorubicin treatment of spleen donor mice.

Evidence for the involvement of ecto-5'-nucleotidase (CD73) in drug resistance