You will be shown a paragraph from a biomedical research article. Your task is to extract all drug combinations appearing in a specific sentence within in the paragraph. Each drug combination should be assigned to one of the following three categories:

- POS: Indicates a positive interaction between the drugs in the combination; for instance, drugs that have an additive or synergistic effect.
- NEG: Indicates a negative interaction between the drugs in the combination; for instance, combining these drugs might result in adverse side effects, or might reduce their efficacy.
- COMB: Indicates that the drugs are given in combination, but the type of interaction between the drugs cannot be determined based on the provided context.

Please format your answer as a json array. Each entry in the array should itself be an array formatted as [<drug_1>, <drug_2>, ..., <drug_n>, <category>] where <category> is one of the three categories listed above and <drug_1>, ..., <drug_n> are drug names copied verbatim from the input sentence. Different combinations may involve different numbers of drugs; in other words, the `n` in <drug_n> may vary.

As an example, the following output describes two extracted drug combinations; one between two drugs, and one between three drugs:

[["artesunate", "artemether", "COMB"], ["Nifedipine", "Labetalol", "Prazosin", "POS"]]

The paragraph and specific sentence are below. You should only extract relationships expressed in the specific sentence; the paragraph is provided for context.

In your output, return only the json array and no other text. If no drug combinations appear, return an empty array `[]`.

paragraph: Mitomycin C and doxorubicin elicit conflicting signals by causing accumulation             of cyclin E prior to p21WAF1/CIP1 elevation in human hepatocellular carcinoma             cells. Proteins involved in the G1 phase of the cell cycle are aberrantly expressed,             sometimes in mutated forms, in human cancers including human hepatocellular carcinoma.             Upon attack by a DNA-damaging anticancer drug, a cell arrests at the G1 phase;             this is a safety feature prohibiting entry of DNA-damaged cells into S-phase.             p21WAF1/CIP1 prevents damaged cells from progressing to the next cell cycle. Here,             we show that , in response to mitomycin C and doxorubicin , human hepatocellular carcinoma cells generate conflicting signals , mediated by cyclin E and p21WAF1/CIP1 , which respectively accelerates and represses cell cycle transition . Exposure to             these anticancer drugs led to rapid accumulation of cyclin E in both p53-proficient             HepG2 and p53-deficient Hep3B cells. Such anticancer drug-induced cyclin E accumulation             influenced the G1-S-phase transition, but not DNA fragmentation-mediated death.             In p53-proficient HepG2 cells, accumulation of cyclin E was followed by an increase             in the level of p53-dependent p21WAF1/CIP1, thereby inhibiting further the G1-S-phase             transition. Sublethal drug concentrations also induced rapid accumulation of cyclin             E, but p21WAF1/CIP1 accumulation was delayed, further facilitating the G1-S-phase             transition. Eventually, most cells arrested in G2/M. Thus, mitomycin C- or doxorubicin-induced             conflicting signals, mediated by cyclin E and p21WAF1/CIP1, are in play in human             hepatocellular carcinoma cells. Damaged G1 cells either immediately enter S-phase,             or do not do so at all, depending on the extent of DNA damage.

sentence: that , in response to mitomycin C and doxorubicin , human hepatocellular carcinoma cells generate conflicting signals , mediated by cyclin E and p21WAF1/CIP1 , which respectively accelerates and represses cell cycle transition .
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