Primary breast tumor levels of suspected molecular determinants of cellular sensitivity to cyclophosphamide, ifosfamide, and certain other anticanceragents as predictors of paired metastatic tumor levels of these determinants - Rational individualization of cancer chemotherapeutic regimens

Purpose: Cyclophosphamide is one of the most frequently used agents in the neoadjuvant, adjuvant, and high-dose chemotherapeutic treatment of breast c ancers. Preclinical models indicate that cellular sensitivity to cyclophosp hamide and other oxazaphosphorines, e.g., ifosfamide, is inversely related to the cellular content of two aldehyde dehydrogenases, viz ALDH1A1 and ALD H3A1, and glutathione. Breast tumor levels of these "determinants of cellul ar sensitivity to the oxazaphosphorines" are known to vary widely, and the decision as to whether or not to use an oxazaphosphorine as part of the the rapeutic strategy to treat breast cancer in any given patient is likely to depend, in large part, on the levels of these determinants in that cancer. ALDH1A1, ALDH3A1, and glutathione levels can be easily quantified in primar y breast tumors and in detectable metastatic breast tumors present in axill ary lymph nodes because the amounts of tissue required for the desired anal ysis can be readily obtained, whereas these levels cannot be quantified in residual metastatic breast cancer cell populations, i.e., those that escape detection and/or that are inaccessible to surgical harvest. The inability to directly quantify residual metastatic breast cancer cell ALDH1A1, ALDH3A 1, and glutathione levels would not preclude a rational decision with regar d to the inclusion/exclusion of an oxazaphosphorine as part of the chemothe rapeutic strategy intended to eradicate residual metastatic breast cancer c ells if primary breast tumor levels of these determinants reliably predicte d those in metastatic breast cancer cells. Methods: ELISAs and spectrophoto metric assays were used to quantify enzyme and glutathione levels in paired human primary and locally advanced metastatic breast tumor samples. Result s: Primary breast tumor ALDH1A1 and ALDH3A1 levels were highly predictive o f their respective levels in paired metastatic breast tumors present in axi llary lymph nodes (r(2) = 0.80 and 0.85, respectively). On the other hand, those of glutathione were relatively poorly predictive of its levels in pai red metastatic offshoots (r(2) = 0.35). Primary breast tumor levels of some additional enzymes known to catalyze the detoxification/toxification of va rious anticancer agents, though not of cyclophosphamide, were poorly predic tive (DT-diaphorase and glutathione S-transferases alpha, mu, and pi) or no t predictive (cytochrome P450 1A1) of their respective levels in paired met astatic offshoots. Conclusion: Since ALDH1A1, ALDH3A1 and, to a lesser exte nt, glutathione levels in primary breast tumors reliably predicted those in detectable and easily accessible metastatic breast cancer cell populations , viz those in axillary lymph nodes, they are also likely to be predictive of these levels in undetectable and/or relatively inaccessible metastatic b reast cancer cell populations. Thus, quantification of primary breast tumor ALDH1A1, ALDH3A1 and, to a lesser extent, glutathione levels prior to the initiation of not only neoadjuvant but also adjuvant and high-dose breast c ancer chemotherapy is likely to be of value in the rational design of indiv idualized chemotherapeutic regimens intended to eradicate breast cancer cel ls with a minimum of untoward effects.